americanmalacologists, mc.

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REGISTER OF AMERICAN MALACOLOGISTS

JANUARY 30. 1980

THE

NAUTILUS

ISSN 0028-1344

Vol. 94

No. 1

A quarterly

devoted to

malacology and

the interests of

conchologists

Founded 1889 by Henrj' A. Pilsbry. Continued by H. Burrington Baker.

Editor-in-Chief: R. Tucker Abbott

EDITORIAL COMMITTEE

CONSULTING EDITORS

Dr. Arthur H. Qarke, Jr.

Division of Mollusks

National Museum of Natural History

Washington, D.C. 20560

Dr. William J. Clench

Curator Emeritus

Museum of Comparative Zoology

Cambridge, Mass. 02138

Dr. William K. Emerson

Department of Living Invertebrates

The American Museum of Natural History

New York, New York 10024

Mr. Morris K. Jacobson

Department of Living Invertebrates

The American Museum of Natural History

New York, New York 10024

Dr. Aurele La Rocque

Department of Geology

The Ohio State University

Columbus, Ohio 43210

Dr. James H. McLean

Los Angeles County Museum of Natural History

900 Exposition Boulevard

Los Angeles, California 90007

Dr. Arthur S. Merrill

Woods Hole Biological Laboratory

National Marine Fisheries Service

Woods Hole, Massachusetts 02543

Dr. Donald R. Moore

Division of Marine Geology

School of Marine and Atmospheric Science

10 Rickenbacker Causeway

Miami, Florida 33149

Dr. Joseph Rosewater

Division of Mollusks

U. S. National Museum

Washington, D.C. 20560

Dr. G. Alan Solem

Department of Invertebrates

Field Museum of Natural History

Chicago, Illinois 60605

Dr. David H. Stansbery

Museum of Zoology

The Ohio State University

Columbus, Ohio 43210

Dr. Ruth D. Turner

Department of Mollusks

Museum of Comparative Zoology

Cambridge, Mass. 02138

Dr. Gilbert L. Voss

Division of Biologj'

School of Marine and Atmospheric Science

10 Rickenbacker Causeway

Miami, Florida 33149

Dr. Charles B. Wurtz

3220 Penn Street

Philadelphia, Pennsylvania 19129

EDITOR-IN-CHIEF

Dr. R. Tucker Abbott

American Malacologists, Inc.

Box 2255, Melbourne, Florida 32901

Mrs. Cecelia W.Abbott

Business and Subscription Manager

P.O. Box 2255

Melbourne, Florida 32901

Tlie Nautilus (USPS 374-980)

ISSN 0028-1344

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THE

NAUTILUS

Volume 94, number 1 — January 30, 1980

ISSN 0028-1344

ERRATUM: The running heads at the top of the page in the last, October 1979,

issue should have read Vol. 93 not 94. Further, the species names in the table of

contents should not have been capitalized. The printer and editor apologize.

CONTENTS

Short Papers

I. S. Khomasurya

Pleuroploca aurantiaca (Lamarck) (Fasciolariidae) in the Grenadines, Lesser Antilles 1

Clement L. Counts, in

Rangia cuneata in an Industrial Water System (Bivalvia: Mactridae) 1

Artie L. Metcalf

Fossil Rangia cuneata (Mactridae) in Eddy County, New Mexico 2

Fred G. Thompson and Jane E. Deisler

The Introduction of the Land Snail Alcadia striata (Lamarck)

into Miami, Florida 3

Samuel L. H. Fuller and Raymond H. Hartenstine

Anodonta imbecUlus Say (Bivalvia: Unionidae) in the Delaware

River Basin 4

Eva Pip

Somatogyrus (Gastropoda: Hydrobiidae) in Lake Winnipeg, Canada 4

Lynn B. and Wayne C. Stames

Discovery of a New Population of Pegias fabula (Lea) (Unionidae) 5

E. J. Petuch and M. G. Harasewych

Distorsio kurzi a New Cymatiid Gastropod from the Central Philippines 6

J. K. Buttner and R. C. Heidinger

Seasonal Variations in Growth of the Asiatic Clam, Corbicula Jluminea

(Bivalvia: Corbiculidae) in a Southern Illinois Fish Pond 8

Victor Scarabino

Cadulus tetraschistus (Watson), an Earlier Name for C. quadridentatii^

(Dall) and C. incisits Bush (Scaphopoda) 11

Ralph W. Taylor

Mussels of Floyd's Fork, a Small Northcentral Kentucky Stream (Unionidae) 13

Artie L. Metcalf

A New Fossil Radiocentrum (Pulmonata: Oreohelicidae) from Northern

Coahiula, Mexico 16

Thomas R. Piatt

Observations on the Terrestrial Gastropods in the Vicinity of Jasper,

Alberta (Canada) 18

Charles M. Cooper and V. Wayne Johnson

Bivalve Mollusca of the Yalobusha River, Mississippi 22

David H. Kesler

Seasonal Abundance of Amnicola limosa (Hydrobiidae) Egg^ and

Individuals in a Rhode Island Pond 25

H. Lee Fairbanks

Morphological Notes on Oreohelix amariradix Pilsbry, 1934

(Pulmonata: Oreohelicidae) 27

John F. Wehmiller and William K. Emerson

Calibration of Amino Acid Racemization in Late Pleistocene

Mollusks: Results from Magdalena Bay, Baja California Sur, Mexico, with

Dating Applications and Paleoclimatic Implications 31

Deaths 10 Publications Received 37

Announcing a New Scientific journal

MONOGRAPHS OF MARINE MOLLUSCA

Taxonomic revisions of the living and

Tertiary marine Mollusca of the world

Edited By R. Ti'cker Abbott

Monographs of Marine Mollusca is a professional journal devoted to the systematics,

biology, zoogeography and taxonomy of marine mollusks, both living and fossil. It is

issued with color plates and in a convenient looseleaf form compatible with the former

Indo-Pojcific Mollusca. Subscribers to the latter should make certain they now apply for

the continuing editorial production of the editor, Dr. R. T. Abbott. Numbers are issued

irregularly as research is completed. Number 1 is "The Family Cerithiidae in the Indo-

Pacific" by R. S. Houbrick of the Smithsonian Institution. Numbers in preparation in-

clude the Mitridae by W. 0. Cemohorsky, and the family Buccinidae in the Indo-Pacific.

Subscribe by writing American Malacologists, Inc.. P. 0. Box 2255, Melbourne, FL 32901.

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STATEMENT OF OWNERSHIP, MANAGEMENT AND CIR-

CULATION (Required by) Act of October 23, 1962: Section

4396. Title 39. United States Code, and postal regulation

132-622.

1. Title of publication: THE NAUTILUS.

2. Date of filing, September 25, 1979

3. Frequency of Issue: Quarterly (4 per year).

4. Location of known office of publication: 2208 South

Colonial Dr., Melbourne, FL 32901.

5. Location of the Headquarters of General Business

Offices of the Publishers: 2208 South Colonial Dr.,

Melbourne, FL 32901.

6. Names and addresses of publisher, editor, and

managing editor: Publisher, American Malacologists,

Inc., P.O. Box 2255, Melbourne, FL 32901. Editor, R.

Tucker Abbott, P.O. Box 2255, Melbourne, FL 32901.

Business Manager, Mrs. Cecelia W. Abbott, P.O. Box

2255. Melbourne, FL 32901.

7. Owner: American Malacologists, Inc.. P.O. Box 2255,

Melbourne, FL 32901.

8. Known bondholders, mortgages, and other security

holders owning or holding 1 percent or more of total

amount of bonds, mortgages or other securities:

none.

Extent and Nature of Circulation:

I certify that the statements made by me above are cor-

rect and complete,

(signed) R. Tucker Abbott, Editor

Vol. 94(1)

January 30, i;»S()

THE NAUTILUS 1

SHORT PAPERS

PLEUROPLOCA AURANTIACA (LAMARCK)

(FASCIOLARIIDAE) IN THE GRENADINES,

LESSER ANTILLES

L S. Khomasurya

Carriacou Marine School

Canadian Junior College

Carriacou, Grenada

The Caribbean molluscan faunal province ex-

tends south to Brazil, (Abbott, 1968). However, no

specimen of Pleuroploca auranti(w.a has been

reported in the Caribbean Sea area. In fact, the

species is considered to be endemic to Brazil,

with its range extending from Espirito Santo to

Amapa, Brazil, (Rios, 1975).

Recently, two live specimens were collected by

Mr. James Whitney and myself, in Carriacou, an

island 32 km north of Grenada, (3,000 km from

Amapa), one at Windward Reef, January, 1978,

FIG. 1. Pleuroploca aurantiaca (Lamarck} from Windward

Reef. Camacou. collected by Mr J. Whitney at 13 m depth on

Janiuiry 1978; and photographed by Mr K. Pitcher. 150 mm.

and the other at the Sunset Beach area, March,

1978, at depths of approximately 13 m. On fur-

ther inquiry, it was learned that other specimens

have also been found in Grenada at Westerhall

Bay and Calivigny Island, Grenada (D. L. N. Vink

and D. Willcox, personal communications). This

species has not, as yet, been reported from the

TrinidadA"obago region, the chain of islands con-

necting South America and the Grenadines.

Both Carriacou Island shells were adult speci-

mens, measuring approximately 150 mm in

length. The shell resembles Pleuroploca gigantea

(Kiener) in outline, but has a more prominent

shoulder and numerous spiral cords bearing

heavy beads. The most distinguishing feature is

the color of the live soft parts, which are not red,

as in P. gigantea, but are light-tan with

numerous rectangular markings of bright

torquoise-blue.

LITERATURE CITED

Abbott, R. T. 1968. SeasheUs of North America. Golden Press,

New York.

Rios, E. C. 1975. Brazilian Marine Mollusks Iconography, Fun-

dacao University Rio Grande, Brazil.

RANGIA CUNEATA IN AN INDUSTRIAL

WATER SYSTEM (BIVALVIA: MACTRIDAE)

Clement L. Counts, III

College of Marine Studies

University of Delaware

Lewes, Delaware 19958

Rangia cuwata (Sowerby, 1831) is commonly

found in fresh and brackish coastal waters from

Chesapeake Bay to Texas (Abbott, 1974). The

northernmost extension of its range has been

reported as the upper reaches of the Chesapeake

Bay where severe winter temperatures have

caused mass mortalities (Gallagher and Wells,

1969). The present report records for the first

time the presence of R. cuneata in Delaware Bay.

Adult specimens of this clam were collected

from the water system of the Getty Oil Refinery,

Delaware City, New Castle County, Delaware,

2 THE NAUTILUS

January 3(1, 1980

Vol. 94(1)

during May 1979. The clams were discovered by

employees during a minor fire when nozzle

pressure of the fire hoses was significantly

reduced. When the nozzle was removed, adult R.

cuneata fell from the fire hose.

The source of the water for the refinery's

water system is the Delaware River. Water is

pumped through a 40.64 cm screened intake pipe

and then pumped to a 3,103,700 liter tank which

serves as a reservoir for the fire and cooling

systems. Pipes in these systems range from 7.62

cm to 40.64 cm in diameter. The water in the

pipes is usually treated three times a day by slow

feed (25 min) hypochlorination which leaves a

residual free chlorine level of less than 3 ppm in

the water. Invasion of the system was attributed

to a breakdown of the chlorination system during

the late spring of 1978. It thus appears that R.

cuneata has tolerated this concentration of

chlorine, although no data is available to indicate

its effects on the survival of larvae in the water

system.

The appearance of R. cuneata in Delaware Bay

may have resulted from clams migrating through

the Chesapeake-Delaware Canal which connects

northern Chesapeake Bay with Delaware River

upstream of the oil refinery. The present paper is

also the first to report R. cuneata as a biofouling

nuisance. The circumstances in which R. cuneata

were collected is a striking parallel to problems

usually associated with Corbicula (Ingram, 1956;

Sinclair, 1971).

The author wishes to thank Dr. R. Tucker Ab-

bott for confirming the identificatiort of the

species and Dr. Melbourne R. Carriker for his

review of the manuscript. University of Dela-

ware, College of Marine Studies Contribution No.

142.

LITERATURE CITED

Abbott, R. T. 1974. American Seashells. 2nd Ed. Van Nostrand

Reinhold, New York. (Ki pp.

Gallagher, J. L.. and H. W. Wells. 1969. Northern range ex-

tension and winter mortality of Rangia cuneata. The

NautiluxS3{\y.-22-Z^.

Ingram, W. M. 19.56. Snail and clam infestation of drinking-

water supplies. Jour. Amer Water Wurks Assoc.

48(3):2.W-268.

Sinclair. R. M. 1971. Corhieukt variation and parallels.

fi(o/(«/w/ (Virginia) 53(2):1.5,3-159.

FOSSIL KANGIA CUNEATA (MACTRIDAE)

IN EDDY COUNTY. NEW MEXICO

Artie L. Metcalf

Department of Biological Sciences

University of Texas at El Paso

El Paso, Texas 79968

Presence of fossils of the brackish water, mac-

trid clam Rangia cuneata (Sowerby. 1831), in

southeastern New Mexico was noted by Andrews

(1977:220). Herein, more specific information con-

cerning these occurrences is provided.

Shells (Figs. 1, 2) have been taken at three

localities (listed below) along the Pecos River,

east of Malaga, Eddy County. At none of these

places were shells found in situ in sediments;

however, it seems most likely that they were

derived from gravel deposits of Pleistocene age.

At Localities 2 and 3 shells were found where

quarrj'ing operations had been carried out in

gravels of stream-flanking terraces. These gravels

are clearly older than inset, Holocene sediments

(predominantly silts) and seem likely to be of

Pleistocene age. At Locality 1 shells were found

in gravels of various sources and ages (Holocene

and Pleistocene) along the floodplain of the Pecos

River.

Most shells have a limonitic-stained rind of

calcium carbonate, especially on their inner sur-

face (Fig. 2) and all are judged to be fossil. No

fresh shells have been found here or elsewhere

along the Pecos River. Shells collected range from

31 to 42 mm in length.

Occurrence of this estuarine clam so far inland

FIGS. 1-2. F(i.<sit Rangia t'uneata (Sowerby) from Liealilii 1

(see text), Eddy County. New Mexico.

Vol. 94(1)

January 30, 198n

THP] NAUTILUS 3

is unexpected. The nearest populations are on the

Texas coast some 800 km to the southeast. There,

Andrews (1977:220) noted that R. cuneatn is a

brackish water species that has been found a few

miles up the Nueces River. Hopkins et al

(1973:220) found that R. cuneata is usually

restricted to estuarine environments because of

(1) larval requirements of salinities between 2

and 10 ppt and (2) necessity for salinity changes

as a stimulus to induce spawning.

In the area of Malaga Bend (of the Pecos

River) where these specimens were taken,

numerous springs and seeps contribute a salty

brine to the Pecos River. The brine is produced in

Upper Permian (Ochoan) strata at the base of the

Rustler Formation where its waters contact and

dissolve salts of the underlying Salado Forma-

tion. Artesian pressure brings the brine upward

in the Malaga Bend area (Robinson and Lang,

1938:86-90). In one study (McClure, 1938:75) it

was found that there was, in river waters in the

12 km between Malaga and Pierce Crossing gaug-

ing stations, an increment of total dissolved

solids of "about 420 tons per day of which about

eighty percent or 340 tons was common salt."

Although conditions of salinity were seemingly

not inimical to R. cuneata in this short segment

of the Pecos River, the question of how it could

have dispersed so far inland is difficult to

answer. Movement upstream through the fresh

waters of the Rio Grande and lower Pecos River

seems unlikely and the area has been far from

the sea throughout Tertiary time. Transport by

waterfowl seems the most plausible hypothesis to

account for this occurrence. An avian transport

hypothesis has been advocated by Bachhuber

(1977:263-265) to account for presence of

foraminifera in Quaternary deposits of Pluvial

Lake Estancia in central New Mexico. There are

other reports of organisms with marine or

brackish water affinities occurring far inland in

this region. These include several species of

gastropods, occurring as fossils, found by Dr.

Dwight W. Taylor farther downstream in the

Pecos River drainage in Terrell County, Texas

(Andrews, 1977:92, 98, 180). Creel (1964:236-240)

reported the extraordinary occurrence of a

marine, grapsoid crab and "a barnacle" in salt

springs at Estelline, Hall County, Texas, in the

Red River drainage.

LOCALITIES OF COLLECTIONS

All localities are along the Pecos River, Eddy

County, New Mexico.

1. 32°12'37"N; 104°0r42"W. SE corner. Sec. 13,

T. 28 S, R. 29 E. 3.7 km E and 1.6 km S of

Malaga. (4 shells).

2. 32°13'05"N; 104°00'05"W. SE'4, SE'/4, NE'/4,

Sec. 17, T. 24 S, R. 29 E. 6.5 km E and 0.9 km S of

Malaga, immediately dowTistream from Fishing

Rock (an island in river). (5 shells).

3. 32°11'20"N; 103''58'37"W. SE>/4, SW'/^,

NWy4, Sec. 27, T. 24 S, R. 29 E. On SE side of

Pecos River at Pierce Canyon crossing. (3 shells).

LITERATURE CITED

Andrews. J. 1977. Shells and shores of Texas. Univ. Texas

Press, Austin, xx -I- 365 pp.

Bachhuber, F. W. and W. A. McClellan. 1977. Paleoecology of

marine Foraminifera in the Pluvial Estancia Valley, cen-

tral New Mexico. Qmt. Res. 7:254-267.

Creel, G. C. 1964. Hemigrapsus estellinensis: a new grapsoid

crab from North Texas. Southwest. Natur. 8:2.36-241.

Hopkins. S. H., J. W. Anderson and K. Horvath. 1973. The

brackish water clam Rangia cuiwata as indicator of

ecological effects of salinity changes in coastal waters. U.S.

Army Eng. Waterways Exp. Sta. Contract Rep. H-73-I:xi

+ 1-250.

McClure, T. M. (Ed.). 1938. Water quality, Pecos River. Bien.

Rep State Eng.. New Mexico 12/13:62-75.

Robinson, T. W. and W. B. Lang. 1938. Geology and ground-

water conditions of the Pecos River Valley in the vicinity

of Laguna Grande de la Sal, New Mexico, with special

reference to the salt content of the river water. Bien. Rep.

State Eng.. New Mexico 12/13:79-100.

THE INTRODUCTION OF THE LAND SNAIL

ALCADIA STRIATA (LAMARCK) INTO

MIAMI, FLORIDA

Fred G. Thompson

Florida State Museum

University of Florida

Gainesville, FL 32611

and

Jane E. Deisler

Florida State Division of Plant Industries

13603 Old Cutler Road

Miami, FL 33158

4 THE NAUTILUS

January :?(!. UWO

V.il.Hldl

A Puerto Rican snail, Alccidia striata Lamarck

(Prosobranchia, Helicinidae) has been introduced

in Miami, Florida, where at least one breeding

population is established. The species was

discovered at the Sunlan Aquatic Nursery, 8301

NW 8 St. by plant inspectors from the Florida

State Division of Plant Industry (FSDPI). It is

abundant on the nursery grounds and on im-

mediately adjacent properties. By now it prob-

ably has been introduced, via nursery stock, into

other places within the greater Miami area. The

nursery has imported ornamental plants from

Puerto Rico for about 22 years, from where the

snail probably was introduced on nursery stock.

We wish to thank Curtis F. Dowling and

Lionel Stange (FSDPI) for bringing to our atten-

tion this introduction. Voucher specimens are

deposited in the Florida State Museum (UF

25239, 25240).

ANODONTA IMBECILLIS SAY (BIVALVIA:

UNIONIDAE) IN THE DELAWARE RIVER

BASIN

Samuel L. H. Fuller

Academy of Natural Sciences of Philadelphia

Philadelphia, Pennsylvania 19103

and

Raymond H. Hartenstine

Jack McCormick & Associates

860 Waterloo Road

Devon, Pennsylvania 19333

Anodonta imbecillis Say is among the

geographically more widely distributed of Nearc-

tic naiades, but in the Atlantic drainage it has

understandably been considered only a southern

species: in a recent comprehensive account, for

example, Johnson (1970, Bulletin of the Museum

of Comparative Zoology, 140:362-364) recorded

this species from no farther north in that

drainage than the Gunpowder River basin in

Maryland. However, we recently (5 June 1976, 5

June 1977) secured numerous A. imberillis in

Pickering Creek of the Delaware River basin in

Chester County, Pennsylvania.

This unexpected extension of geographic range

raises the question of the antecedents of these

animals. Ih they represent an overlooked natural

population or an inadvertent introduction by

man'.' We infer the success of the Pickering Creek

p<jpulation from our having observed gravid

females and several age-classes (i.e., reproduction

and recruitment). Had there been natural suc-

cessful populations in the Philadelphia, Penn-

sylvania, area, the assiduous local investigators of

the last 150 years (e.g., William D. Hartman and

Isaac Lea) would probably have found them. Con-

sequently, we suspect that the Pickering Creek

population was inaugurated by man, but have not

as yet gained the necessary information (if ex-

tant) regarding the presumed age of the popula-

tion and the time(s) of introduction(s) of host

fishes suitable for larval parasitism by Anodonta

imbecillis. Further investigation of this and other

points of interest concerning this population is

underway, and the results will be reported.

Constructive criticism of an early version of

this note was offered by Robert C. Bullock of the

University of Rhode Island at Kingston.

somat(x;yrus (gastropoda: HYDROBI-

idae) in lake winnipeg, canada

Eva Pip

Department of Botany

University of Manitoba

Winnipeg, Manitoba

Canada R3T2N2

The genus Somatogyrus consists of numerous

species whose distributional focus lies in the

southeastern United States. Some species have

spread within the Mississippi River drainage, and

a single species, S. subglobosus (Say), occurs as

far north as the Great Lakes, and the St. Law-

rence and Ottawa Rivers (La Rocque, 1968).

Neither living nor fossil material of this genus

has been reported from areas west or north of the

Great Lakes.

Specimens of a Somatogyrus species (Fig. 1)

were collected at Victoria Beach, on the southeast

shore of Lake Winnipeg (50''44'N, 96°36'W) in

September of both 1976 and 1978. Although the

shells were empty, their relatively fresh condition

suggested the existence of a living population off-

shore. The area is characterized by a sand bottom

Vol. 91(1)

Januarv^O, 1980

THE NAUTILUS 5

FIG. 1. Somatogyrus sp. from Lake Winnipeg. A, /.■? mm. B,

6.0 mm.

strewn with large rocks exposed to heavy wave

action and contains submerged stands of Pota-

mogeton richardsonii, P. pectinatus and

Myriophyllum exalbescens, which are populated

by a variety of other amnicolids, as well as

Campeloma decisum Say and by pulmonates. The

water chemistry at this site averaged a total

filtrable residue value of less than 150 mg/1, a

total alkalinity value of less than 100 mg/1

CaCOa, and chloride, nitrogen and phosphorus

levels of less than 5 mg/1 respectively, although

sulphate values were as high as 30 mg/1.

The origin of this taxon in Lake Winnipeg is

problematic. The Great Lakes system was con-

fluent with Lake Agassiz during Pleistocene

times, and the former is at present connected

wath the Winnif)eg River-Rainy River system at

Saganaga Lake (48°15'N, 90°55'W) (Clarke, 1973).

However surveys by Clarke (1973) and Pip (1978)

failed to find Somatogyrus in the waters of the

Winnipeg and Rainy River system. The record

nearest to Lake Winnipeg (Pip, 1978) is based on

a specimen from Itasca Co., Minnesota, in the

Mississippi River drainage system. Furthermore,

the Lake Winnipeg species is not the lirate-

apexed S subglobosus, but has a punctate apex

and appears to be more closely related to S. in-

teger (Say) which is known from the region south

of the Great Lakes, and to S. depressiis (Try on)

from Wisconsin.

Whether the Lake Winnipeg population is in-

digenous or the result of recent accidental in-

troduction, its apparent establishment presents a

substantial range extension for the genus in

North America.

LITERATURE CITED

Clarke. A. H. 1973. The freshwater molluscs of the Canadian

Interior Bas\n. Maku-<ihiyin 13:1-509.

La Rocque, A. 1968. Pleistocene MoUusca of Ohio. Ohio I)iv.

Geol. Survey, Bull. 62, Part 3. 357-553. (p. 402).

Pip, E. 1978. A survey of the ecology and composition of

submerged aquatic snail-plant communities. Can. Jour. Zooi

56:2263-2279.

DISCOVERY OF A NEW POPULATION OF

PEGIAS FABULA (LEA) (UNIONIDAE)

Lynn B. Starnes

Tennessee Valley Authority

Division of Forestry, Fisheries,

and Wildlife Development

Norris, Tennessee 37828

and

Wayne C. Starnes

University of Tennessee

Department of Zoology

Knoxville, Tennessee 37916

Simpson (1914) lists the distribution of Pegias

fabula (Lea, 1838) as the Tennessee and

Cumberland River drainages. It appears to be

restricted to small, high-gradient tributaries of

these drainages (Ortmann, 1918). Stansbery

(1976) has proposed Pegias for endangered status

and has indicated that a few additional previous-

ly unknown populations may be discovered in

smaller tributaries.

On October 22, 1977, five gravid females of

Pegias fabula were collected by the authors at

Freedom Church Ford on the Little South Fork

Cumberland River approximately 8 km north of

Ky 92 crossing, Wayne County, Kentucky [Ohio

State University Museum (OSUM) 41308 (3), W.

C. Starnes CU/BS-2 (2)]. The individuals collected

were of rather uniform size ranging from 24.1

mm to 26.7 mm in length and 14.3 mm to 16.7

mm in height. In addition to these live in-

dividuals, numerous valves were also collected in-

dicating a substantial population. Additional

specimens of similar dimensions were collected by

A. and C. Bogan (University of Tennessee) at the

same locality on October 30, 1977 [OSUM 41309

(6)].

6 THE NAUTILUS

Januarv '-M). 198fl

Vol. 91(1)

The Little South Fork Cumberland River at

Freedom Church Ford is approximately 20-25 m

wide. Except for its clear, cold water, it does not

assume headwater characteristics described as

typical habitat for Pegias. While riffles are pres-

ent in the area where Pegias was collected,

there are extensive reaches of pool areas. All

Pegias specimens were collected from the transi-

tion zone at the tail of a long sluggish pool just

at the point where water velocity suddenly in-

creased (about 0.2 m/sec) to enter a turbulent rif-

fle below. Water depth averages about 20 cm at

low river stages. Substrate was predominately

dark sand with scattered small gravel. Pegias oc-

curred either partly buried or on the substrate

with only the foot penetrating the sand. The

periostracum of all individuals had been largely

eliminated, apparently from the abrasive action

of sand in the current-swept habitat. Similar

massive erosion was noted on all specimens ex-

amined from several other localities (University

Michigan Museum of Zoology, 70152, 23144, 23151,

58872, 105467, 29085, 105469 through 105477). In

close association with Pegias were Ptychobran-

chus subtentum and Corbicula manilerisis. Oc-

curring elsewhere in the riffle were Ptycho-

branchus fasciolare, EJliptio dilatatiis, Medio-

nidus conradicus, Villosa iris, V. taeniata, V.

vanuxemi, Lampsilis fasciola, and Fusconaia

subrotunda.

Additional Pegias valves have been collected at

Ritner Ford 3.2 km upstream from Freedom

Church Ford [WCS CU/BS-1 (2)] indicating that

the Little South Fork population is widespread in

riffle areas of the river. The Little South Fork

originates in Pickett County, Tennessee, and

stretches some 41.6 km along the Wayne/Mc-

Creary County line in Kentucky to its confluence

with the Big South Fork Cumberland River. Con-

siderable additional habitat may be extant

upstream from Ritner Ford. However access to

this area is limited and it has not been assessed

thus far. The Little South Fork is perhaps the

most pristine stream remaining within the entire

known range of Pegias in the Cumberland and

Tennessee drainages.

While analogous habitat occurs in the Big

South Fork Cumberland River, additional popula-

tions are not expected there. In recent years, in-

creases in coal surface mining has increased silta-

tion and decreased water quality to the point

that the mollusk population is declining rapidly

and will perhaps soon disappear.

The discovery of a substantial and perhaps the

healthiest, population of Pegias fabuLain the Lit-

tle South Fork Cumberland River constitutes a

significant addition to the known distribution of

this rare mollusk. If the Little South Fork, which

is designated a Kentucky Wild River, continues

to enjoy protection from strip mining and other

perturbations, its mussell population should be

afforded continued preservation. This suggests

that perhaps the status of Pegias should be

regarded as threatened rather than endangered.

We thank David H. Stansben,'. OSUM, for

provision of information and deposition of

specimens.

UTERATURE CITED

Lea, Isaac. 1838. Observations on the Genus Unio together

with descriptions of new genera and species in the families.

Naiades. Colimacea, Lymnaeana, Melaniana, and Peristo-

miana. 2:1-152. Privately published, Philadelphia. Penn.

Ortmann, Arnold E. 1918. The nayades (freshwater mussels)

of the upper Tennessee drainage. With note on synonymy

and distribution. Proc. Amer. Philos. Soc. 57(6); 521-626.

Simpson, Charles T. 1914. A descriptive catalogue of the

naiades, or pearly freshwater mussels. Detroit. Privately

published by Bryant Walker. 1-1540.

Stansbery. David H. 1976. Status of endangered fluviatile

mollusks in Central North America. Peguw: fahtila (Lea.

1838). U.S. Dept. of Interior. Fish and Wildlife Service. RF

3712. p. 1-6.

DISTORSIO KURZI. A NEW CYMATIID

GASTROPOD FROM THE CENTRAL

PHILIPPINES

E. J. Petuch

Rosenstiel School of Marine

and Atmospheric Science

4600 Rickenbacker Causeway

Miami, Florida 33149

and

M. G. Harasewych

College of Marine Studies

University of Delaware

Newark, Delaware 19711

Over the last few years there has been in-

creased interest in commercial shell collecting in

the deeper waters of the central Philippines. This

.94(1)

January :?(), 19S0

THE NAUTILUS 7

FIGS. 1-2. Distorsio (Rhysema) kurzi new spedes. 1, Holotype. USNM 783780, off Balicasag, Bohol Island, Philippines, in

120-150 meters (1 X). 2, Pamtype. USNM 783931. same locality and depth (1 X).

has brought to light many new and unusual

species from previously unsampled offshore com-

munities. Among these is a new Cymatiidae

species of Distorsio described herein.

Distorsio (Rhysema) kurzi new species

Figs. 1 and 2

Description: Shell to 56 mm; spire angle

45° -50°; protoconch with 2 whorls, smooth, glassy;

teleoconch with 7-9 whorls; first 4 whorls conical;

b^inning with 5th whorl there is a swollen bulge

with the parietal shield 180° in apposition, unit

arrangement repeating every 270°; shell strongly

sculptured with beads or ribs at intersections of

spiral cords and axial ribs; spiral sculpture con-

sists of 1 major cord at the suture, 1 at the

sharply angled shoulder (comprising 8 coalescing

threads), 5 major cords below the shoulder, and 4

or 5 on the siphonal canal. Shell color deep

golden brown with darker brown bands at the

shoulder and the suture; parietal shield thin, len-

ticular, coffee to orange-brown in color, with

white denticulations; 8 denticles on inside of

outer lip; anterior 5 produce white denticles on

outer lip with white chevrons between; 6th denti-

cle greatly enlarged, protruding into aperture op-

posite corresponding indentation in columella;

13-16 white denticles on columellar side of

siphonal canal below the indentation.

Ti/pe material: Holotype — United States Na-

tional Museum (USNM 783780), length 51 mm;

paratypes in the United States National Museum,

Washington, D.C. (USNM 783931).

Type locality: Off Balicasag, Bohol Island,

Philippines, in 120-150 meters.

Range: Known only from the type locality.

Discussion: This new species is a component of

the lower continental shelf communities that sur-

round the deep water pockets between the islands

of the central Philippines. Distorsio kurzi most

closely resembles the Japonic D. constricta habei

(Lewis, 1972:38-44, figs. 38, 39) but differs

primarily by having a sharply angled shoulder

that produces the characteristic pronounced

humps. The new species is more darkly colored

than D. constricta habei being consistently

golden brovm, with a darker mid-body band,

brown parietal shield and outer lip, as opposed to

the pale-tan to white body color and white

parietal shield of D. constricta habei. The number

of denticles on the columellar edge of the

siphonal canal also consistently differs between

the two species; 8-12 in D. constricta habei and

13-16 in Z). kurzi.

The new taxon honors Richard M. Kurz,

Wauwatosa, Wisconsin, who first recognized the

species as new and donated the type material.

LITERATURE CITED

Lewis, H. 1970. Notes on the genus Distorsio (Cymatiidae)

with descriptions of new species. The Nautilus 86:27-50.

8 THE NAUTILUS

January .•^), 1980

Vol. 91(1)

SEASONAL VARIATIONS IN GROWTH OF THE ASIATIC CLAM,

CORBICULA FLUMINEA (BIVALVIA: CORBICULIDAE)

IN A SOUTHERN ILLINOIS FISH POND

J. K. Buttner and R. C. Heidinger

Qx)perative Fisheries Research Laboratory

Southern Illinois University

Carbondale, Illinois 62901

ABSTRACT

Fifty specimens of the Asiatic clam were stocked into a 0.06 ha fish pond for 62

days during the summer, and UO days for both fall and muter. Clam recovery for

summer, fall, and winter observations was 82%, 60%, and 98%, respectively. Gam

growth rates for summer and fall averaged 0.012 mm/day and 0.05i g/day. while

vnnter growth rates averaged 0.003 mm/day and 0.0003 g/day. Summer and fall

growth rates were not significantly different (P = 0.29). while winter growth rates

were significantly lower (P = 0.001). Relative weight gain per day for all observa-

tions was significantly greater (P = 0.01) for smaller clams. Absolute weight gain

per day was significantly greater fP = 0.006) for larger clams during the summer,

while fall and winter absolute growth was similar for all clams. Summer, fall, and

winter water temperatures were significantly different (P = 0.001), while

phytoplankton density remained relatively constant for all observations.

INTRODUCTION

Corbicula fluminea (Miiller)' was first collected

in the United States from the Columbia River,

Washington in 1938. Subsequently it has become

established in all river drainage systems except

the Great Lakes and Northeast (Sinclair and

Isom, 1963; Sickel, 1976; and Gardner, et at.

1976). Presently Corbicula is considered a

nuisance, possible subplanting native mollusks,

causing economic problems in irrigation canals

and power generating plants, and exhibiting

periodic dieofife (Sinclair and Isom, 1963; Bickel,

1966; and Sickel, 1976). Although the ecological

preferences, range, and economic importance of

Corbicula are well-documented by Heinsohn

(1958); Sinclair and Isom (1963); and Rinne

(1974), the biology of the clam itself is poorly

known. Few studies exist on Corbicula growth

rates and none on seasonal variations in growth

(Sinclair and Isom, 1%3; Rinne, 1974; O'Kane,

1976; and Sickel, 1976). The purpose of this in-

vestigation was to determine daily and seasonal

growth rates of Corbicula, and effects of clam size

' Also known as Corbicula manilensis (Philippi) and leana

Lea.

on absolute and relative growth rates in a south-

ern Illinois fish pond.

MATERIALS AND METHODS

Fifty specimens of Corbicula were labeled with

nail polish, measured to the nearest 0.1 mm, and

weighed to the nearest 0.01 g. Linear values were

obtained from length measurements and weight

values after test clams were cleaned and blotted

dry. Two open top cages, each 0.3 m^ and 9 cm

deep, were filled to a depth of 3 cm with

sutetratum obtained from the test pond. Twenty-

five clams were placed on the substratum of each

cage and stocked into a 0.06 ha pond (Table 1).

Cages containing clams were placed on the pond

substratum in 0.5 m water. Summer, fall, and

winter runs were initiated on 20 July, 22 Oc-

tober, and 6 December, respectively. Surface

water temperatures were recorded between 0700

and 0900 daily. Phytoplankton samples were col-

lected with an integrated column sampler, fixed,

preserved, identified, and counted as described by

Vollenweider (1969). Upon termination of each

run recovered clams were measured to nearest 0.1

mm and weighed to nearest 0.01 g. all statistical

examinations were by multiple regression

analysis.

Vol. 94(1)

January 30, 1980

THE NAUTILUS 9

TABLE 1. Summary ((/(brbicula stockim/ data for all observatinns.

Parameter

Summer

Fall

Winter

No. Clams Stocked

Wt. Clams Stocked (g)

Ln. Clams Stocked (mm)

Density Stocked (No./m )

Density Stocked (g/m^)

Duration of Run (days)

50 50

0.95-8.15 1.14-9.34

14-29 15-30

78 78

256 273

62 40

50

1.28-11.10

15-32

78

299

40

' Ln. equals length.

RESULTS AND DISCUSSION

Low recovery of clams during the fall was very

likely due to muskrat predation (Table 2).

Muskrat tracks were found along the shoreline

and digging marks observed in the substratum of

test cages. Clams not recovered were lost, no

labeled empty shells were collected. Surface

water temperatures were significantly different

for all seasons, while phytoplankton numbers re-

mained relatively constant (Table 2). Phyto-

plankton was dominated by chlorophytes in sum-

mer and chrysophytes in winter. Fall phyto-

plankton populations were dominated by varying

ratios of chlorophytes and chrysophytes.

Corbicula grew throughout the year, even in

winter when water temperatures averaged 3.0° C.

The presence of a crystalline style in 80% of Cor-

bicula examined on 22 February, when the pond

TABLE 2. Summary 0/ Corbicula growth and related parameters.

(P) is an abbreviation for probability and numbers in parenthesis are standard deviations.

1(1 THK NAUTILUS

JanuaiT :¥), 198n

.91(11

was ice-covered and water temperature 4.2° C, in-

dicates clams were still ingesting. According to

Pennak (1978) the crystalline style is present on-

ly in actively feeding clams and disappears when

ingestion is not occurring. Growth of Corhicula in

winter was also observed by Sickel (1976), but at

greatly reduced rates. However, Gale and Lowe

(1971) found Sphaerium transversum to cease in-

gestion at 2-4°C and Mackie and Quadri (1978)

observed no growth in Musculium secum at

temperatures less than 10° C.

Corbiciila growth during summer and fall was

similar, although water temperatures averaged

24.7° C and 11.2° C, respectively (Table 2). Similar

findings were reported by Gale and Lowe (1971)

working with S. transversum. They observed max-

imal ingestion to occur in spring, early summer,

and fall. O'Kane (1976) found Corbicula to grow

best at temperatures in excess of 24.0° C and

reported length increases averaging approximate-

ly 4.4 X 10"' mm/day. However, Corbicula

respiration has been observed to decrease rapidly

at temperatures in excess of 30° C, McMahon and

Aldridge (1976). Sickel (1976), employing frequen-

cy distribution techniques, found length increase

in Corbicula ranging from 7.2 X 10"' mm/day to

negative growth. The limited growth data avail-

able from literature is quite similar to the values

we observed for Corbicula.

Absolute growth for Corbicula in summer was

directly related to clam size. Clams 4.0 g and

larger gained significantly (P = 0.006) more

weight per day than smaller clams. In fall and

winter absolute weight gain per day of large and

small clams was not significantly different (P =

0.73 and P = 0.46, respectively). Relative growth

for Corbicula during all seasons was inversely

related to size. Smaller clams gained a signifi-

cantly (P > 0.01) greater percentage of body

weight per day than did larger clams.

ACKNOWLEDGMENTS

We would like to acknowledge assistance pro-

vided for this investigation by the Cooperative

Fisheries Research Laboratory at Southern Il-

linois University— Carbondale and Sigma Xi, the

Scientific Research Society.

LITERATURE CITED

Bickel. D. 1966. Ex»logy of Corbicula mcmilensis Philippi in

the Ohio River at Louisville, Kentucky. St erhiana 23:19-24.

Gale. W. F. and R. L. Lowe. 1971. Ph>toplankton ingestion by

the fingernail clam. Sphaerium transversum (Say), in Pool

19, Mississippi River. &ft^(9i/52(3):507-13.

Gardner, J. A., Jr., W. R. Woodall, Jr., A. A. Staats, Jr., and

J. F. Napoli. 1976. The invasion of the Asiatic clam (Cor-

bicula manile-nsis Philippi) in the Altamaha River. Georgia.

neNaufilus90(3):W.

Heinhson, G. E. 1958. Life History and Ecology of the

Freshwater Clam, Corbicula Jluminea. MA. Thesis. Univ.

Calif Santa Barbara. 64 p.

Maci<ie. G. L. and S. U. Quadri. 1978. Effects of substratum on

growth and reproduction of Mtisctdium securis (Bivalvia:

Sphaeriidae). The Nautilus 92{'iyAK-M.

McMahon, R. F. and D. W. Aldridge. 1976. Respiratory

response to temperature and low ox>'gen tensions in Cor-

bicula maniknsis Philippi. Abstract in Corbicula Newslet-

ter 1(4):6.

O'Kane, K. D. 1976. A population study of the exotic bivalve,

Corbicula manileiisis (Philippi, 1841) in selected Texas

Reservoirs. A/.S TheMs. Texas Christian Univ. 134 p.

Pennak. R. W. 1978, Freshwater Invertebrates of the United

States. John Wiley and Sons. New York. 803 p.

Rinne, J. N. 1974. The introduced Asiatic clam Corbicula, in

central Arizona reservoirs. The Nautilus 88(2):56-61.

Sickel, J. B. 1976. An ecological study of the Asiatic clam Gir-

bicula manilensis (Philippi, 1841) in the Altamaha River,

Georgia, with emphasis on population dynamics, productivi-

ty, and control methods. PhD. Thesis. Eimory Univ. 126 p.

Sinclair. R. M. and B. G. Isom. 196.3. Further studies on the

introduced Asiatic clam (Corbicula) in Tennessee. Tennessee

Dept. Pub. Health. Tennessee Stream Polution Control

Board. 78 p.

Vollenweider. R. A. 1969. A Manual for Measuring Primary

Produetion in Aquatic Environments. IBP Handbook No. 12.

Blackwell Scientific Publications. Oxford and Edinburgh.

213 p.

DEATHS

John Marwick, New Zealand paleontologists,

died at Hawkes Bay, New Zealand, on August 16,

1978, at the age of 87. He emigrated from

Scotland in the 1880's and became noted for his

work on Tertiary mollusks. An excellent

biography of him was published in Nat)trr. vol.

276, p. 428, Nov. 1978.

Mina May Slinn, amateur conchologist of St.

Petersburg, Florida, died July 29, 1979, at the age

of 69. She was an active collector and writer on

shells for .several Florida shell clubs.

Vol. 91(1)

January 30, 1980

THE NAUTILUS 11

CADULUS TETRASCHISTUS (WATSON), AN EARLIER NAME FOR

C. QUADRIDENTATUS (DALL) AND C. INCISUS BUSH (SCAPHOPODA)

Victor Scarabino

Institutx) de Investigaciones Biologicas

"Clemente Estable"

Avenida Italia 3318 - Montevideo, Uruguay

ABSTRACT

Cadulus quadridentatus (Dall, 1881) and Cadulus incisus B^ish, 1885 are junior

subjective si/nonifms o/ Cadulus tetraschistus (Watson, 1879), based on an examina-

tion of typological and other specimens. The range of this taxon is frorn North

Carolina and Bermuda, to Argentina, as far south as the GidfofSan Matias. Com-

parisons are made mth Cadulus tetrodon Pilsbry and Sharp, 1897, which is con-

sidered to be a valid species.

Siphodentalium tetraschistum Watson (1879:

521) was based on an empty shell dredged by the

"Challenger" Expedition, Station 113A, off Fer-

nando de Noronha Island (Brazil), between 7 and

25 fathoms (13 and 46 meters). A detailed

description was provided, but the illustrations ap-

peared later (Watson, 1886:pl. 2, Fig. 8a-d). Wat-

son (1885:16) compared his taxon with Siphoden-

talium bifissiim Wood, S. lofotense Sars, and S

intreum Sars.

Siphonodentalium quadridentatum was

described by Dall (1881:36) from a lot dredged off

the west coast of Florida in 30 fathoms (55

meters). He considered this nominal species to be

closely related to Watson's taxon, mentioning

that the description agreed almost exactly with

the Floridian specimens. Later Dall (1889a :428)

cited specimens as Cadulus quajdridentatus from

". . . Fernando de Noronha, 7-25 fms.," without

an explanation. The same year, Dall (1889b:295)

extended the range south to the mouth of the Rio

de la Plata ("Albatross" Station 2765).

The status of these nominal species became

confused further when Pilsbry and Sharp (1897:

148) treated Dall's species, together with CculnUis

incisus Bush, 1885, as varieties of C. tetraschistus

Watson, proposing Bush's species as intermediate

in form between the extremes represented by the

other two taxa. The confusion was compounded

when Henderson (1920:97-101) separated tetra-

schistus and quadridentatus, and further sep-

arated the latter into two subspecies, the nomi-

nate and C. quadridentatus acompsus Henderson.

In 1938 and 1942 respectively, Carcelles, and

Carcelles and Parodiz identified Cadidus tetrodon

Pilsbry and Sharp, 1897, from stomachs of star-

fish taken off Puerto Quequen (Buenos Aires,

Argentina). These specimens {ex Museo Argentino

de Ciencias Naturales, MACN 23156) and de-

posited in the Museum of Comparative Zoology

(MCZ 118674) are now labeled as Cadulus

tetraschistus. Turner (1955:314) identified (to-

gether with Carcelles' specimens) a lot taken in 7

fathoms in the Rio de la Plata by the "Hassler"

Expedition, as C. tetraschistus. She recognized

Watson's species as inhabiting southwestern At-

lantic waters, ranging from Fernando de

Noronha to Uruguay, and she considered Cadulus

quadridentatus to occupy areas from the Carib-

bean Sea to North Carolina and Bermuda, a view

held by Penna-Neme (1974:114-117). Scarabino

(1970; 1973) and Rios (1970) cited the range of C.

quadridentatus from North Carolina to northern

Argentina in depths to 42 meters, and limited C.

tetraschistus to Fernando de Noronha.

While checking the collections of several South

and North American Institutions, we e.xamined a

large series of specimens assigned to these

nominal species and compared them with the per-

tinent type material. When the type specimens of

Cadulus quadridentatus (MCZ 7739) and Cadulus

tetraschvitus (BM/NH 1887.2.9.66) were compared

we did not find enough differences to consider

them as separable species. Watson's type (Fig. la)

is a relatively immature example in a very satis-

factory state of preservation, while Dall's (Fig.

12 THE NAUTILUS

Januan- 30, 1980

Vol. 94(1)

FIG. 1. Cadulus tetraschistus (Watson, 1879) camera lucida

dramngs. a, Tiff* o/C. tetraschistus (BM/NH 1887.2.9.66). b.

Type of C. quadridenUtus (Doll 1881) (MCZ 7739) Scales in

millimeters.

lb) is a little larger and has lost the dorsal lobe.

We must conclude that Cadulus quadridentatus

and Cadulus incis-us Dall (holotype in USNM

44860) are conspecific with C. tetraschistus, the

latter name having priority.

The "remote longitudinal texture . . ." men-

tioned by Watson (1879:521) which was the only

feature that kept us from uniting these species,

was found not to be an external feature and to be

probably due to internal irregularities formed

during the construction of the shell or perhaps

due to the process of drying after coming from

the ocean. This characteristic feature is very

often observed in specimens of this and other

species of the family.

At the Academy of Natural Sciences of Phil-

adelphia, we examined three lots (ANSP 35574,

35575, and 75744) formerly labeled as tetra-

schist'us, but the labels had been changed to read

"quadridentatus ".

Syntypes of Cadulus tetrodon Pilsbry and

Sharp in the Academy of Natural Sciences

(ANSP 71070) have characteristics that caused us

to believe it to be a distinct species.

The known distribution of C. tetraschistus is

from North Carolina, Bermuda, the Caribbean

Sea, F'ernando de Noronha (Brazil), Uruguay and

Argentina as far as the Gulf of San Matias (42° S.

Lat.), with a bathymetrical range of three to 120

meters, on largely sandy substrates (Scarabino,

1975:182). Caduhut tetraschistus is reported from

the Upper Miocene and Pliocene of Florida and

Venezuela (Weisbord, 1964:134).

ACKNOWLEDGMENTS

I am indebted to the following persons for

their assistance, hospitality and the use of the

facilities of their institutions' collections which

made possible this contribution: Lie. Miguel A.

Klappenbach (Museo Nacional de Historia Nat-

ural Montevideo); Prof. Helena Martinez-Fontes

(MACN); Dr. Peter B. Mordan (BM/NH); Dra.

Licia Penna-Neme (Museo de Zoologia da Univer-

sidade de Sao Paulo); Dr. Elizer de Carvalho Rios

(Museu Oceanografico de Rio Grande); Dr. Robert

Robertson (ANSP); Dr. Joseph Rosewater

(USNM); Dr. Ruth D. Turner (MCZ). I especially

thank Dr. William K. Einerson and William Old,

Jr. (AMNH) and Dr. R. Tucker Abbott of Mel-

bourne, Florida, for their help and critical ex-

amination of the manuscript. This paper is part

of the results of the Grant 73-186A of the Inter-

national Committee for Exchange of Persons

(Fulbright-Hays Program) made to the author.

LITERATURE CITED

Bush, Katherine J. 1885. Additions to the shallow-water

Mollusca of Cape Hatteras. N.C. dredged by the U.S. Fish

Commision steamer "Albatross" in 1883 and 1884. Tmns.

Conn. Acad. Arts&Sci. 6(11): 453-180.

Carcelles. Alberto. 1944. Nuevos datos sobre el contenido

estomacal de Astropecten cingulatus Sladen. Physis

19:461-472,

and Juan Jose' Parodiz. 1938. Moluscos del con-

tenido estomacal de Astropecten cingulatus Sladen. Physis

12:252-265.

Dall, William Healey. 1881. Reports . . . steamer "Blake" . . .

15. Preliminary report on the mollusca. Bull. Mus. Comp.

Zool. 9(2):34-35.

1889a. Reports . . . steamer "Blake" 29. Report on

the mollusca. 2. Gastropoda and Scaphoptxia. Bull. Mux.

Comp. Zool. 18:418-433.

1889b. Preliminary reports . . . "Albatross" 7.

Proc. U.S. Nat. Mtts. 13(733):219-362.

Henderson, John B. 1920. A monograph of the east American

Scaphopod mollusks. Bull. U.S. Nat. Mus. 111:1-151.

Penna-Neme, Licia. 1974. Consiceracoes sobre os scaphopoda

(Mollusca) da costa brasileira, com descricao de uma nove

especie. Pap. A v. Zooi Sao Paulo 28(6): 105- 126,

Pilsbry, Henr>' A. and B. Sharp. 1897. Scaphopoda. Mariual of

Corwhology. (Ser. 1)17:1-280.

Vol. 94(1)

January 30, 1980

THE NAUTILUS 13

Rios, Elizer de Carvalho. 1970. Coastiil Brazilian S<'(Uihellx.

Fund. Univ. R.G. Mus. Oceanogr. R.G.S. Brasil, 255 pp.

Scarabino. Victor. 1970. Las especies del genero ('(ululus

Philippi, 1884 (Moll. Scaphopoda) en el Atlantico sudoc-

cidental (lat. 24° S a 38° S). Com. Soc. Malar. Urug.

3(19):39-48.

1973. Scaphopoda (Moll.) del sur del Brasil

Uruguay y Argentina hasta 42' S.- (Sistematica, Distribu-

cion) Trah. V. Cimgr. Latinoam. Zool. 1:192-203.

1975. Class Scaphopoda: 180- 186 /in/ Rios, Elizer

de Carvalho — Brazilian Marine Mollusks Iconography.

Fund. Univ. R.S. Mus. Oceanogr. R.G.S. Brasil.

Turner, Ruth D. 1955. Scaphopods of the Atlantis dredgings in

the Western Atlantic, with a catalogue of the scaphopod

types in the Museum of Comparative Zoology. Pap. Mar.

Biol. Oceanogr.: .309-320. Pergamon Press Ltd.

Watson. Robert B<x)g. 1879. Mollusca of the "Challenger" ex-

pedition 2. The solenoconchia, comprising the genus Den-

talium. Siphodentalium and Caduius. Jtmr. Linn. Soc. Lon-

don 14:.506-529.

1885. Report on the scaphopoda and gasteropoda

collected by H.M.S. Challenger during the years 1873-76.

Reptii. Sci. Res. Challenger Zool. 15:1-24, (pis. l-III, 1886).

Weisbord, Norman E. 1964. Late Cenozoic scaphopods and ser-

pulid Polychaetes from Northern Venezuela. Bull. Amer.

Paleo 47(214):111-141.

MUSSELS OF FLOYD'S FORK, A SMALL NORTHCENTRAL

KENTUCKY STREAM (UNIONIDAE)

Ralph W. Taylor

Dept. of Biological Sciences

Marshall University

Huntington, W. Va. 25701

ABSTRACT

A survey of the mussels of Floyd's Fork, a small northcentral Kentucky

tribiitary of the Salt River, was carried out during the summer of 1978. Six sta-

tions were collected in Floyd's Fork unth a seventh station being located on Salt

River near the confluence of the two streams. T\oenty-five species were collected.

Of these Quadrula nodulata, Lampsilis teres, and Corbicula leana are reported for

the first time as occurring in the Salt River drainage. Floyd's Fork appears to be a

stream of high water quality which supports a healthy, rather abundant, highly

diversified mussel fauna.

A number of surveys of the naiad faunas of

major streams in Kentucky have been effected

over the last fifty years. Ortmann (1926),

Stansbei-y (1965, 1969), Clench and van der

Schalie (1944), Isom (1969), Blankenship and

Crockett (1972) and Williams (1969) have looked

at such streams as the Ohio, Cumberland, Ten-

nessee, Green, Kentucky and Rockcastle Rivers.

Stansbery (1978) is at the present time working

on the Licking River in eastern Kentucky.

There is, however, a dearth of papers dealing

with faunas of smaller streams. Stansbery (1978)

implies that in this time of rapid extinction of

aquatic organisms, as a result of habitat destruc-

tion or modification, many species have been ex-

tirpated from the main waterways and may exist

only in isolated refugia well up into the head-

waters of smaller streams. These smaller tribu-

taries most often do not suffer from pollution

(urban sewage, industrial, mining, etc.) to as

great a degree as do larger streams.

This paper reports on work carried out in such

a stream, Floyd's Fork, located in northcentral

Kentucky. Floyd's Fork originates in north-

eastern Oldham County near the village of

Ballardsville and meanders for nearly 80 km

across the county, through adjacent Jefferson

County, and terminates in Bullitt County at its

confluence with the Salt River. Salt River is a

fairly large tributary of the Ohio River and joins

14 THE NAUTILUS

January 30. 1 980

Vol, 94(1)

with the Ohio approximately 30 km downstream

of Louisville, Ky. within the boundaries of the

Fort Knox Military Reservation (see map of

study area).

Throughout the summer of 1978 six sites were

collected along Floyd's Fork. In addition a

seventh site was located on Salt River just

upstream of the point of merger of Floyd's Fork

with Salt River. Clench and van der Schalie

(1944) and Rosewater (1959) have previously col-

lected in the Salt River. However their activities

were centered near Bardstovm, Nelson County,

Kentucky (approx. 50 km upstream and east of

the site reported here). I have been unable to find

an account of work having been done previously

on Floyd's Fork.

METHODS

All si)ecimens were hand-picked. Only live

specimens or fresh empty shells were retained.

Live specimens were obtained for all of the

species listed below except Lampsilis teres which

was found only as fairly old dead shells. Most of

the material collected is presently housed at Mar-

shall University with a series of voucher speci-

mens also having been deposited with the Ohio

State Museum of Zoology (OSUM #42269-42310).

Collecting stations

1. Floyd's Fork Creek at Aiken Rd. Bridge.

Aiken Rd. exits U. S. Highway 60 approxi-

mately 3 km E. of Middletown, Ky. (Jefferson

Co.)

2. Floyd's Fork Creek at Beckley Station Rd.

Beckley Sta. Rd. exits U.S. Highway 60 approx.

6 km East of Middletown and intersects Coun-

ty Rd. 1531 after fording Floyd's Fork. (Jeffer-

son Co.)

3. Floyd's Fork Creek at State Rd. 155 bridge, 1.5

km E. of Fisherville, Ky. (Jefferson Co.)

4. Floyd's Fork at County Rd. 1531 bridge, 300 m

South of intersection with State Rd. 155, 3 km

West of Fisherville. Ky. (Jefferson Co.)

5. Floyd's Fork at U.S." Highway 31-E bridge. 1

km North of Bullitt Co. line. (Jefferson Co.)

TABLE 1. List of species collected from Floyd's Fork Creek

and Salt River. Relative abundance indicated as follows: (C

= common, M = modenUely common. R = rare).

species najDc

Site Number

12 3 4 5 6 7

Fusconaia flava (Raf.)

Megalonaiag nervosa (Raf.)

Amblema plicata (Say)

Quadrula pustulosa (Lea)

Quadrula nodulata (Raf.)

Quailru)B quadrula (Raf.)

Tritugonia verrucosa (Raf.)

Pteurobeoa clava (Laa.)

Elliptio dilatatus Raf.

LasBigona costata (Raf.)

LasBigona complanata (Barnes)

Anodonta lobccillis (Say)

Anodonta grandis Say

A)asBidonta viridis

Stropliitua undu>atus (Say)

Ptychobranchus fasciolaria (Raf.)

Obliquaria reflexa Raf.

Truncilla truncata (Raf.)

Leptodea fragilis (Raf.)

Potaailua alatus (Say)

Toxolasna parvus (Barnes)

LaaipsDia ter«a (Raf.)

LaapBi)is r. luteola (Laa.)

lanpsilia ventricosa (Bamea)

Corbicula leana Prine

X X X X X

X X

X X X X X X

X X X X X X

X X X X X

X X

X X X X X X

XXX

X X

X

X X X X X X X

XX X X X X

Vol. 91(1)

January 30, 1980

THE NAUTILUS

6. Floyd's Fork at bridge on Seatonville Rd.

(County Rd. 1819) 1.6 km West of the village

of Seatonville. (Jefferson Co.)

7. Salt River, Off County Rd. KMiO at a)ntluence

of Goose Creek with Salt River. 3 km S.W. of

the village of Waterford, Ky. (Spencer Co.)

RESULTS AND REMARKS

A total of twenty-five species were collected

during this study. Of this number five species

(Megalonaias nervosa, Quadrula nodulata.

Quadrula quadrula. Obliquaria reJJexa. and

Lampsilis teres) were found only in the Salt

River. Quadrula nodulata^ Lampsilis teres, and

Corhicula leana [also called manilensis and

Jluminea — editor] are reported here for the first

time as occurring in the Salt River drainage.

The presence of Corbicula far upstream in

Floyd's Fork (Sta. #3) is another indication of

just how cosmopolitan this introduced Asian

species has become. Sinclair and Isom (1961)

reported the presence of Corbicula in the Ohio

River (for the first time) based on specimens col-

lected near Paducah, Ky. in 1957. Other authors

place the time of arrival of Corbicula in the area

of the confluence of Salt River with the Ohio at

around 1963. If one assumes a route of dispersal

from the Ohio River, to Salt River, to Floyd's

Fork Station #3, one must assume a fairly

remarkable rate of range expansion equal to 100

km/15 year period of time or approx. 6.6 km/

year.

The overall number of species, and large

numbers of individuals of each species present.

indicates a stream of rather high water quality

and a bivalve population that is both stable and

healthy.

ACKNOWLEDGMENTS

I wish to thank Dr. David H. Stansbery of the

Ohio State University Museum for confirming

identifications for me.

LITERATURE CITED

Blankenship, Shaw, and D. R. Crockett. 1972. Changes in the

Freshwater Mussel Fauna of the Rockcastle River at Liv-

ingston, Kentucky. Trans. Ky. Acad. Sri. 33:.37-39.

Clench. Wm. and Henry van der Schalie. 1944. Notes on

Naiades from Green, Salt, and Tradewater Rivers in Ken-

tucky. Mich. Acad. Set. 29:223-229.

Isom, Billy G. 1969. The Mussel Resource of the Tennesse

River. Malacologia 7(2-3):397-425.

Ortmann. A. E. 1926. The Naiades of the Green River

Drainage in Kentucky. /Iren. Carnegie Mas. 17:167-188.

Rosewater. .Joseph. 19-59. Mollusks of the Salt River Kentucky.

ne Nautilm 73(2):57-63.

Sinclair. R. M. and Isom, B. G. 1961. A Preliminary Report on

the Introduced Asiatic Clam Corbicula in Tennessee.

Stream Poll. Bd. Tenn. Dept. of Pub. Health. 31 pp.

Stansbery, David H. 1965. The Naiad Fauna of the Green

River at Munfordville, Kentucky. Annual Reports for 1965

oftheAmer. Mai Union, pp. 13-14.

1969. Changes in the Naiad Fauna of the

Cumberland River at Cumberland Falls in Eastern Ken-

tucky. Ann. Reports for 1969 of the Amer. Mai. Union, pp.

16-17.

1978. Personal Communication at the Ohio State

Museum of Zoology.

Williams, John C. 1969. Mussel Fishery investigation Ten-

nessee. Ohio and Green Rivers Final Report. Ky. Dept. of

Fish and Wildlife Resources. 106 pp.

Specimen Shells

Offering microscopic and mmiature (to ': inch) shells from

the Florida Keys, with accurate locality data. Also unsorted

grunge: write for list.

Margaret Teskey

P. 0. Box 27.1

Big Pine Key. Fl. ^mi-l

■W^P-l

»<»»^^^^^l

Rare and Exotic Specimen Shells

for the discriminating collector

Free price list

Janowsky's

MAL DE MER ENTERPRISES

946 Ralph Avenue

Brooklyn, New York 11236 USA

(212) iS5-S550

16 THE NAUTILUS

January :iU, 198U

Vol. 94(1)

A NEW FOSSIL RADIOCENTRUM (PULMONATA: OREOHELICIDAE)

FROM NORTHERN COAHUILA, MEXICO

Artie L. Metcaif

Department of Biological Sciences

University of Texas at El Paso

El Paso, Texas 79968

ABSTRACT

A new species of oreohelwid land snail, Radiocentrum orientalis, is described

from the Serranias del Burro, a mountain range of northern Coahuila, Mexico.

Specimens are fossils from probable Pleistocene deposits. This is the easternmost

record of the genus. Distribution of the genus in Mexico is discussed.

Recognition of the taxon Radiocentrum as a

separate genus in the family Oreohelicidae was

recommended by Babrakzai, Miller and Ward

(1975) and was followed by Christensen and

Miller (1976). Formerly Radiocentrum had been

considered a subgenus of Oreohelix.

The present species is described from fossil

shells, probably of Pleistocene age (judging by the

massive canyon fill in which they occur and the

nature of the associated molluscan fauna). Speci-

mens were collected on an expedition arranged

by Mr. David H. Riskind, Texas Parks and Wild-

life Department, and Mr. Robert Burleson, Tem-

ple, Texas, to whom I am indebted.

Radiocentrum orientalis n. sp.

(Kigs. 1-3)

Diagnosis: Although poorly preserved,

specimens of this species exhibit (1) the riblets

(Fig. 3) that are characteristic of the embryonic

whorls of Radiocentrum and (2) the narrower,

more deeply impressed early whorls (Fig. 2) of

that genus as contrasted with Oreohelix. It differs

from most species of Radiocentmm in possessing

an elevated spire, a characteristic found,

elsewhere, only in species of the Chiricahua

Mountains, Arizona. However, kinds described

from the Chiricahua Mountains are variously

wider, thinner-shelled, more carinate or bear

spiral striae, in contrast to the species described

here.

Description of Holotype: Fossil shell, heavy

(thick-walled), 11.8 mm in diameter and 7.9 mm

high, elevated, with spire forming angle of 123°,

spire protrusion 2.1 mm: body whorl with upper

lip of aperture descending to immediately below

angularity; aperture subrounded, 4.7 mm wide

and 4.5 mm high (excluding walls), aperture

oriented obliquely at angle of 35° to vertical; um-

bilicus narrow, 1.7 mm wide, slightly overlapped

by lower lip, contained 6.9 times in shell

diameter; tightly coiled with 5.5 whorls; sutures

of early whorls deeply impressed; shell surface

has suffered loss of periostracum; radial ribs ap-

pear dimly on last 1/4 of embrj'onic whorl and

continue to 1.7 whorls; thereafter appear growth

wrinkles, these becoming increasingly coarser and

more irregular in occurrence on body whorl, dor-

sally; ventral surface of body whorl smoother

with a few low growth wrinkles; shell bleached,

mainly white except for some tannish color on

whorls 1.5 to 3 (no evidence of color bands).

FIGS. 1-3. Radiocentrum orientalis new species. 1 and 2,

ApertumI mtd dorsal ricics af haloti/pe (ll.fl mm, diameter;

USNM 7.'if<S20): 3, Apical whorh of a paralype (scanning elec-

tron micrograph, courtesy of I >r. W. R. Roser).

Vol. 91(1)

Januaiy 30, 1980

THE NAUTILUS 17

Pamt ifpes: Only eight paratypes were secured,

all smaller than the holotype and some damaged

by breakage. On some of these smaller shells the

riblets of the embryonic whorls, typical of the

genus, are better preserved (Fig. 3).

Etymology: L. oyientaiis. of the east, in

reference to the occurrence of this species farther

east than other known members of the genus

Radiocentmm.

Disposition of Types: Holotype, USNM 758820.

Paratypes: University of Arizona 6258; Universi-

ty of Texas at El Paso 5647, 5660.

Type Locality: MEXICO, Coahuila, Mcpo. de

Villa Acuna, Serranias del Burro, 29''00'30"N;

102°05'55"W. Upf)er end of Canon el Bonito at ca.

1680 m; 200 m up-canyon from a concrete stock

tank (pila): from sediments exposed on west wall

of canyon, 5-10 m above canyon floor. These

sediments underlie a fan of mixed alluvium and

colluvium, which has been dissected by the arroyo

in the floor of the canyon. A single shell was

found in sediments approximately 1.5 km up-

canyon, northward, from the type locality.

Associated Fauna: Fossils associated with R.

orientaUs at the two localities noted above were

the following (asterisk indicates species not found

living in the area): 'Cochlicopa lubrica (Miiller),

'Pupilla blandii Morse, 'Vallonia gracilicvsta

Reinhardt, a succineid, sp. indet., 'Rahdotus

dealbatus (Say), 'Disc^is cronkhitei (Newcomb),

Helicodiscus eigenmanni Pilsbry, Retinella

(Glyphyalinia) indentata paiicilirata (Morelet)

and Zonitoides arboreus (Say). The high propor-

tion of species not found at present in this and

nearby canyons suggests a markedly different

paleoenvironment. It seems likely that these

snails lived during a glacial age of the

Pleistocene. The present fauna has a marked af-

finity to that of the Sierra Madre Oriental of

Mexico, to the southeast, in contrast to the fossil

assemblage.

DISCUSSION

Reports of oreohelicids from Mexico have all

appertained to the genus Radiocentrum. These

records are exceptionally widely scattered. Two

species have been described from Baja California

Sur (Miller, 1973; Christensen and Miller, 1976),

two species from northwestern Chihuahua (Pils-

bry, 1948) and one species from southeastern

Chihuahua (Drake, 1949). The Serranias del

Burro of Coahuila are some 1000 km distant from

Baja California Sur and 380 km from the type

locality of R. almoloya (Drake), 1949, near

Salaices, Chihuahua. It is likely that lack of col-

lecting in the mountains of northern Mexico,

especially of Pleistocene fossil gastropods, may

account for this scattered distributional pattern.

It is also possible that this is a venerable genus

in Mexico and one in which rifting in the Gulf of

California and uplift of the Sierra Madre Oc-

cidental (and other ranges) may relate to disjunc-

tions in distribution.

Shells of R. almoloya, like those of R. orien-

talis. appear to me to be fossil. Possibly the genus

Radiocentrum may no longer exist in the former,

eastern part of its range. There seems a general

pattern of extirpation of oreohelicid snails in the

southeastern part of the range of the family.

Thus, fossil shells, only, are knovra from the

Sierra Rica, Tres Hermanas, Florida, Cooke,

Caballo and San Andres Mountains of southern

New Mexico and from the Franklin, Hueco and

Guadalupe Mountains of Texas. The Sacramento

Mountains of New Mexico are rich in fossil

oreohelicids but the only living species there,

Oreohelix strigosa nogalensds Pilsbry, 1939, is of

restricted occurrence. All this suggests inability

of these southeastern oreohelicids to adjust to

regional climatic changes.

LITERATURE CITED

Babrakzai, N., W. B. Miller and 0. G. Ward. 197.5. Cytotax-

onomy of some Arizona Oreohelicidae (Gastropoda: Pul-

monata). Bull Amer. Malaail. Union 40:4-11.

Christensen, C. C. and W. B. Miller. 1976. A new Radiucen-

trum (Pulmonata: Oreohelicidae) from Baja California,

Mexico. The Fe/iyer 18:378-380.

Drake, R. J. 1949. A new species of Oreohelix. subgenus

Radiocentrum. from southeastern Chihuahua. The Nautilus

62:109-112.

Miller. W. B. 1973. A Recent Oreohelix (Gastropoda:

Pulmonata) from Baja California Sur. Mexico. The Veliger

15:.332-:334.

Pilsbry, H. A. 1948. Inland mollusks of northern Mexico.— I.

The genera Humboldtiana, Sonorella. Oreohelix and

Afihmunella. Proc. Acad. Natur. Sci. Philadelphia

100:18.5-203.

18 THE NAITILUS

Januan- :30. 1980

Vol. 94(1)

OBSERVATIONS ON THE TERRESTRIAL GASTROPODS IN THE VICINITY OF

JASPER, ALBERTA (CANADA)

Thomas R. Piatt '

Department of Zoology

University of Alberta

Edmonton, Alberta, T6G 2E9 Canada

ABSTRACT

Fourteen apecies of terrestrial gastropixh were collected in the mcinity of

Jasper, Alberta, from April through September. 1976: Zonitoides nitidus, Retinelia

electrina, Striatura ferrea and Pupisoma sp. are new locality records for the prov-

ince of Alberta.

There are few published records of terrestrial

molluscs in Alberta. The majority of these reports

(Taylor. 1895; Berry, 1922 and Mozley, 1926, 1931)

deal with the mollusc fauna of the Rocky Moun-

tain regions of the province. There are no recent

reports, to my knowledge, of terrestrial gastro-

pods from Alberta.

An intensive investigation designed to identify

the molluscan intermediate host(s) of Parelaph-

ostrongylus odocoilei (Nematoda: Metastrongy-

loidea), a parasite of mule deer (Odocoileus he-

mioniis hemioniLs), resulted in the collection and

identification of approximately 8,500 terrestrial

gastropods in the general vicinity of Jasper,

Alberta (Piatt, 1978). The majority of the

molluscs reported herein have been recorded in

previous investigations of the mollusc fauna of

the Rocky Mountains in Alberta. Several

gastropods found during the present study have

not previously been reported from Jasper.

METHODS

Molluscs were collected weekly from 23 April

to 24 August 1976, with the exception of the third

week in May and the second week in July. Two

additional collections were made on 7-8 and

21-22 September. Mollusc identifications were

made with the aid of Burch (1962) and Pilsbry

(1946, 1948). All collections were done by hand. A

variety of natural material (logs, rocks and leaf

litter) was examined for gastropods as well as

man-made debris.

' Now in the Department of Biology, University of Richmond,

Richmond. VA 23173.

STUDY AREAS

Jasper, Alberta (53°32'N, 113°36'W) is approx-

imately 400 km west of Edmonton, in the eastern

foothills of the Rocky Mountains. The townsite

(Fig. 1) is situated in the center of Jasper Na-

tional Park. Five collecting sites, all located

within 5 km of the townsite, were selected on the

basis of major vegetation types. Elevation of the

sites ranged from 1120 m (Areas I and H) on the

floor of the Athabasca Valley to 1500 m at area

V(Fig.l).

Area I (Fig. 1) is an open, grassy area adjacent

to the Highway 16 by-pass, east of the townsite.

This area was disturbed by the construction of

the highway and contains a number of large

rocks that are potential mollusc refuge sites.

Native and introduced grasses are the predomi-

nant vegetation. A few juniper (Junipenis sp.)

and bearberry (Arctostaphylos uva-ursi) are pres-

ent, as well as lodgepole pine seedlings (Pimis

contorta).

Area II is a canopied region adjacent to Area I,

bordered on the east by the Athabasca River

(Fig. 1). The predominant vegetation is lodgepole

pine, interspersed with aspen (Populus

tremuloides). The predominant shrubs are

juniper, bearberry, and buffaloberry (Shephcrdia

canadensis). There is a large variety of material

(man made) for refuge sites, as well as an abun-

dance of natural material (aspen and lodgepole

pine logs).

Area III is a transition area between valley

and mountainous habitat, directly west of the

tovrasite (Fig. 1). There is a sharp transition and

Vol. 94(1)

.Ianuarv:?n, 1980

THE NAUTILUS 19

CN TRACKS

HIGHWAY 16-0- )J

PATRICIA I 1j

LAKE I A

AREA V^^f

,0/0

* AREA III

O JASPER ^^J

* TOWNSITI

FIG. 1. Diagrammatk representation of the Jasper Toumsite

(Jasper, Alberta), indicating the areas of mollusc collection.

a dramatic increase in elevation. The predomi-

nant vegetation is grass and an occasional

lodgepole pine. Buffaloberry, bearberry and

junif)er are common.

Area IV is situated northwest of the tovrasite

(Fig. 1). It is a marshy zone with sedge (Carex

sp.) as the predominant vegetation.

Area V consisted of two disjunct stands of

aspen, surrounded by and interspersed with

lodgepole pine. These sites are located north and

south of Area IV (Fig. 1). Bearberry, buffaloberry

and juniper are the most common shrubs.

MOLLUSCS

A summary of all molluscs collected, the area

of collection and previous reports in Alberta is

given in Table \.

Limacidae

Deroceras laeve (Miiller) has previously been

reported from Alberta as Ldmax hyperboreas by

Taylor (1895) and Agriolimax hyperboreas by

Mozley (1931). Pilsbry (1948) clearly regards A.

hyperboreas as a synonym of D. laeve.

Deroceras laeve, the only slug encountered, was

found in all areas examined. Individuals of this

species were most commonly encountered in the

open, grassy Area I, under rocks and, occasional-

ly, other material. Deroceras was also common in

Areas II and III, but scarce in Areas IV and V.

All the slugs collected were measured, while

alive and in an extended position, to the nearest

0.1 mm with precision calipers. The mean length

of D. laeve declined from 15.9 mm in April to

late June to 12.3 mm in late July (Fig. 2) (t =

4.112; t~ 0.001 = 3.291; P< O.(XJl) indicating a

change in the population structure at this time

and a single generation per year for D. laeve in

the Jasper area.

TABLE 1. Species and locatum of terrestrial gastropods co-

llected in Jasper, Alberta (1976) ivith premovs reports of

these species in Alberta

* see text for a description of the study areas.

" 1-Taylor (1893) Laggan (= Lake Louise); 2-Taylor (1895),

a-35 miles east of Red Deer. b-MacLeod, c-Olds: 3-Berry

(1922), a-Kanaskis, b-Morley, c-Waterton Lake. d-Bow River;

4-Mozley (1926) Jasper National Park; .'vMozley (1931) Jas-

per National Park.

20 THE NAUTILUS

Januar\'30, 1980

Vol. 94(1)

20

E

1 15

UJ

N

'■

10

A M J J A S

COLLECTION PERIODS (197^

FIG. 2. Mean lengths of Deroceras laeve collected in Jasper.

Alberta. Bar represents one standard deriation.

Zonitidae

Euconulus falvus (Miiller) was the most com-

monly encountered mollusc during this study.

This species was found in all areas, with the ex-

ception of Area IV. Euconulus was the most

abundant mollusc in Areas I and II, but was also

common in Areas III and V.

Mozley (1926, 1931) reported Euconulus cher-

sinus polygyratiis from a variety of locations in

Jasper National Park. Euconulus fulims differ

from E. chersinus, externally, in having fewer

number of whorls, 5 1/2 to 6 1/2-7 1/2 (Pilsbry

1946). All specimens collected in the present

study had 5 to 5 1/2 whorls and were un-

mistakably E. fulvus.

Zonitoides arboreus (Say) and Zonitoides

nitidus (Miiller) were collected in Areas I, II, III

and V. Zonitoides arboreus was common in Areas

I and II and more abundant than Z. nitidus in all

locales. Both species of this genus were rare in

Areas III and V.

This is the first report of Z. nitidus from

Jasper, although it is considered "commonly

distributed in the Canadian Zone" (Pilsbry, 1946).

TTiis species is widespread in the western United

States (Pilsbry, 1946).

Vitrina limpida Gould was common during the

latter half of the summer. The first individuals

were collected during 19-21 July. Prior to this

time the only evidence of Vitrina was the

presence of large numbers of shells encountered

while collecting.

Striatum ferrea Morse is a new record for

Jasper and Alberta. This species was encountered

infrequently (33 specimens) and it was restricted

to the aspen-dominated Area V.

Retinella electrina (Gould) has not previously

been reported from Alberta. Pilsbry (1946) in-

cludes Washington, British Columbia and Alaska

in the range of this species. Retinella was also

encountered infrequently (12 specimens) and was

restricted to Areas I and V.

Endodontidae

/)i.sn/,s cronkhitei (Newcomb) was present in

all areas with the exception of Area IV. This

species was commonly encountered in Areas I

and II, however, only a single specimen was

found in Area III. Discus cronkhitei replaced £!

fidvus as the most abundant mollusc in Area V.

Discus shimeki (Pilsbry) is a new record for

Jasper. This species has been reported from the

Kananaskis region (Berry, 1922). Discus

cronkhitei was encountered most frequently in

Area I, occasionally in Area II and a single

specimen was found in Area V.

Succineidae

Oxyloma retusa (Lea) was restricted to the

marsh (Area IV). This species was common and

has been reported from Jasper and other loca-

tions in Alberta (Table 1).

Pupillidae

Vertigo modesta (Say) was the most common of

the pupillids encountered during this study. It

was found in Areas I, II and V, but most com-

monly in Area II.

Verti-go ovata Say was represented by a single

specimen from Area V. Mozley (1931) reported V.

omta from very near the area examined during

the present study.

Columella edentula (Drapanaud) was repre-

sented by three specimens collected in Area II.

The range of C. edentula extends "across Canada"

(Pilsbry, 1948). Taylor (1895) listed Pnpa simplex

from Laggan Alberta ( = Lake Louise), which is

regarded as a synonym of C. endentida.

Single specimens, referred to the genus

Pttpisoma Stoliczka, were collected from Areas I

and II. The range of Pupisoma is restricted to the

Vol. 94(1)

January 30, 1980

THE NAUTILUS 21

southwestern United States (Pilsbry, 1948).

However, with the high influx of tourists into

Jasper, an accidental introduction is not unlikely.

DISCUSSION

The gastropod fauna in the areas examined is

relatively homogeneous (Table 1). Areas I, II and

V share 80% of the species that occur in any one

of those areas. Area I and II share all but two

species. Striatura ferrea, in the aspen-dominate

Area V, and Oxyloma retusa, in Area IV, are the

only specialists identified in the present study.

The pupillids. Vertigo ovata (Area V) and Col-

umella edentula (Area II) were encountered too

infrequently to be described in these terms.

Stands of coniferous forest are generally con-

sidered to be poor mollusc habitat (Walker, 1902;

van der Schalie, 1940). Recent reports (Clarke, et

al. 1968) in New Brunswick dispute these find-

ings and furnish evidence that a variety of ter-

restrial gastropods inhabit coniferous forests.

Area II in the present study is dominated by

lodgepole pine (Pinus contorta), interspersed with

aspen. Ten species of molluscs, although not as

abundant as in Area I, were collected from this

stand. It is interesting to note that, although no

quantification was attempted, the majority of

molluscs collected were found in association with

aspen or aspen logs that had fallen or been

moved into the surrounding conifers. This is cor-

roborated by a similar observation (Mozley, 1937)

for terrestrial gastropods collected in nearby

areas. Therefore, more specific mollusc-plant

associations may provide "patches" for terrestrial

molluscs.

The terrestrial gastropod fauna of Jasper is

composed of generalists that have successfully

adapted to the boreal regions (Mozley, 1937). The

majority of these species have circumboreal

distributions or have closely related sister-species

in Eurasia (Likachev and Rammel'maier, 1952).

The fauna of the towmsite of Jasper lacks several

species (6) that have been previously reported

from the Park (Mozley 1926, 1931). These include

Vallonia cdbula, Cionella (formerly Cochliopa)

lubrica, Succinea avara and two species of

Oreohelix, all of which would be expected to in-

habit areas similar to those examined in this

study.

ACKNOWLEDGMENTS

I would like to thank Parks Canada for grant-

ing permission to collect snails in Jasper Na-

tional Park. Financial support for this research

was provided by Parks Canada, Alberta Fish and

Wildlife Division and a National Research Coun-

cil Operating Grant to Dr. W. M. Samuel (No.

A6603).

LITERATURE CITED

Berry, S. S. 1922. Land snails from the Canadian Rockies.

Mux. Bull. Ottawa 36:1-19.

Clarke, A. H., J. P. Kelsall and G. R. Parker. 1968. The land

snail fauna of Fundy National Park. New Brunswick. Nat.

Mtis. Catiada, Bull. No. 223, Cent. Zool. 5-22.

Likhachev, I. M. and E. S. Rammel'maier. 1952. Terrestrial

Mollusks of the Fauna of the USSR. Izdatel. Akad. Nauk

SSSR. Moscow. 511 p. Translated by the Israel Program for

Scientific Translations. Jerusalem.

Mozley, A. 1926. Preliminary lists of the moUusca of Jasper

Park, Alberta. The Nautilus 40:53-56.

1931. Reports of the Jasper Park Lakes investiga-

tions, 1925-1926. The moUusca of Jasper Park. TVans. Royal

Soc. Edinburgh 46:647-669.

1937. A biological study of the sub-Arctic

MoUusca. Proc. Amer. Phihsoph. Soc. 78:147-189.

Pilsbry, H. A. 1946. Land MoUusca of North America (North

of Mexico). Vol. IL Part 1. Acad. Nat. Sci. Philadelphia.

Monographs. No. 3. 520 p.; 1948, ibid, Vol. IL Part 2 and 3.

pp. 521-1113.

Piatt, T. R. 1978. The life cycle and systematics of

Parelaphostrongylus odocoilei (Nematoda: Metastron-

gyloidea), a parasite of mule deer (Odocoileus hemionus he-

mionus). with special reference to the molluscan in-

termediate host. Ph. D. Thesis. Univ. of Alberta. Edmonton.

233 p.

Taylor. G. W. 1893. Land and freshwater shells in the Rocky

Mountains. The Nautilus 8:85-86.

1895. TYie land and freshwater shells of Alberta.

O^HMiaA'ar. 9:173-178.

van der Schalie. H. 1940. Larger land shells from pine woods

in northern Michigan. Pap. Mich. Acad. Sci., Arts and Let-

ters. 25:367-370.

Walker, B. 1902. Hints on collecting land and freshwater

mollusks. Jour AppL Microsc. Lab. Meth. 5:1954-1961.

22 THE NAUTILUS

January 30. 1980

Vol. 94(1)

BIVALVE MOLLUSCA OF THE YALOBUSHA RIVER, MISSISSIPPI'

Charles M. Cooper

USDA Sedimentation Laboratory

Oxford, Mississippi 38655

and

ABSTRACT

V. Wayne Johnson

Department of Biology

University of Mississippi

University, Mississippi 38677

The bivalve fauna of the Yalobiisha River in north central Mississippi was ex-

amined from 1973 to 1976. Of the 15 species found, 8 were not reported by Hinkley

in 1906, whereas we did not firui 13 of the species that he collected. There are four

different types of habitat. Carunculina parva was the main inhabitant of the up-

per portion of the river with its sandy substrate and sluggish low flow; Sphaerium

rhomboideum was the dominant Molhtsca of the reservoir; while Quadrula

pustulosa, Proptera purpurata, and Lampsilis anodontoides composed the majority

of the bivalves in the swift waters below the reservoir spillway.

The bivalve fauna occupying the various aquat-

ic habitats of the Yalobusha River in north cen-

tral Mississippi was studied from 1973 through

1976. The river was sampled by Hinkley in 1906

during a study of Mollusca in selected streams in

Mississippi and Alabama. Since that time the

river's environment has been altered extensively

from its original state of a meandering, wooded

stream by channelization, the building of a

40-km^ flood control reservoir, and changes in

land use.

Although the molluscan fauna of most of the

Mississippi River Basin has been well-docu-

mented, Hinkley's study (1906) is the only one

from the northwest Mississippi area. He listed 34

species from Floating Creek, the Yalobusha,

Tallahatchie, Big Black and Tombigbee rivers in

Mississippi. Of those species, 16 were found in the

Yalobusha River. Ortmann (1924, 1925) studied

the molluscan fauna of the Duck and Tennessee

rivers, and the mollusks of Alabama were in-

vestigated by Goodrich (1930) and van der Schalie

(1938).

The objectives of the study were not only to

determine species composition changes since land

use and channelization have occurred but also to

add to the knowledge of the taxa of Mollusca in

Mississippi.

' Contribution of the U. S. Sedimentation Laboratory,

USDA -SEA -AR, with the University of Mississippi.

Habitats

The Yalobusha River (Fig. 1) flows in an east-

west direction through the sandy-loess hills of

Mississippi cutting through Eocene and Paleocene

formations forming a broad valley. Observations

indicated that Mollusca occupied 4 major aquatic

habitats: 1) river bottom; 2) reservoir littoral; 3)

reservoir profundal, and 4) tailwaters below the

reservoir spillway.

The river bottom substrate (Station 11) was

mainly sand and gravel with a ripple-shallow

pool combination along the dredged channel.

Pools contained some clay and silt deposits.

Water depths normally ranged from 0.05-0.2 m in

ripples and 0.5 to 1.5 m in pools. Because the

river and its immediate drainage has been chan-

nelized, runoff rates have increased and the

stream was subject to flash flooding after

moderate rainfall amounts. Thus the stream was

subject to molar activity as well as scouring and

redeposition of sediments.

The littoral zone of the reservoir was subject to

water-level fluctuations, wave action and draw-

down and had a substrate varying from sand or

sandy gravel to gumbo or hardpan clay (Cooper,

1977). The profundal zone had more stable mud-

muck bottom than the littoral zone and never ex-

perienced drawdovm.

The spillway and tailwaters area below the

dam (Station 13) created an artificial habitat of

swift, turbulent waters. The channel center was a

Vol. 94(1)

Januarv '^0. 1980

THE NAUTILUS 23

CALHOUN CITY

FIG. 1. Map of iitudy porium of the Yalobusha River, including Grenada Lake. Mississippi.

sand-gravel cenosis or mud-muck bottom, and the

sides were rock boulders laid by the U. S. Corps

of Engineers to control channel erosion.

Collecting Methods

We collected in shallow river reaches by hand

sampling and by dragging the bottom substrate

with a D-frame dip net and sampled in the

deeper water by Peterson and Ekman dredge

hauls. Mollusca were taken in the swift waters

below Grenada Reservoir by dredging and by

hand sampling when spillway gates were closed.

Lake samples were quantitative and taken in

transects; however, most river sites had so few

Mollusca that quantitative sampling was impossi-

ble. Turbidity levels made SCUBA sampling im-

practical in deeper areas. Representatives of all

species of clams were verified by Dr. Henry van

der Schalie of the University of Michigan.

Voucher specimens are on file at the Department

of Biology, University of Mississippi.

RESULTS AND DISCUSSION

Representatives of 15 species of Mollusca were

TABLE 1. Taxonwnic list of Bivalvia identified during the

197S-1976 study of the Yalobusha River including Grenada

Reservoir with distribution by habitat, and those identified

byHinkky(1906).

Distribution Code: A = Yalobusha River above Grenada

Reservoir; B = Grenada Reservoir — littoral; C = Grenada

Reservoir — profunda!; D = Yalobusha River tail waters below

Grenada Dam.

24 THE NAUTILUS

Januan- 30, 1980

Vol. 94(1)

collected during the study (Table 1). Of the four

species found in the upper portion of the river

(Table 1), only Caninculina parva was found in

abundance and only Uniomerus tetralasmus was

recorded by Hinkley (1906). Carunculina parva

was not reported in the early studies of the

Mollusca of the Duck River in Tennessee (Ort-

mann, 1924) or the Cahaba River in Alabama

(van der Schalie, 1938). These mussels are the

smallest members of the Unionidae; our largest

specimen measured 40 X 27 mm.

In addition to two species of fingernail clams

from the family Pisidiidae (formerly Sphaeri-

idae), Eupera cubensis and Sphaerium rhom-

boideum, the profundal region also contained the

Asiatic clam Corbicula manilensis. This is the

first recorded sighting of Corbicula in the in-

terior reservoirs of Mississippi. An occasional S.

rhomboideum was found in the snag and debris

area occupying the larger portion of the littoral

zone. Sphaerium rhomboiderim was the only

bivalve found in any abundance in the reservoir.

Representatives were most common in sampling

areas 1, 2, and 6 (Fig. 1) in the deepest portion of

the profundal zone. At the end of the study, their

population densities ranged from 4 to 20

clams/m^. The only species able to withstand the

rigors of the fluctuating littoral zone was Pro-

ptera purpairata; a few were found in beach

areas.

The largest numbers of individuals and diversi-

ty was found in the swift waters below the spill-

way. Quadnda piistulosa, Proptera purpurata.

and Lampsilis anodontoides dominated the fauna.

Of the 8 species found in the swift-flowing

habitat, Hinkley (1906) recorded 6.

Summary

The habitat alterations in the Yalobusha River

account, at least in part, for the absence of 13

species reported by Hinkley and the appearance

of 9 other species new to this immediate area.

Significant also is the complete absence of three

other genera reported by Hinkley in 1906—

Obwaria, Plagiola. and Strophitus. The restricted

area below the spillway has created a habitat

showing the most diversity and one more favor-

able to species that already occupied the river.

TTius, we feel that habitat changes, especially im-

poundment and channelization of the Yalobusha

River, have had a detrimental effect on the

previously existing population of bivalve mol-

lusks. Although some replacement fauna has oc-

curred, the number of species has declined.

ACKNOWLEDGMENTS

This paper is a contribution of the Sedimenta-

tion Laboratory, USDA SEA-AR. The research

was begun at the University of Mississippi's

Department of Biology where it was supported by

the Graduate School and the Mississippi Water

Resources Institute. It was concluded at the

UEDA Sedimentation Lab. The authors wish to

thank Jerry Hollis, John Steen, Stratford Kay, Y.

J. McGaha, and Dr. Henry van der Schalie for

assistance and Ms. Peggy Hamilton for manu-

script preparation.

LITERATURE CITED

Cooper, C. M. 1977. Abundance and production of littoral and

profundal benthic fauna in a flood control reservoir. Proc.

Mississippi Chapter of Amer. Pish. Soc. 1:25-3,3.

Goodrich, C. 1930. Goniobases of the vicinity of Muscle Shoals.

Occ Pap. Mils. Zool, Univ. Michigan, No. 209, 25 p.

Hinkley, A. A. 1906. Some shells from Mississippi and

Alabama. The Nautilus 20:52-55.

Ortmann, A. E. 1924. The naiad-fauna of Duck River in Ten-

nessee. Amer. Midland Nat. 9:18-62.

1925. The naiad-fauna of the Tennessee River

system below Walden Gorge. Amer. Midland Nat. 9:321-l?72.

van der Schalie, H. 1938. T^ie naiades (freshwater mussels) of

the Cahaba River in northern Alabama. Occ. Pap. Mus.

Zool, Univ. Michigan. No. 392, 29 p.

RESEARCH GRANTS AVAILABLE

Lerner Fund for Marine Research provides

modest financial assistance to scientists starting

careers in marine biology, exclusive of botany.

Awards are made primarily on the graduate

and postdoctoral level, and range from $200 to

$1000. In 1979, 45% of the applicants were

funded. Grants can be used for research any-

where in the world. Applications must be re-

ceived on prescribed forms by March 15th. Write

to: Lerner P^und for Marine Research, American

Museum of Natural History, Central Park West

;it 79th Street, New York, New York 10024.

Vol. 94(1)

.Januarv:^n, 1980

THE NAUTILUS 25

SEASONAL ABUNDANCE OF AMNICOLA LIMOSA (HYDROBIIDAE) EGGS

AND INDIVIDUALS IN A RHODE ISLAND POND

David H. Kesler'

Division of Biological Sciences

The University of Michigan

Ann Arbor, Michigan 48109

ABSTRACT

The seasonal abundance of Amnicola limosa (Say) (Hydrobiidae) eggs was

observed in Nonquit Pond, Rhode Island. Recrtdtment did not appear to be related

to egg density.

In the course of investigating periphyton col-

onization of glass slides, eggs of the prosobranch

snail, Amnicola limosa (Say) were observed. The

abundance of these eggs was measured at 40 cm

and 1.0 m depths in Nonquit Pond, Rhode Island.

The slides were exposed for three week periods

with new slides being exposed every week. Only

eggs containing embryos were counted.

Nonquit Pond is a shallow reservoir (mean

depth 2.3 m) with stained, acidic water (pH

5.8-7.2) of low alkalinity (<5 mg CaCOs/l). The

littoral zone bottom ranges from small pebbles to

boulders and there are few emergent macro-

phytes. Nonquit Pond is located in Newport

County, Rhode Island.

The number of eggs/dm ^ are given in Figure 1.

Amnicola eggs were first observed on May 20 in

1977 when the water temperature was 9° C. In

1978 they were first observed on May 4 at 14.5°

C. The eggs were as Berry (1943) described them,

being single, lenticular in shape with a thin

laminated crest extending across the dorsal

margin and amber in color. They were slightly

smaller than those described by Berry, being 1.16

mm long and 0.80 mm wide at their base.

Maximum densities occurred in 1977 on July

14 at the shallow (40 cm) station and on June 28

at the deep (1.0 m) station. In 1978 maximum

densities occurred on June 29 at the shallow sta-

tion and on July 13 at the deep station. The

highest density of unhatched eggs observed was

110 eggs/dm^.

Eggs were last observed on August 3 and July

20 at the shallow and deep stations in 1977. In

1978 the last slides with eggs were collected on

August 22 at both stations. Berry (1943) cites

other works in which the spawning period of

Amnicola limosa was given as April-August.

Horst and Costa (1975) give data from D. R.

Post's 1971 M.S. Thesis in which Amnicola egg

' Present address; Division of Biologj' and Medicine. Brown

University, Box G, Providence, Rhode Island 02912.

FIG. 1. An\nicola limosa egg density (numher/dm') collected

on glass slides in Nonquit Pond, Rhode Island at iO cm

(shallow) and 1.0 m (deep) stations.

26 thp: nautilus

January m. 1980

Vol. 94(1)

FIG. 2. Amnicola limosa mean weight at iO cm and l.O m in

1977 in Nonquit Pond, Rhode Island.

FIG. 3. Amnicola limosa mean weight at J,0 cm and 1.0 m in

197S in Nonquit Pimd, Rhode Mand.

production and breeding period appear consistent

with the few published observations of this

species.

The seasonal variation in egg numbers was

similar in 1977 and 1978, although 1978 egg den-

sities were higher at the shallow station. If egg

density was tightly coupled with recruitment,

and survivorship remained constant between

years, there should have been more small snails

in August 1978 than 1977, Snails were collected

from the slide holder surfaces which provided a

larger sampling area (350 cm^ each) than the

slides. The mean snail densities in 1978 and 1977

in August at the shallow station were 10.4 and

64.5 snails/dm^ respectively, opposite the

predicted trend based on egg densities. The den-

sities at the deep station in 1978 and 1977 were

16.4 and 24.0 snails/dm^ respectively. These den-

sities were much higher than those reported by

Horst and Costa (1975) for Amnicola limosa in

McCargo Lake, New York.

The mean snail weights, an indication of the

proportion of small snails on the slide holders,

are given in Figures 2-3. The fairly constant

mean .snail weights in 1978 reflected the paucity

of small snails collected. Conversely, in 1977 the

mean snail weight clearly decreased as recruits

entered the population. If samples from the slide

holders are assumed to be equally biased between

years, these data indicate a higher mortality

following hatching in 1978. This period in their

life history has been suggested by Hunter (1961)

to be one in which snails suffer a high mortality

rate.

It is hoped that these data will stimulate

demographic investigations of Amnicola limosa

populations. This species is capable of exerting an

influence of periphyton species composition and

standing crop (Kesler, 1979), yet its basic ecology,

like many other freshwater snails is unknown.

LITERATURE CITED

Berry. E. G. 19413. The Amnicolidae of Michigan: distribution,

ecolog>'. and taxonomy. Misc. Pub. Mus. Zool.. Univ. Mich.

No. 57. 68 pp.

Horst, T. J. and R. R. Costa. 1975. Seasonal migration and

density patterns of the freshwater snail Amnicola limona.

77ip.V«i(h7».s89:56-.59.

Hunter. W. R. 1961. Annual variations in the growth and

density in natural populations of freshwater snails in the

west of Scotland. Pi'oc Zool. Soc Lond. 136:219-2.53.

Kesler. D. H. 1979 Ecological implications of grazing by Am-

nicola limosa (Say) (Hydrobiidae). In preparation.

Vol. 91(1)

January 30. 1980

THE NAUTILUS 27

MORPHOLOGICAL NOTES ON OREOHELIX AMARIRADIX PILSBRY, 1934

(PULMONATA: OREOHELICIDAE)

H. Lee Fairbanks'

Department of General Biology

University of Arizona

Tucson, Arizona 85721

ABSTRACT

A population o/Oreohelix amariradix Pilsbry. 1934 was located near Lolo. Mon-

tana. The anatomy of the pallial region and the reproductive system is described.

Comparisons are made between 0. amariradix and the members of the 0. jugalis

complex.

Bleached shells of Oreohelix amariradix were

first collected by M. J. Elrod in the Bittei-root

Mountains near Lolo, Montana. Elrod (1902)

thought that these shells were a variety of

Pymniiihihi strigosn. Shell specimens sent to H.

A. Pilsbry were later described, tentatively, as a

new species, Oreohelix amariradix (Pilsbry, 1934).

The internal anatomy was not available to

Pilsbiy . thus the rank of species was not definite.

The type locality was given as follows: Bitter-

root Mountains, along bluffs of Lf)lo Creek at

5000 feet, approximately 16 or 17 miles southwest

of Missoula, Montana. Using data obtained from

the collection of M. L. Walton, a small population

of Oreohelix amariradix was located 4.5 miles

west of Lolo, Montana (approximately 16 miles

from Missoula) on the north side of U. S. High-

way 12 and Lolo Creek. The locality, taken from

a USGS topo map (Carlton Lake Quadrangle), is

SW> 4 of SE' 4 of section 36 Tr2N R21W Missoula

County, Montana, elevation approximately 3550

feet. Shell specimens have been sent to the

Academy of Natural Sciences in Philadelphia,

ANSP 347820.

The site is located on a grassy south facing

slope overlooking Lolo Creek. The primary

vegetation, other than bunch grasses (Festnca

sp.), is composed of Ponderosa Pine (Pinus

ponderosa). Service Berr>' (Amelanchier canaden-

sis), and Nine Bark (Ph y.'<oca7^}us malvacconsj.

The snails were found in small rock slides scat-

tered along the face of the slope.

Specimens collected on 29 May 77 were com-

pared with three topotypes obtained from the

Academy of Natural Sciences in Philadelphia and

also with the description of the type specimen

(Pilsbry, 1934) (Table 1 and Figs. 1-6). Shell

sculpture and shape were similar, with no dis-

cernible discrepancies. These comparisons plus

the locality data lead to the conclusion that the

specimens collected at the above locality are

specimens of Oreohelix amariradix.

In March, 1978, three live specimens were

TABLE 1. Shell measurements of Oreohelix amariradix.

Measurements, in mm. are mean ± one std. dec. and the

range.

Type

Topotypes

(3)

Lolo, Mt.

Specimens

(21)

Height

Height,,--

-- Diameter

Diameter of

Umbilicus

14.5

8.5

.5862

' Present address: Pennsylvania State University, Beaver

Campus. Brodhead Rd., Monaca, PA 15061.

Number of

rniorls

Embryonic

Whorls

5.33

2.33

28 THE NAITILCS

January 30, 1980

Vol. 94 (1)

TABLE 2. Measuremeiiln of npniductive syatems (.1) nf

Oreohelix amariradix. LF2:il-l. 2. and .1 Measurements, in

mm. are the mean ± one aid. dev.. and the range.

Penis (total length)

pustulose portion

ridged portion

Epiphallus length

Penial retractor length

9.2 - 0.67

8.7 - 10.0

4.0 i 0.36

3.7 - 4.4

5.3 - 0.31

5.0 - 5.6

3.8

3.0

0.71

4.4

6.5 - 1.15

5.4 - 7.7

FKiS. 1-t). 1, 2, and 3 show a topotype of Oreohelix

amariradix Pilsbry, im, ANSP S.%291. 4, 5. and 6 i<how a

specimen ofO. amariradix, LF2.31-3, collected near Loin. Mon-

tana. X 2.

drowned and then dissected for anatomical

studies. No significant differences were found

between these three specimens.

The pallial region (Fig. 7) has a well developed

mantle gland without apparent vascularization

from the pulmonary vein. The kidney is tri-

angular, with its narrow end bent toward the

MG

-HV

FIG. 7. Pdlial region o/ Oreohelix amariradix, LF2,'il-.% col-

lected near Lolo. Montana (camera lurida drairing). Scale line

equals 1 mm. A = anus. H = heart. HG = hindgut. HV —

pulmonary vein, I = intestine. K = kidney. KD = closed

portion of ureter, KS = ureteric sulcus, KX = opening of

closed portion of ureter. MC = mantle collar. MG = mantle

gland.

Vol. 94(1)

January 30, 19«()

THE NAUTILUS 29

hindgut. The intestinal loop lies over the prox-

imal margin of the kidney. The closed portion of

the ui-eter begins in the curve formed by the

bending of the narrow end of the kidney, and ex-

tends approximately two thirds of the length of

the kidney. The long recurved ureteric sulcus is

bordered by a renal ridge on the hindgut and an

afferent vein. The heart is typical.

Data concerning the genitalia (Figs. 8 & 9 and

Table 2) are as follows: The lobes of the ovotestis

are angled to the shell axis, and the ovotestis

duct is relatively tightly coiled. The talon, taken

here to mean the receptaculum seminis and

fecundation pouch of Bayne (1973), albumen

gland, and prostate are typical. The spermatheca

is moderately swollen at the base, the sper-

matheca! duct is long and slender, and the head

is ovoid and bound to the area just proximal of

p

FIG. 8. Genitalia of Oreohelix amariradix. LF2S1-S, mllected

near Lolo. Montaiia (camera lucida drawing). Scale line

equals 1 mm. DG = prostate, E = epiphallm. G = ovotestis.

GD = ovotestis duct, GG = albumen gland, GT = talon. P

— penis. PR = penial retractor muscle, S = spermatheca.

UT = uterus. UV = free oviduct, V = vagina. VD = va.f

deferens.

HG. 9. Penial chamber of Oreohelix amariradix, LF2.11-S,

collected near Lolo, Montana (camera lucida drawing). Scale

line equals 1 mm. E = epiphalhis, P = penis. PP = penial

pilaster.1, PR = penial retractor muscle. PV = penial verge,

V = vagina, VD = vn.^defereu.'i.

the end of the uterus (spermoviduct of some

authors) by connective tissue. The vagina is about

equal in length to the free oviduct and has low

ribbing internally. The vas deferens is bound by

connective tissue to the peni-vaginal angle, and

the expansion of the vas deferens into the

epiphallus is abrupt. The epiphallus is con-

siderably shorter than the penis (Table 2). The

penial retractor muscle is inserted at the junction

of the penis and the epiphallus. The penis is

slender with the interior ridged portion more

than half the total length of the penis (Table 2

and Fig. 9). The penial verge is prominent, with

its opening at the tip of the verge.

The radula has 25-28 teeth per half row, and

the central tooth is tricuspid.

Ten newborn Oreohelix amariradix were found

in the terrarium in which the adults over-

wintered. The shells were transparent and ap-

30 THE NAUTILUS

January 30. 1980

Vol. 94(1)

peared to lack surface sculpture. Measurements

of the shells produced the following data: Mean

number of whorls = 2.18 (range 2-2.33), mean

diameter = 3.12 mm (range 2.7-3.4).

DISCUSSION

Piisbry (1939, p. 500) suggested that live

specimens of Oreahelix anidri radix and O. junalis

be compared. Solem (1975), in a discussion of the

0. jiiydlis complex, gave both .shell and anatom-

ical data that can be compared to the data pre-

sented here.

The shell of Oreohelix jugaiis (24 mm) is not

only larger than that of O. amuriradix (14.5 mm)

but is different in proportions as well. The data

for the genitalia also show significant differences.

For example, 0. jngalis has an epiphallus that is

more than half the length of the penis, but in 0.

amariradix the length of the epiphallus is only

41% of the penial length (Table 2). Also, the penis

of 0. jutjalk is shorter than that of 0.

(imarimdix. There are also ecological differences

between these two taxa; 0. jnyalif: is found in

"large boulder piles or cliff base talus within the

flood zone of the Salmon River" (Solem, 1975). 0.

amariradix is found in shallow talus on a south

facing slope, a much drier and less sheltered

habitat than that nfO.jiinalis.

According to Piisbry (1939), Oreohelix vortex.

0. intersum. and probably 0. junii are members

of the jnnnlis complex, thus comparisons of these

species with 0. amariradix seem pertinent.

The reproductive system of Oreohelix vortex

has the pustulose portion of the penis much

longer than the ridged portion (Solem, 1975). Tliis

is not true of 0. amariradix (Table 2). In addi-

tion, the position of the penial verge opening is

different in these two taxa.

The shell of Oreohelix internum is markedly

different from that of O. amariradix becau.se of

the radial striae found on the shell of O. iider-

siim. In addition, the reproductive system of O.

intersum is similar to that of O. vortex (see

above).

It is clear that Oreohelix amariradix is distinct

from O.JHiialix. O. vortex, and O. intemum.

Comparisons between Oreohelix amariradix

and 0. junii show that 0. junii has a shell that is

larger, has a more depressed form, and appears

smcx)ther than the shell of 0. amariradix. The

reproductive systems are quite similar: the only

notable differences are the folding of the vas

deferens and the somewhat shorter epiphallus

found in 0. junii. The localities of these two taxa

are approximately 275 miles apart and are eco-

logically different. These differences are probably

sufficient to indicate that the two ta.\a are dif-

ferent species. Thus, Pilsbr>''s designation of

Oreohelix amariradix as a species is confirmed.

ACKNOWLEDGMENTS

I wish to thank Dr. Walter B. Miller and Dr.

Carl C. Christensen, both of whom provided

valuable comments during the writing of this

paper. I also wish to thank the Academy of

Natural Sciences in Philadelphia for the loan of

the topotypes of Oreohelix amariradix. Tlianks

also go to Dr. Royal B. Brunson for initiating my

interest in 0. amariradix.

LITERATURE CITED

Bayne, C. .J. 197.3. Physiology of the pulmonale reproductive

tract: Location of spermatozrei in isolated, self-fertilizing

succinid snails. Vcliifir l6:Uii)-\7h.

F^lnid, M. .1. liXI'i. A biological rwonnais.sance in the vicinity

of Flathead Lake. Bull. Uiiii: Montana No. 10, pi. 27.

Piisbry, H. A. 1934. Notes on the anatomy of Oreohelix. IIL

With descriptions of new species and subspecies. Proc. Acad.

Nat. Sci. Phil. S5-::m-im.

1939. Land Molluura of North America (North of

Mexico). Acad. Nat. Sci. Phil. Monographs No. -3. Vol. 1,

Part 1: .500.

Solem, A. 1975. Notes on Salmon River Valley oreohelicid

land snails with dp,scription of (hriihrti.r waltoni. Veliger

18:16-31.

Vol. 91(1)

January 30, 1980

THE NAUTILUS 31

CALIBRATION OF AMINO ACID RACEMIZATION IN LATE PLEISTOCENE

MOLLUSKS: RESULTS FROM MAGDALEN A BAY, BAJA CALIFORNIA

SUR, MEXICO, WITH DATING APPLICATIONS AND

PALEOCLIMATIC IMPLICATIONS

John F. Wehmiller

Department of Geology

University of Delaware

Newark, DE 19711

William K. Emerson

and Department of Invertebrates

American Museum of Natural History

New York, NY 10024

ABSTRACT

Amino add enantiomeric (D/L) ratios in late Pleistocene, marine mollusks from

three uranium-series dated localities (Cay^icos and the San Diego Nestor Terrace

in California and the Magdalena Terrace in Baja California Sur) provide calibra-

tion points for establishing a 120,000-year isochron for interpolation of amino acid

age estimates over a broad latitudinal range (35° N. to £4° N. lat.) of the Califor-

nia - Baja California continental borderland.

Leucine enantiomeric ratios in specimens of the bivcdve Chione from the

Magdalena Terrace, compared with ratios predicted by a kinetic model for

120.000-year samples with constant (modem) diagenetic temperature, indicate

slight paleotemperature reductions (r-2° C) at Magdalena Bay during late

Pleistocene glacial episodes in the northern hemisphere.

There has long been a need to date more pre-

cisely Quaternary marine deposits in order to

understand faunal composition and rates of tec-

tonic deformation. Though uranium-series dating

methods have been applied to such problems,

significant uncertainties have been encountered

when applied to mollusks, the most commonly

found macroinvertebrates in mid-latitude terrace

deposits (Kaufman, et al. 1971; Szabo and Ved-

der, 1971; Ku and Kern, 1974). Consequently,

other methods, particularly techniques suitable

for mollusk dating, have been sought for those

localities that lack corals, the most reliable

organisms for uranium -series dating.

Amino acid racemization methods have been

shown to serve as both a relative and semi-

quantitative dating tool for Quaternary mollusks

from both the Atlantic and Pacific coasts of the

United States (Mitterer, 1974, 1975; Belknap, MS;

Wehmiller, et at. 1977, 1978; Kennedy, MS). It

has been shown that enantiomeric ratios (i.e..

ratios of the D- and L-enantiomers of individual

amino acids) increase with age in stratigraphic

sequences of Pleistocene samples from the

California continental borderland: Palos Verdes

Hills (Mitterer and Hare, 1967), San Nicolas

Island (Wehmiller, et al, 1977), San Francisco

Bay (Atwater, MS), the Los Angeles Basin

(Wehmiller et al, 1977), and the Ventura Basin

(Wehmiller et al, 1978). On the California coast

well-established 120,000 to 125,000 year U-series

dates on corals from Cayucos (35.3° N.) and the

Nestor Terrace on Point Loma (32.7° N.) permit

evaluation of latitude/temperature effects on

racemization kinetics (Wehmiller, et al, 1977;

Wehmiller and Belknap, 1978). Amino acid data

for localities with U-series absolute dates permit

the evaluation of kinetic models of molluscan

amino acid racemization (Wehmiller, et al.. 1977;

Wehmiller and Belknap, 1978). These models re-

quire comparisons of estimated late Pleistocene

temperature histories with available quantitative

paleoclimatic data for glacial-age temperature

reductions. Kinetic models are especially impor-

tant for age estimation in cases where local inter-

polations between calibrated results cannot be

made, owing to the lack of absolute dates for the

intermediate localities.

In this paper we report amino acid data for a

third uranium-series dated locality, at Magdalena

32 THK NAUTILUS

Januan-3n, 1980

Vol. 91(1)

Bay, on the Pacific coast of Baja California Sur

(24.6° N. latitude). The combined results

presented here more than double the latitudinal

range for which calibrated amino acid data can

now be interpolated.

Localities, Samples, Analytical Results

Three samples of the venerid bivalve mollusk

Chione of. C. undatella (Sowerby, 1835) from the

Magdalena Terrace, Magdalena Bay, (Figure 1,

AMNH loc. F-6) Baja California Sur, have been

analyzed for amino acid enantiomeric ratios. U-

series coral analyses from this marine-cut terrace

(Omura, et al. 1979) indicate that this locality is

approximately 120,000 (120 ka) yrs. in age and

correlative with the early portion of isotopic

Stage 5 (substage 5e of Shackleton and Opdyke,

1973). This particular time is well-represented by

emergent terraces around the world (see Bloom,

et al, 1974, for example).

Amino acid analyses have been performed ac-

cording to procedures described elsewhere

(Wehmiller et al, 1977; Kvenvolden, et al., 1972;

Frank et al., 1977). Enantiomeric ratios have

been determined by capillary column gas chroma-

FIG. 1. Index map of the. Mmfdalena Bay-Aimejas Bay area uf

Baja California Sur. Mexico, showing fossil localities (AMNH

Iocs. F-5 to F-8) in the late Pleistocene Magdalena Terrace

described by Omura. et al.. (1979). U-series dated specimenx

(corals and echiwnds. Omura et al.. 1979) and amino acid

enantwmeric dated specimens Chione) form coexvitiny

samples collected at locality F-6. AMNH Loc. F-6. about 1.5

km mrrth of the village of Puerto Magdalena (ti'SlfN..

USOSf W.). Santa Magdalena peninsula. Baja California Sur;

fosidh collected by W. K. Emerson, March 17. 1957 ( =

California Academy of Scienees locality 75i: .lee Jordan. 1936.

tography of the isopropyl-NTFA derivatives of

the total amino acid mixture. The chromato-

graphic method employs a 25 m glass capillary

column similar to that used by Frank et al

(1977) and marketed under the name Chirasil-Val

(Applied Science Laboratories, State College, PA).

Gjlumn conditions were as follows: He carrier,

12.0 psi; program isothermal at 90° C. for 16',

r/min. to 135° C, 32' isothermal. A represen-

tative chromatogram is shown in Figure 2. This

analytical method represents an alternative to

the (-l-)-2-butyl-NTFA method used for most

previous gas chromatographic studies of fossil

amino acid enantiomeric ratios (Kvenvolden, et

al, 1972. 1973; Wehmiller, et al.. 1977). Com-

parison of the two methods shows a good agree-

ment (within 2 to 5%) for most amino acids

(Wehmiller, unpublished).'

Enantiomeric ratios for six amino acids for

samples from Magdalena Bay are given in Table

1. The data represent mean values of peak-height

determinations from at least two chromatograms

for each sample. The results (Table 1) demon-

strate good reproducibility and are consistent

with relative intrageneric racemization rates in

comparison with previous observations

(Wehmiller, et al, 1977; Lajoie, et al. in press),

thereby meeting the two available criteria for

data reliability.

DISCUSSION

'^or purposes of discussion, results for only one

amino acid, leucine, are considered here. Kinetic

models for leucine racemization have been most

' Current work at the University of Delaware on the com-

parison of these two analytical methods indicates the follow-

ing relationship for leucine:

D/L leucine (Butanol) = 1.029 [D/L leucine {isopropanoi)]

-I- 0.0 M

r = .993, n = 48 samples ( of 5 genera)

These comparisons have been made by splitting a single

sample hydrolyzate, after all desalting steps, into two aliquots

for esterifation with either the (-(-) -2— butanol or the

isopropanoi.

The only amino acid for which significant deviations be-

tween the two methods are observed is phenylalanine: D/L

values determined by the isopropanoi method are about 15-

20% less than those determined by the (-l-)-2-butanol

method.

Vol. HMD

January •'^0,1 9Sn

THK NAUTILUS -33

to

z

o

a.

<f)

UJ

q:

tr

o

O

"T"

15

-| —

30

45

60

-| —

75

TIME, min.

FIG. 2. Chromatogram of isopr<ypyl-NTFA derivatives of

amino acidg in Chione. (Magdalena Terrace Sample 79-33-2)

on 25 m Chirasil-val optically active column. Peak identifica-

tion as follows: 1, 2, D, L alanine: 3, i, D, L valine: ft D-

alloisoleucine: 7, L-isoleucine: 8, D + L proline: 9, 10 D. L

leucine: 11, 12, D. L aspartic acid: 13. 15 D, L phenylalanine:

14, 16, D, L glutamic add Program: 90', Iff isothermal;

I'/min. to 135°; 32! isothermal. He carrier gas pressure, 12

psi.

thoroughly evaluated (Wehmiller and Belknap,

1978), though such models can easily be developed

for other amino acids using observations of in-

trageneric relative racemization rates (Lajoie, et

al., in press).

In Figure 3, the leucine data for the Mag-

dalena Bay Chione are compared with leucine

data in the venerid bivalve Protothaca from the

Cayucos and Nestor Terrace calibration localities

in central and southern California. Available

evidence indicates that Protothaca and Chione

have leucine racemization kinetics that are iden-

tical within analytical uncertainties (Lajoie, et uL,

in press). The leucine data are plotted vs. pres-

ent mean annual air temperatures at each local-

ity, in order to demonstrate the latitude/tem-

perature effect on enantiomeric ratios in samples

of similar age. Plots of enantiomeric ratios

against latitude would have similar appearance

(Wehmiller, et al, 1977; Kennedy, MS). Also

shown in Figure 3 are the leucine D/L curves

predicted by the kinetic model of Wehmiller and

Belknap (1978) for samples with ages of 80, 120,

and 200 ka, for effective ground temperatures

that would be associated with the present mean

annual air temperatures shown on the abscissa of

Figure 3. Implicit in these model isochrons are

assumptions about the temperature dependence

of the racemization reaction and, more im-

portantly, about the relation between ground and

air temperatures at coastal localities. For pur-

poses of construction of model isochrons, it has

been assumed that these ground-air temperature

relationships are constant over latitude and

through time (Wehmiller, et al, 1977). Mean an-

nual air temperatures are used in Figure 3

because these data are more easily obtained than

ground temperature, though the actual ground

temperature at any site might be a few degrees

warmer (see Wehmiller, et al, 1977: 13-17, 52-54,

TABLE 1. Amino add enantiomeric (D/L) ratios' in Chione

samples from Magdalena Bay. Baja California Sur, Mexico.

All spedmens from AMNH locality F-6: sample numbers

79-33-2 and 79-33-2A from two articulated valves of the same

spedmen.

' Amino acid abbreviations:

LEU Leucine PHE Phenylalanine

GLU Glutamic acid ASP Aspartic acid

VAL Valine ILEU Isoleucine (D-alloisoleucine/

ALA Alanine L-isoleucine)

^n.m. not measured

■ Ratios are averages of peak height ratios determined from

at least two chromatograms of each sample. Precision of

multiple determinations is between 2% and 6%, depending on

amino acid.

34 THE NAUTILUS

January 30, 1980

Vol. 91(1)

10 12 14 16 18 20 22 24

PRESENT MEAN ANN TEMP, °C.

FIG. 3. Fiot of D/L leucine vs. mean annual air temperature

and latitude for three U-series dated (ca. 120 ka) calibration

localities: C. Cayucos: N, Nestor Terrace: MR Magdaletm

Bay. Data for Cayucos and Nestor Terrace are on Protothaca

(Wehmiller. et al., 1977y Data for Magdalena Bay are on

Chione, a genus thought to have racemizaiion kinetics iden-

tical urith those of Protothaca (Lajoie. et al., in press).

Leucine data for Chione have been factored upward by about

39/o (see equation in text) for direct comparison of different

analytical methods employed for these residts. Temperature

data from summary in Wehmiller. et al., (1977) and Hastings

(196U). Size of data points represents ± 5%, the typical uncer-

tainty expected for multiple aiudyses at a single locality (see)

Wehmiller et al., 1977t Table 5).

Solid line represents the U-series calibrated isochron, fixed

to actual analytical residts and assigned an age of 120 ka.

Dashed lines represent model isorhrons, drawn from the

kinetic model of Wehmiller and Belknap (1978) for constant

effective temperatures as indicated. The separation between

the model and actual i'iochroiui for 120 ka is interpreted as

the kinetic consequence of late Pleiitocene temperature reduc-

tions, which would have slowed the racemizalion reaction and

lowered the effective temperature for Pleistocene samples

compared with modem samples.

Table 2; Wehmiller, 1977). Uncertainties in

ground-air temperature relations are probably

minor for comparison of marine terrace amino

acid data from closely-spaced localities, but these

uncertainties become more important when con-

sidering results (such as those presented here) for

samples from a broad latitudinal range.

The solid line in P^igure 3 represents the

120,000 year U-series calibrated isochron. No

assumptions regarding kinetic models are needed

to interpret data that fall on this isochron, if it is

assumed that samples in this latitudinal range

have been exposed to similar fluctuations in

paleotemperature during late Pleistocene climatic

cycles.

The divergence between the 120 ka kinetic

model curve and the actual calibrated curve

demonstrates the effect of late Pleistocene

temperature reductions on the racemization proc-

ess (Wehmiller and Belknap, 1978). For example,

the Nestor Terrace data plot about 0.06 lower

than would be predicted by the kinetic model if

these samples had always been exposed to con-

stant (modem) effective temperatures (those

associated with the present mean annual air

temperature of 16° C). The Nestor (32.7° N.) data

would fall on the model 120 ka isochron for an ef-

fective Pleistocene temperature of about 13.5° C;

the 2.5° C. difference between the effective

Pleistocene temperature and the present effective

temperature is considered to be the kinetic effect

of full-glacial temperature (air and/or ground)

reductions of about 5° C. The timing of these

paleotemperature reductions is based on the

glacial minima-maxima model of Shackleton and

Opdyke (1973). For a given locality, the full

glacial temperature reduction would always be

greater than the effective Pleistocene tem-

perature reduction, because the latter represents

the average kinetic effect of all temperatures to

which the sample has been exposed during its

fossil history. A full discussion of the optional

temperature histories that would be consistent

with this effective temf)erature reduction is found

in Wehmiller, et al (1977, 61-66). The Cayucos

(35.3° N.) data suggest a similar temperature

reduction: the parellelism of the calibrated and

the model isochrons between 36° N. and 32° N. in-

dicates that reductions in effective temperature

(and possibly, therefore, of temperature itself)

have been similar over this latitudinal range dur-

ing the past 120,000 years.

The Magdalena Terrace (24.6° N.) data lie

much closer to the 120 ka model isochron than do

the Cayucos and Nestor data, and indicate effec-

tive paleotemperature reductions were about 1.0°

C, representing full glacial temperature reduc-

tions of no more than 2.0° C. The convergence of

U-series calibrated isochron and the model

isochron at more southerly latitudes indicates

that greater paleotemperature reductions have

occurred in southern California than in southern

Baja California. Though the magnitude of this

change in the paleotemperature gradient can be

only qualitatively estimated because of the broad

Vol. 94 (1)

January 30. 1980

THE NAUTILUS 35

latitudinal range over which the model isochrons

(with their assumptions of constant ground-air

temperature relations) are being extrapolated,

the paleotemperature estimates derived from

Figure 3 are reasonable in comparison with

paleoclimatic information for both coastal and

nearshore marine environments between 36° and

24° N. latitude (CLIMAP, 1976; Peterson, et a/.,

1979).

CONCLUSIONS

Amino acid enantiomeric ratios in mollusks

from three U-series dated marine terrace sites

between 36° and 24° N. latitude on the Pacific

coast provide a calibrated isochron for samples

approximately 120,000 years in age over a wide

range of modem mean annual temperatures (ap-

proximately 9° C). The availability of this

isochron should aid in the dating of late

Pleistocene terrace localities at intermediate

latitudes by interpolation of data between

calibration points.

Comparison of the U-series calibrated isochron

with kinetic model isochrons indicates that

greater paleotemperature reductions have oc-

curred in coastal California than in southern Ba-

ja California during some part of the past 120,000

years, probably during times of maximum glacial

advance. The consistency of the Magdalena Bay

results with independent paleoclimatic informa-

tion supports the kinetic models that are in use

for the quantification of age/temperature rela-

tionships of amino acid racemization data in

Quaternary mollusks from Pacific coast marine

terraces.

ACKNOWLEDGMENTS

We are indebted to George L. Kennedy, U. S.

Geological Survey, Menlo Park, California, for

critically reading the manuscript and confirming

the identification of the specimens. Everly

Keenan, University of Delaware, ran the x-ray

analysis of the samples and reviewed the

manuscript. Laura Carpenter and Linda Ahem,

University of Delaware, and William E. Old, Jr.,

American Museum of Natural History, aided in

the preparation of the manuscript. Amino acid

research at the University of Delaware is sup-

ported by U. S. Geological Survey Grant No.

14-08-000 1-G592.

LITERATURE CITED

Atwater, B. F. MS. Attempts to correlate late Quaternary

climatic records between San Francisco Bay. the Sacra-

mento-San Joaq\iin Delta, and the Mokelumne River,

California. Dept. of Geology, Univ. Delaware, 1-240, (1980)

Belknap, D. F. MS. Application of amino acid geochronology

to stratigraphy of late Cenozoic marine units of the Atlan-

tic coastal plain. Ph.D. Lhssertation, Dept. Geology. Univ.

Delaware, 1-.5.32 (1979).

Bloom, A. L., W. S. Broecker. J. M. A. Chappell, R. K. Mat-

thews, and K. J. Mesolella. 1974. Quaternary sea level fluc-

tuations on a tectonic coast: New "Th/^'U dates from the

Huon Peninsula, New Guinea. Quat. Res. 4:185-205.

CLIMAP. 1976. The surface of the ice-age earth. Science

191:1131-1137.

Frank, H., G. J. Nicholson, and E. Bayer. 1977. Rapid gas

chromatographic separation of amino acid enantiomers

with a novel chiral stationary phase. Jnur. Chrom. Sci,

15:174-176.

Hastings, Jr. R. 1964. Climatological data for Baja California.

Univ. Arizona, Inst. Atmospheric Physics, Technical

Reports on the Climates of Arid Regions. No. 14:1-132.

Jordan, E. K. 1936. The Pleistocene fauna of Magdalena Bay,

Lower California. Contrib. Dept. Geol. Stanford Univ.

1:103-173.

Kaufman. A.. W. S. Broecker. T. L. Ku, and D. L. Thurber.

1971. The status of U-series methods of moUusk dating.

Georhim, Cosmochim. Acta 35:1155-1183.

Kennedy, G. L. MS. Pleistocene paleoecology, zoogeography,

and geochronology of marine invertebrate faunas of Pacific

northwest coast (San Francisco Bay to Puget Sound). Ph.D.

Dissertation Dept. Geology, Univ. California, Davis, p.

1-824, (1978).

Ku, T. L, and J. P. Kern. 1974. Uranium-series age of the up-

per Pleistocene Nestor Terrace, San Diego, California. Geol.

Soc.Amer. Bull. 85:1713-1716.

Kvenvolden, K. A., E. Peterson, and G. Pollock. 1972.

Geochemistry of amino acid enantiomers: gas

chromatography of their diastereoisomeric derivatives. In,

Adv. Organic Geochemistry for 1971: p. 387-401. H. R. von

Gaertnerand H. Wehner [eds.]. Pergamon Press.

J. F. Wehmiller, and P. E. Hare.

1973. Racemization of amino acids in marine sediments

determined by gas chromatography. Geochim. Cosmochim.

Acta 37:'2215-2225.

Lajoie, K. R.. J. F. Wehmiller, and G. L. Kennedy. In press.

Inter- and intrageneric trends in apparent racemization

kinetics of amino acids in Quaternary mollusks. In, Adv.

Biogeochemistry of Amino Acids. P. E. Hare, T. C. Hoering,

and K. King, Jr. [eds.]. John Wiley.

Mitterer, R. M. 1974. Pleistocene stratigraphy in southern

Florida based on amino acid diagenesis in fossil

Mercenaria. Geo/og;/ 2:425-428.

3fi THE NAUTILUS

January 30. 1980

Vol. 94(1)

1975. Ages and diagenetic temperatures of

Pleistocene deposits of Florida based upon isoleucine

epimerization in Mercenaria. Earth Planet Set. Letters

28:275-282.

and P. E. Hare. 1967. Diagenesis of amino acids

in fossil shells as a potential geochronometer [Abst.]. Ge<il.

Soc.Amer. Pr<K)mms. 196? Ann. Meeting, p. 152.

Omura, A., W. K. Emerson, and T. L. Ku. 1979. Uranium-

series ages of echinoids and corals from the upper

Pleistocene Magdalena Terrace, Baja California Sur, Mexico.

77ieiVa!i/i7».s- 93: 184-189.

Peterson, G. M.. T. Webb III. J. E. Kutzbach, T. van der Ham-

men, T. A. Wijmstra. and F. A. Street. 1979. The continen-

tal record of environmental conditions at 18.000 yr. B.P.: an

initial evaluation. y!ra/. Rea. 12:47-82.

Shaekleton, N. J. and N. D. Opdyke. 1973. Oxygen isotope and

palaeomagnetic stratigraphy of equatorial Pacific core

V2.3-238: Oxygen isotope temperatures and ice volumes on a

10* year and 10* year scale. Qimt. Res. 3:.39-5.5.

Szabo, B. J., and J. G. Vedder. 1971. Uranium series dating of

some Pleistocene marine deposits in southern California.

Earth Planet. Sci. Letters 11:283-290.

Wehmiller, J. F. 1977. Amino acid analyses of shells from the

Del Mar, California midden site: Apparent rate constants,

ground temperature models and chronological implications.

Earth Planet^ Sci. Letters 37:184-196.

and D. F. Belknap. 1978. Alternative kinetic

models for the interpretation of amino acid enantiomeric

rations in Pleistocene mollusks: examples from California,

Washington, and Florida. Quat. Res. 9:330-348.

, K. R. Lajoie, K. A. Kvenvolden, E. Peterson. D.

F. Belknap, G. L. Kennedy, W. 0. Addicott, J. G. Vedder,

and R. W. Wright. 1977. Correlation and chronology of

Pacific coast marine terraces of continental United States

by amino acid stereochemistry: technique evaluation,

relative ages, kinetic model ages, and geologic implications.

U. S. GeoL Stin: Open-Pile Rept. 77-680:1-191.

, A. M. Sama-Wojcicki, R. F. Yerkes,

G. L. Kennedy, T. A. Stephens, and R. F. Kohn. 1978.

Amino acid racemization dating of Quaternar}' mollusks.

Pacific coast United States. In. Short Papers of the Fourth

International Conference, Ge(x;hronolog>\ Cosmochronology,

Isotope Geology 1978, R. E. Zartman [ed.]. U. S. GeoL Sun:

Open-File Rept. 78-701:445-448.

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THE

NAUTILUS

Volume 94, number 2 — April 30, 1980

ISSN 0028 -1344

CONTENTS

John H. Himmelman

Reproductive Cycle Patterns in the Chiton Genus, Mopalia (Polyplacophora) 39

Douglas G. Smith

Goniobasis virginica (Gastropoda: Pleuroceridae) in the Connecticut River 50

Harlan K. Dean

Microstructureof the Crystalline Style of Spisw/asoMtssiima (Bivalvia: Mactridae;) 54

R. N. Howard, B. Z. Lang, and R. L. Carr

A New Preparation for Obtaining Chromosome Smears in Hydrobia (Hydrobriidae) 58

Stephen A. Hall

Snails from Quaternary Valley Fill at Chaco Canyon, New Mexico 60

Elizabeth C. Dudley and E. Christopher Dudley

Drilling Predation on some Miocene Marine Mollusks 63

William K. Emerson

Invertebrate Faunules of Late Pleistocene Age, with Zoogeographic Implications, from Turtle Bay,

Baja California Sur, Mexico 67

Ralph W. Taylor

Freshwater Bivalves of Tygart Creek, northeastern Kentucky 89

Publications Received ii Obituary

Meetings 66

PUBLICATIONS RECEIVED

Evolutionary SystenuUics of Bivalve Molluscs (edited by C. M.

Yonge and T. E. "niompson). 1978. Philos. Trans. Royal S<x'.

London, sect. B, vol. 284, pp. 199-436. 18 papers of major

significance in the systematics, evolution and paleontology

of the Bivalvia by leading malacologists.

Sarasua, H. and J. Espinosa. 1978. Adiciones al Genero Murex

(Mollusca: Neogastropoda) Pneyana. no. 179, pp. 1-13. A

brief review of Cuban Murex without reference to recent

literature. Murex yiimurinus n. sp. bears close resemblance

to springeri Bullis, perelegans Yokes, and riboiwy Clench

and Farfante.

Venics. The Japanese Jnunxal <if Malacology. Special Publica-

tion, 1979, Tokyo. Check List of New Genera and Species

and Author Index to vols. 1-36 (50 years). A very useful and

necessary index to about 1000 new moUuscan names pro-

posed in this well-known journal. Crucial dates of publica-

tion are given for 36 volumes.

Howorth, Peter C. 1978. The Abahtw Boot 80 pp., illus, 8 col-

or pis. Paperback. Naturgraph Publ., Happy Camp, CA

96039. .$;3..50. A delightful popular book offering identifica-

tions, biology, recipes, and ethnology of the Pacific coast

Haliotis.

Bernard, F. R. 1979. Bivalve Mollusks of the Western

Beaufort Sea. Contributions in Science, no. 313, 80 pp. $9.25

postage paid. Natural History Museum of Los Angeles

County, CA 90007. 58 species, including one new genus,

Boreacola (Montacutidae) and two new species, from the

Arctic are described and illustrated.

The Pariah, no. 6, 12 pp. P. 0. Box 42, Highstown, NJ 08520.

$1.00. Privately printed. Contains an article on Cypraea

thomasi and one on recently created synonyms in the genus

Conus.

Reproduction of Marine Invertebrates: Vol. 5, Molluscs:

Pelecypods [Bivalvia) and Lesser Classes [Aplacophora,

Polyplacophora, Monoplacophora, Scaphopoda]. Academic

Press, 1979. xvi -I- .369 pp. Edited by A. C. Giese and J. S.

Pearse. $45.50. Clothbound. An excellent, well-illustrated

review with good bibliographies. The chapter by A. N.

Sastry on Pelecypoda (excluding Ostreidae) is particularly

informative. Not unreasonably priced considering today's

publishing costs and the excellent contents.

Pathways in Malacology. 1979. 295 pp. Mited by S. van der

Spoel, A. C. van Bruggen, J. Lever. Eleven chapters, on

somewhat unrelated subjects, representing papers given at

the Sixth Congress of the Unitas Malacologica Europaea in

Amsterdam in 1977. Some of the papers are excellent and

stimulating, such as J. Lever's "On Torsion in Gastropods ",

"Cementation in the Bivalvia" by C. M. Yonge, "A Theory

of Land Snail Biogeographic Patterns Through Time" by

Alan Solem, and Fumestin's intriguing "Planktonic

Molluscs as Hydrological and E>x)logical Indicators".

Knudsen's "Deep-sea Bivalves" is an excellent, up-dated

review. Bohn. Scheltema and Holkema. Utrecht. Bound,

$72.00. An expensive way to publish a transient, albeit

valuable, symposium.

Proceedings First International Corbicula Symposium. 1979.

313 pp. Texas Christian Univ. Research Foundation. Edited

by .]. C Britton. 17 papers and a large bibliography of this

economically important, freshwater bivalve give new and

valuable information. The return to the species name of

flumima Muller, 1774, for this bivalve, variously called

manilensis and leana, is probably a very wise, expedient

decision.

Mathiak. Harold A. 1979. A River Survey of the Unionid

Mussels of Wisconsin. 1973-77. 76 pp.. 11 color pis., maps.

Paperbound. $15.00 (postpaid). Sand Shell Press. P. 0. Box

44. Horicon. WI .53032. A non-scientific over\'iew of the 45

species of freshwater clams found in 251 Wisconsin rivers.

Excellent color plates, and useful for identifications.

Bouchet. Philippe. 1979. (photography by F. Danrigal and C.

Huyghens). Sea Shells of Western Europe. 144 pp.,

Numerous color plates. American Malacologists. Inc.. P. 0.

Box 22.5.5, Melbourne. FL 32901. Hardbound. $8.95. A

beautifully illustrated ecological and life history account of

the marine shells of France, the Lowlands and southern

England.

Bulletin of the Institute of Malacology. Vol. 1, no. 1, 21 pp.

May 30. 1979. A new professional malacological publication

from Tokyo supported by the Coral Museum and several

foundations. Contains four articles by Kosuge with descrip-

tions of several new muricids and Laiiaiis. Subscribe or ex-

change publications vrith Dr. Sadao Kosuge. Institute of

Malacology. 6-36 Midoricho 3 chome. Tanashi City, Tokyo

188. .Japan.

Kandel. Eric. R. 1979. Behavioral Biology of Aplysia. A Con-

tribution to the Comparative Study of Opisthobranch

Molluscs, xiii + 463 pp., 93 illus. W. H. Freeman and Co.,

660 Market St., San Francisco, CA 94104. Paperbound,

$20.0(j; hardbound, $40.00. This remarkably well-done text-

book demonstrates how a mollusk can serve as a subject for

neurobiology, comparative behavior, and the evolution of

functional adaptation. Exquisite drawings and inspirational

text cover the physiology, life cycle, behavior, and learning

processes in the opisthobranchs. A well-produced book

worth its price.

Rajagopal, A. S. and H. P. Mookherjee. 1978. Contributions to

the Molluscan Fauna of India. Part 1: Gastropoda: Ar-

chaeogastropoda. Occasional Paper No. 12, pp. 1-48, 1 pi.

Records of the Zoological Survey of India, New Delhi

110-006. Paperback, $2.00 U. S. Keys and 60 years on k In-

dian locality records for 36 species.

Ornohorsky. Walter 0. 1979. Tropicxjl Pacific Marine Sheik.

Pacific Publications, Sydney and N. Y. 352 pp., 68 pis., 4

(Cones) in color. Approximately $28.30 U. S. This is a useful

continuation of the author's vols. 1 and 2 of Marine Shells

of the Pacific, and fills in with about 500 species not pre-

viously covered, Cieneral and regional bibliographies, a gloss-

ary and index are included. It would have helped had the

index included references to the first two volumes, for now

one has to consult three volumes when identifying any one

species.

Vol. 94 (2)

April 30, 1980

THE NAUTILUS 39

REPRODUCTIVE CYCLE PATTERNS

IN THE CHITON GENUS MOPALIA (POLYPLACOPHORA)

John H. Himmelman

Departement de biologie

Universite Laval

Quebec, Canada G1K7P4

ABSTRACT

TTie reproductive cycles of the five most common species of the chiton genus

Mopalia on the British Columbia coast are examined in three locations in relation

to environmental factors over a 3 to i year period. A diversity of patterns is evi-

dent. Mopalia ciliata starts gonadal growth in the summer, while Mopalia laevior

starts gonadal growth in the autumn. Both patterns occur in different populations

o/ Mopalia hindsii. Photoperiod and temperatute may act as environmental cues in

controlling these patterns. Spawning in M. hindsii usually occurs during the period

when temperatures are near minimal, or just starting to rise, while M. ciliata and

M. laevior spawn in synchrony with the spring phytoplankton bloom. Mopalia

lignosa has a more irregular reproductive cycle, and gonadal growth may follow

spawning in the late winter and spring, as well as summer spawning activity.

There are no obvious factors correlated mth these periods of gonadal growth and

spawning. The most irregular reproductive pattern occurs in Mopalia muscosa and

animals in mature and spent condition are found throughout the year. This may

be an adaptation to life in the intertidal zone, where favourable conditions for

gamete production and spawning may be determined more by microhabitat condi-

tions than by general hydrographic and climatic factors.

INTRODUCTION

Members of the North Pacific genus Mopalia

are a characteristic part of the inter- and sub-

tidal faunas along the west coast of North

America, but little attention has been given to

their reproductive biology and general ecology. In

the present study, the reproductive cycles of the

five most common species in British Columbia

are examined. These species are Mopalia hindsii

(Reeve, 1847), Mopalia ciliata (Sowerby, 1840),

Mopalia laevior (Pilsbry, 1918), Mopalia lignosa

(Gould, 1846) and Mopalia muscosa (Gould, 1846).

All previous studies on this genus were conducted

in California. Bamawell (1954) observed the

gonadal condition of animals of three species in

San Francisco Bay over a period of a year, and

Thorpe (1962) presented a list of times when he

observed individuals spawning for eight species

over a six year period. Studies using the gonadal

index method were made by Giese et al. (1959) on

M. hindsii in Monterey Bay, and by Boolootian

(1964) and Monroe and Boolootian (1965) on M.

muscosa in Santa Monica Bay. These repwrts do

not give a clear understanding of the reproduc-

tive cycles of the various species. In the present

study, observations were made on reproductive

cycles and on environmental conditions in three

locations over a 3 to 4 year period, in order to

determine the extent to which there has been a

separation in the timing of reproductive events in

these closely related species, and to elucidate

possible factors controlling the reproductive

cycles.

The most northerly ranging of the species in

the present study is Mopalia ciliata, which is

known from Unalaska Island in the Aleutians

(Dall, 1921; M wosnessenkii = M. ciliata) to

Bahia Totos Santos, Baja California (Berry, 1922),

and Mopalia muscosa, which is known from the

Shumagin Islands on the Alaskan Peninsula

(Dall, 1878; M. ciliata = M. muscosa) to Isla

Cedros, Bahia California (Berry, 1922). The other

40 THE NAUTILUS

April 30, 1980

Vol. 94 (2)

species range from southern Alaska southward.

Mopalia hindsii is the most southerly ranging

species, being reported from Sitka, Alaska, to the

Gulf of California (Dall, 1921). Mopalia lignusa is

known from Sitka to Bahia Magdalena, Baja

California (Dall, 1921). Mopalia laeinor has a

more restricted range, being reported only from

Sitka (Burghardt and Burghardt, 1969) to its type

locality at Olympia, Puget Sound (Pilsbry. 1918),

and more recently to central California (Rice,

1971).

On the British Columbia coast the different

species vary in their vertical distributions (Him-

melman, unpublished). Mopalia muscosa is an in-

tertidal species and occurs in greatest numbers in

the mid-intertidal region. Mopalia hindsii and

Mopalia ciliata are common in the subtidal com-

munity, as well as in the low intertidal zone, up

to the level of about 2 m above lowest water of

spring tides (LWST). M. ciliata is more often

found in tight crevices and under rubble than M.

hindsii, and in the intertidal area both species

are most common on vertical faces and under-

cuts. In contrast to the above species, Mopalia

laeinor is a subtidal species and rarely occurs

above LWST. Mtrpalia lignosa is most common at

126'

shallow depths in the subtidal zone, and in the

intertidal zone it can occur up to as high as 3 m

above LWST. It can be very common intertidally

in some quiet water places where there is much

organic debris (I. M. Cowan, personal communica-

tion).

STUDY AREAS AND METHODS

Most of the observations in the present study

were made at three locations in British Colum-

bia: in subtidal communities at First Narrows in

Vancouver and at Porteau in Howe Sound, and

in an intertidal community at Botanical Beach,

on the outer coast of Vancouver Island (Fig. 1). A

few collections were also made at Eagle Harbour,

11 km from First Narrows. Not all five species of

Mopalia were present in sufficient quantities for

regular collections at each site, and thus were

collected only where it was feasible to make

subsequent collections. I tried to collect 10 or

more adult animals of each species on each collec-

tion date, but this was often not possible for the

rarer species.

The gonadal index, defined as the percentage

wet weight of the gonad to total live body weight,

was determined for each animal, this providing a

FIG. 1. Southwestern British Columbia, shovnng where the animais and environmental data were collected.

Vol. 94 (2)

April 30. 1980

THE NAUTILUS 41

16 T

12-

X

C

nj

c

O

O

0

Mopalia hindsii

First Narrows

7

j "^Botanical Beach

12 10

First Narrows ^

1/

H 1 1 1 ) 1 1 1 1 1-

Botanical Beach

FMAMJJAS

1974

AMJ J ASONDJ FMAMJ J

1972 I 1973

FIG. 2. Moiwlia hindsii. Mean gonadal index and 95% confidence limits for animals at Fitsl Narrows and Botanical Beach. The

iiumherassmated u-ith each bar is the sample size.

Personal communication.). A good record of

temperatures at Porteau during the spawning

period in 1973 was made with a thermograph

at the collection site.

quantitative value for its reproductive condition.

In the process of determining the gonadal index, I

made a standard practice of returning the

animals to fresh sea water after allowing them to

dry on paper towelling for 15 min for weighing

purposes. When spawning was imminent in the

field, this procedure sometimes induced spavm-

ing. A record was kept of animals which spawned

in this manner. The weight range of the animals

used for plots of the mean gonadal index against

time was 10-35 g for Mopalia hindsii, 4-20 g for

M. ciliata. 8-35 g for M. laevwr, 4-19 g for M.

lignosa, and 10-50 g for M. m^iscosa. Gonadal in-

dices within these ranges are relatively indepen-

dent of animal size (Himmelman, 1976).

To examine the relationship between tempera-

ture and reproductive events, for the population

at First Narrows I used measurements of

incoming water at the Vancouver Public Aquar-

ium. Tlie intake was located 1 km from and at

about the same depth as the collection site, and

provides a good record of the conditions to which

the animals were exposed (a graph of these data

is presented by Himmelman, 1976). For the

populations at Botanical Beach, I interpolated

values from daily surface temperature measure-

ments taken at lighthouses at Sherringham and

Amphitrite Points (Fig. 1; Hollister, 1971, 1972,

1974, Giovando and Hollister, 1974; Giovando,

RESULTS AND DISCUSSION

Reproductive Cycles

Mopalia hindsii A distinctly annual reproduc-

tive cycle was seen in both locations where M.

hindsii was studied. At Botanical Beach, spawn-

ing was completed by mid-June 1972, since every

animal collected at this time had small gonads

containing few or no gametes (Fig. 2). During the

following summer, there was little gonadal

enlargement, but after September the gonads

grew rapidly to a peak in early April 1973. In

1973, there was a complete spawning during

April and all animals collected in May, June and

July 1973 had depleted gonads. In 1974, only four

collections were made. On 27 April, the animals

collected had partly spawned or spent gonads,

suggesting that spawning was near completion,

and all animals collected in May and June were

in spent condition.

At First Narrows, animals in the first collec-

tion in April 1972 had completed spawning (Fig.

2). Gonadal grovrth commenced in the spring and

by late August the gonads were two-thirds mac-

imum size. This was in marked contrast to the

42 THE NAUTILUS

April 30, 1980

Vol. 94 (2)

FIG. 3. Mopalia hindsii. Summary of spawning ubservations.

events at Botanical Beach, where gonadal growth

did not start until autumn. At First Narrows,

gonadal growth during the autumn and winter

was slower and a peak was reached in Januarj'

1973. Spawning at First Narrows in 1973 was a

slow process, lasting 2-3 months, in contrast to

the one month spawning at Botanical Beach in

that year. It was underway in early March, when

one spent animal and six with intermediate-sized

gonads were collected, and all animals did not

have spent gonads until 10 April. In 1974, M.

hindsii had an abrupt spawTiing at First Nar-

rows. A few partly spawned animals were first

collected on 4 April and spawning was completed

on 15 April. Gonadal growth during the summer

was again evident at First Narrows in 1974.

A list of spawning observations for M. hindsii

from the present and earlier studies is shown in

Figure 3. Barnawell (1954) observed a reproduc-

tive cycle in M. hindsii in San Francisco Bay

similar to that observed in my study. There was

a progressive increase in the proportion of

animals with large gonads from late August to

November 1952, and the majority of the animals

collected from January to April 1953 had large

gonads. Subsequently, spawning occurred, since

most animals collected in May had small gonads.

E^ release by M. hindsii from two locations in

Marin County, California, was seen during late

October by Thorpe (1962). In Monterey Bay, M.

hindsii showed gonadal growth starting in the

autumn in 1956, 1957 and 1958, and there was a

well defined spawning in March in 1956 and 1957,

but not in the following three years (Giese, 1959;

Giese et ai. 1959, Giese and Araki, 1962). A

gradual decline in the mean gonadal index oc-

curred from November 1957 to July 1958, and

three breeding periods were reported between

November 1959 and late spring 1960.

Mopalia ciliata

Botanical Beach

i 1 1 I — I 1 1 1 1 1 1 — I

MJJASONDJFMAMJ

1972 I 1973

FMAMJ J AS

1974

FIG. 4. Mopalia ciliata. Mean gonadal index and 95% confidence limits for animaU at F^rst Narrows and Botanical Beach.

Vol. 94 (2)

April 30, 1980

THE NAUTILUS 43

In summary. Mopalia hindsii shows gonadal

growth starting in the summer in the subtidal

population at First Narrows, and starting in the

autumn in intertidal populations at Botanical

Beach and Monterey Bay. There is usually

spawning in March or April, but in California in

some years there may be spawning activity from

early winter to late spring.

Mopalia ciliata. The reproductive cycle of M

ciliata was studied in greatest detail at First

Narrows (Fig. 4). The data from 1972 and 1973

showed a regular cycle, even though only a few

animals were found on some collection dates.

Gonadal enlargement in 1972 proceeded gradually

after June and reached a peak in January 1973.

All animals collected in March 1973 had mature

gonads, and one male in each of the two March

collections discharged some sperm, suggesting

that spawning was imminent. The gonadal in-

dices dropped abruptly in early April 1973 and

every animal from the 14 April collection had

depleted gonads.

In 1974, there may have been some summer

spawning following the main spring spawning.

All animals collected on 20 April and earlier had

mature gonads, and one-half of the animals col-

lected on 24 April had spent gonads. It was unex-

pected to find four of five animals from 7 May

with large mature gonads. Possibly spawning was

delayed in some localized areas at First Narrows,

and the variation in the data was due to sam-

pling error. Most of the animals collected in June

and July had mature gonadal tissues, but many

of these animals had small- to intermediate- sized

gonads. By 18 September, 10 of the 13 animals

collected had sj^ent gonads.

On 20 April 1971, two M. ciliata with depleted

gonads were collected at First Narrows. On the

assumption that this species is mature during the

winter, as in 1972 and 1973, spawning in 1971

probably occurred in March or April.

At Eagle Harbour, two collections of M. ciliiiln

were made near the time of the 1973 spawning

season. The mean gonadal index decreased from

11.8 ±1.9 (95% confidence interval, n = 10) on 23

March to 10.2±2.8 (n = 9) on 4 April, and all

animals in both samples contained large quan-

tities of gametes. Here, spawning may have oc-

curred at about the same time as at Fii"st Nar-

rows.

FIG. .5. Mopalia ciliata. Summary of spawning observations.

At Botanical Beach, four collections of M.

ciliata were made in 1974 (Fig. 4). On 27 April,

all animals collected had large mature gonads.

The mean gonadal index dropped abruptly during

May and all animals from June and July were in

spent condition.

A summary of spavming observations for

Mopalia ciliata is shown in Figure 5. In British

Columbia spawning occurred from late March

through May, except at First Narrows in 1974,

when there was some delayed spawning activity.

In San Francisco Bay, Barnawell (1954) reported

that animals with large gonads were found in all

seasons, but his data show a decrease in the pro-

portion of animals with large gonads from April

to July, which suggests there was spawning ac-

tivity during this period. From various locations

in California, Thorpe (1962) reported 20 observa-

tions of individuals spawning: 12 were in the

period 21 February to 21 March, one was from 15

July, and seven were in the period 25 September

to 20 November.

TTius, Mopalia ciliata spawns from late winter

through spring in British Columbia, but in the

southern part of its range it may also spavm in

the summer and autumn. The timing of gonadal

growth is only known for First Narrows, where it

starts in the summer.

Mopalia laeinor. This species was only ex-

amined in the subtidal populations at Porteau

and First Narrows (Fig. 6). At Porteau, spawning

was in progress, but near completion, when the

first collection was made on 8 April 1971. The

mean gonadal index was low, but four animals

released gametes in the laboratory. In 1972,

spawning was delayed, since all animals collected

on 7 April, with the exception of one partly

44 THE NAUTILUS

April 30, 1980

Vol. 94 (2)

FIG. 6. Mopal ia laevior. Mean gonadal index and 95% confidence limits for animals at First Narrows and Porteau.

spawned male, had large gonads. There was an

abrupt spawning at Porteau in 1973. On 27

March only one spent animal was collected, and

on 10 April all animals had nearly completed

spawning.

At First Narrows, there was no indication of

spawning in collections from March and April

1972, but one animal collected on 8 May was in

spent condition, as were all animals collected in

June and August (Fig. 6). The gonads enlarged

rapidly during the autumn of 1972 and reached

peak size by late January 1973. One animal with

a small gonad was found on 6 March and another

on 30 March. In the latter collection, four

animals spawned in response to being dried and

rewetted. There was an abrupt spawning in early

April 1973, and only small quantities of gametes

or none at all were seen in animals collected on

14 April. As in M. ciliata, the spawning period of

M. ku'inor at First Narrows in 1974 was poorly

defined. The mast .striking drop in the mean

gonadal index was during 10-24 April, but the

data were erratic and a high proportion of

unspawned animals was later collected on 30

April and 7 May. Animals collected on different

dates, and probably from slightly varied

localities, differed in the extent to which they

had spawned, suggesting that the population at

First Narrows did not spawn in synchrony in

1974. All animals from the 18 September 1974

collection had spent gonads.

One collection of M. laonor was made at Eagle

Harbour on 4 April 197.3. The mean gonadal in-

dex was 1.4±0.7 (n = .5) and all animals had

depleted gonads.

In summary, Mopalia laevior has a distinctly

annual reproductive cycle, with gonadal growth

starting in the autumn and usually an abrupt

spawning in the spring (Fig. 7). At First Nar-

rows, spawning always occurs in synchrony with

spawning in M. ciliata. TTiere are no data on

reproductive events in M. laevior in the

literature.

Mopalia lignosa. At Porteau, M. lifjnom ap-

peared to spawn twice in 1971 (Fig. 8). Spawning

was imminent on 8 April, when all animals had

large mature gonads and four males spawned in

the laboratory. One month later, seven of the 10

animals collected had intermediate- to small-sized

gonads. Subsequently some gonadal growth oc-

curred and there was additional spawning activi-

ty sometime between mid-June and late-August.

In 1972, one collection of four animals was made

on 7 April. TTiree males had gonadal indices of

1 5.-3- 19.5 and one female had an index of 7.5.

These four animals appeared mature, but could

not be induced to spawn in the laboratory. In

First Narrows

Eagle Harbour

FIG, 7, Miipalia \^e\mT. Summary of spautiing observations.

Vol. 94 (2)

April 30. 198n

THE NAUTILUS 45

A M J

J A S

1971

O N D J

F M A M J J A

1972

S O N D J

F M A

1973

FIG. 8. Mopalia lignosa. Mean gonadal index and 95% confidence limits for animals at Porteau, and gonadal index value for each

animal collected at First Narrows.

1973, animals with mature gonads were found in

February, and spawning occurred sometime prior

to 10 April, when the eight animals collected con-

tained only small quantities of gametes. The one

animal collected on 27 March 1973 was in spent

condition.

Interpretation of the reproductive cycle of M.

lignosa at First Narrows was complicated by both

the small size of many of the samples and the ir-

regular sequence of events (Fig. 8). In 1971,

spawning may have occurred in April, since one

animal from 20 April released sperm in the

laboratory. In 1972, three spent animals were

found in March. Animals with larger gonads were

found in April through June and some spawning

may have occurred in the summer, since in

August the animals collected contained smaller

quantities of gametes. There was no evidence of

spawning in November 1972 and January 1973,

but by late April 1973, the gonads were notably

smaller and contained only traces of gametes.

There are few data on spawning of M. lignosa

in the literature (Fig. 9). On the open coast near

San Francisco Bay, Thorpe (1962) observed

spawning by five animals between 27 February

and 13 March 1957. In a study during April and

May 1974, Watanabe and Cox (1975) induced

some animals to spawn in the laboratory by

keeping them in stale water. They were unable to

induce spawning by numerous other methods.

In summary, reproductive events in Mopalia

lignosa follow a less regular pattern than in M.

hindsii. M. ciliata and M laeinor. There can be

spawning during late winter, spring and summer,

and gonadal growth may occur in the spring as

well as in the winter.

Mopalia miiscosa. Midway in the study of M.

muscosa, I realized that the reproductive condi-

tion of animals varied greatly in different pools

at any one time. Since animals from different

pools on the same collection dates were not

FIG. 9. Mopalia lignosa. Summary ofspauming observations.

46 THE NAUTILUS

April 30, 1980

Vol. 94 (2)

12

10

8

§ 6

MopaIJa muscosa

Botanical Beach

0' — ' 1 H-

FMAMJ JASONDJFMAMJJASONDJFN/AMJ JASON

1971 I 1972 I 1973

FIG. 10. Mopalia muscosa. GinuuM index values for indii'idnah collected at Botanical Beach.

separated, mean gonadal indices were not

calculated. Figure 10 shows the gonadal index

value of each animal collected on 15 dates at

Btjtanical Beach during 1971 through 1973. At all

times in the year, mature and spent animals

were found and no peak period of reproductive

activity was evident. However, animals within

any one pool tended to have similar gonadal in-

dices. For example, on 4 August 1973, five

animals from a pool at 2.6 m above LWST had in-

dices ranging from 1.9-4.2, whereas five animals

Botanical Beach

Monterey Bay, Calif.

Puget Sound, Wash.

Corona del Mar, Calif.

San Francisco Bay

Santa Monica Bay:

Flat Rock

Sunset Point

Latigo Point

Monterey, Calif.

from a pool at 1.8 m had values of 5.0-8.6. To

determine seasonal trends in Mopalia mmcosa, it

would probably be necessary to make collections

throughout the year from a .specific pool which

contained enough animals to sustain this amount

of sampling.

There are reports of observed spawnings or of

gonadal index decreases in M. muscosa in all

seasons of the year (Fig. 11). EJarnawell (19.54)

found a high proportion of individuals with large

gonads throughout the year in San Francisco

Boolootian, 1964;

Monroe &

Boolootian, 1965

FIG. 11. Mopalia muscosa. Summary of Spawning observations.

Vol. 94 (2)

April 30, 1980

THE NAUTILUS 47

Bay. In Santa Monica Bay, California, Boolootian

(1964) and Boolootian and Monroe (1965) in-

dicated that in three different locations there

were major drops in the mean gonadal index dur-

ing the winter and spring, but their data also in-

dicate that animals with mature gametes were

present even when the mean gonadal index was

low.

In conclusion, in contrast to the other species,

in Mopcdia muscosa reproductive events are not

closely coordinated amongst animals in single

geographical locations. In any season, some

animals may be undergoing gonadal growth and

others may be spawning.

Control of Gonadal Growth

Thei-e are several patterns in the timing of

gonadal growth in the genus Mopalia. In Mopatin

ciiiata gonadal growth starts in the early

summer and continues until a peak is reached

in mid-winter. In contrast, in Mopalia laevior the

gonads remain small during the summer and

there is rapid gonadal development during the

autumn and early winter. Surprisingly, both pat-

terns occur in Mopalia hindsii: gonadal growth

starts in the summer in the subtidal population

at First Narrows, and in the autumn in the in-

tertidal populations at Botanical Beach and

Monterey Bay. These two patterns of gonadal

development are widespread in shallow water

marine invertebrates of temperate and polar seas.

For example, in concurrent studies in the same

study areas, gonadal growth started in the sum-

mer in the chitons, Tonicella lineata and

Tonicella insignis, and in the urchin,

Strongylocentrotiis droebachiensis (Himmelman,

1976). In the latter reference, I have already

discussed the possible environmental factors

which might be controlling these patterns. Brief-

ly, the initiation of gonadal growth in the sum-

mer may be influenced by high temperatures or

steadily decreasing photoperiod. Possibly ap-

propriate light sensitivities were shown by

laborator>' studies, in which I found significant

changes in the rate of movement of the Mopalias

in response to small changes in light intensity

(Himmelman, unpublished). The initiation of

gonadal growth in the autumn may be stimulated

by lowered or steadily declining temperatures.

The latter changes could also be important in the

coordination of intermediate gametogenic events,

such as vitellogenesis, in the species which begin

gametogenesis in the summer. The final matura-

tion phase of gametogenesis could be stimulated

by minimal annual temperatui-es, the change to

increasing temperatures, or the rapid change

from decreasing to increasing photoperiod. These

considerations are, of course, speculative and the

actual factors will not be elucidated until ex-

periments, in which one factor is varied at a

time, are performed.

The data on gonadal grovrth in Mopalia lignosa

is less clear. There appears to be gonadal growth

following spawning periods in late-winter to

early-spring, as well as in the autumn after sum-

mer spawning activity. There is no obvious

widespread environmental factor that is cor-

related with both these periods of gonadal

growth. Possible gonadal grovrth is stimulated by

some local factor, such as food availability.

Control of Spawning

Spawning times vary in different Mopalia

species and only M. ciiiata and M. laevior, which

spawn together in the spring, show the same pat-

tern. Temperature is most frequently considered

to govern spawning in marine invertebrates. At

First Narrows in the present study, the late

April spawning of M. laeuior in 1972 and the ear-

ly April spawning in 1973 can be related to

temperature, since both spawnings occurred when

temperatures reached 7.6°C. However,

temperatures at First Narrows were similar in

the spring of 1973 and 1974, and thus

temperature differences would not account for

the abrupt spawning of M. laevior and M. ciiiata

in 1973 compared to the poorly defined spawnings

in 1974 (Fig. 4. 6). In 1974, sea temperatures when

M. ciiiata spawned were warmer at Botanical

Beach (about 9°C) than at First Narrows. The

Botanical Beach population was in the intertidal

zone, and therefore subjected to more varying

temperatures than the subtidal population at

First Narrows. At Porteau, a thermogi'aph at the

collection site showed only a slow increase from

7.5 to 8.3°C during the two week period when M.

laevior spawned. Thus, it is apparent that the

relationship between temperature and spawning

48 THE NAUTILUS

April 30, 1980

Vol. 94 (2)

in M. ciliata and M. laevwr varies in different

places and years.

In concurrent studies on other invertebrates,

including the chitons, Tonicella lineata and

Tonicelln insiyrm, and the urchin, StromjiiUicen-

tratui^ droehachiensui, I found similar inconsisten-

cies between temperature and spawning in the

field (Himmelman. 197f)). Also, attempts to induce

the above animals to spawn in the laboratory (us-

ing animals collected just prior to spawning in

the field) by exposing them to temperatures

warmer or colder than in the field, as well as to

sudden changes in temperature, were not suc-

cessful (Himmelman, 1975).

On the other hand, spawning in M. laevior. M.

ciliata, T. lineata, T. irmgnis and S. droebachien-

sis is closely correlated with the spring

phytoplankton bloom (Himmelman, 1975, 1976).

For example, the abrupt spawning of these

species at First Narrows and Porteau in 1973

coincided with a sudden outburet of diatoms. In

1974, the spring bloom was delayed and less well

defined, and this corresponded to the prolonged

and less well defined spawnings in that year.

Laboratory studies on T. lienata, T. insignia and

5. (Irorhnrhioiaia demonstrated that spawning

could, indeed, be induced by e.xposing ripe animals

to natural phytoplankton at approximately bloom

concentrations (Himmelman, 1975). There is no

experimental evidence that phytoplankton causes

spawning in M. ciliatu and M. laevior but the

coincidence is persuasive.

The cues for spawning in Mopalia lignom and

Mopalia hindsii are less clear. At Porteau in

1971, M. Uqnom appeared to spawn once in late

April and a second time in the summer, thus

under considerably different environmental con-

ditions. Also at F'irst Narrows, the three M.

lujnosa collected on 18 March 1972 were in sfx-nt

condition, suggesting that there has been spawn-

ing while temperatures were near the annual

minimum and prior to the spring phytoplankton

bloom. The data for 1973 are scant. One animal

collected at Porteau on 27 March, and two from

First Narrows on 30 March had depleted gonads,

suggesting that spawning in 1973 preceded the

bloom. Thus, neither temperature nor

phytoplankton appeal's to be imjx)rtant in the

spawning of Mopalia lignnm. and the actual

spawning stimulus remains elusive.

In the present study, Mopalia hiruLm had a

single annual spawning, but the timing of this

event preceded the spawning of M. riliatcu M.

laevior, and other species which spawn in syn-

chrony in the spring. At First Narrows, M. hind-

s-ii spawned in 1973 and 1974 during the period

when temperatures were near the annual

minimum, or just starting to increase. At

Botanical Beach, M himh-ii was in .spent condi-

tion before spawning was completed in M. ciliata,

T. lineata and the black leather chiton,

Kntharina tunicata (Himmelman, 1976). Collec-

tions at this location were not made frequently

enough to show whether the spawnings of M.

hindsii preceded those of S. droebnchiensis. Obser-

vations from earlier studies in Monterey Bay

(Fig. 3) can be compared to environmental data

for the same area (Bolin and Abbcjtt, 19(i3). As in

my study, there was a late winter spawning in

19.56 and 1957 coinciding with near minimal sea

temperatures. Surprisingly, the mean gonadal in-

dex showed a slow decline from November 1957

through spring 19.58. This unusual pattern may

be related to the unusually warm temperatures

in 1958. This was the warmest year in Monterey

Bay in a 40 year period and temperatures during

the winter of 1957-1958 were near normal sum-

mer levels. The spawning periods of M. hindsii in

Monterey Bay were not as,sociated with periods

of heavy phytoplankton abundance. In summary,

spawning in Mopalia hindsii is usually associated

with near minimum temperatures during late

winter, and is completed before the spring

ph\1oplank1on outburst.

In Mopalia nm.'^com reproductive events are

less coordinated, amongst animals in single loca-

tions, than in other species in the present study.

At Botanical Beach, seasonal trends in reproduc-

tive activity were not evident in the data from

animals collected from pools in various parts of

the mid-intertidal region. In an earlier study in

Santa Monica Bay, California, the mean gonadal

index followed an irregular pattern, although

some trends were suggested (Boolootian, 19(>1).

Tlie marked irregularity of reproductive events in

M. nniscoaa is probably related to its unique ver-

tical distribution. Unlike the other species, it is

re.stricted to the intertidal region, and at

B(Uanical Beach it was most abundant in pools at

1.8-3.0 m above LWST. The fact that animals

Vol. 94 (2)

April 30, 1980

THE NAUTILUS 49

from specific pools were in similar condition, hut

not animals from different {:k)o1s, suppest that

reproduction in this species is controlled by en-

vironmental conditions in the immediate vicinity

of the animals, therefore, by such factors as iX)ol

size, intertidal height, and food conditions.

Widespread environmental conditions, such as

temi)erature. photoperiod. and phytoplankton

abundance, appear to be less important in con-

trolling reproduction in M. muscosa.

ACKNOWLEDGMENTS

Early discussions on the indentification and

ecology of the Mopalias with Di'. Ian McTaggart

Cowan stimulated my interest in these animals. 1

am grateful to Drs. Helga Guderley, Tliomas

Carefoot and McTaggart Cowan for valuable com-

ments on the manuscript. Helga also contributed

with her unique ability at finding Mopalias at

Botanical Beach. Dr. Norman Wilimovsky was

generous in making the facilities at Botanical

Beach available to me. During this study, I was a

recepient of a National Research Council of

Canada scholarship, and was aided by a NRC

grant to T. Carefoot.

LITERATURE CITED

Barnawell, E. B. 1954. The biology of the genus Mopaliu in

San Francisco Bay. M. A. Thesis. University of California.

Berkeley.

Berry, S. S. 1922. Fossil chitons of western North America.

Proc. Calif. Acad. Sn. (ser. 4) ll:.399-526.

Bolin. R. L. and D. P. Abbott. 196.3. Studies on the marine

climate and phytoplankton of the central coastal area of

California, 1954-1960. Rep. Calif. Coiyp. Oceanic Pish. Invert.

9:23-45

Boolootian, R. A. 1964. On growth, feeding and reproduction

in the chiton Mopalia muscosa of Santa Monica Bay.

Helyiilander uiss. Meeresimters. 11:186-199.

Burghardt. G. E. and L. E. Burghardt. 1969. A collectors

guide to the west coast chitons. San Francisco Aquarium

Society. Special Publication No. 4:45 pp. -I- 4 pits.

Dall, W. H. 1878. Report on the limpets and chitons of the

Alaskan and Arctic regions, with descriptions of genera and

species believed to be new. Priic. U. S. Nal. Mus. 1:281-:M4

-f- 5 pits.

1921. Summary of the marine shellbearing

mollusks of the northwest coast of America, from .San

Diego. California, to the Polar Sea. mostly contained in the

collection of the United States National Museum, with il-

lustrations of hitherto unfigured species. Bull. U. S. Nat.

^Wm-s. 112:1-217 -I- 22 pits.

Giese, A. C. 19.59. Reproductive cycles of some west coast in-

vertebrates. In: Photoperiodism and related phenonema in

plants and animals. Amer. A.is. Adu. Set. Piil>i No. 55:

625-6:K K. H. Withrow, Ed.

Giese, A. C, J. S. Tucker and R. A. B(K)lootian. 19.59 Annual

reproductive cycles of the chitons, Kathanna tutiimtn and

Mopalia hindsil Biol. Bull. 117:81-88.

Giese, A. C. and G. Araki. 1962. Chemical changes with

reproductive activity of the chitons. Katharina lunicata and

Mopalia hindsii. J. Exp. Ziml. 151:2.59-267.

Giovando, L. F. and H. J. Hollister. 1974 Observations of

seawater temperature and salinity at British Columbia

shore stations. 197.'3. Environment Canada, Pacific Marine

Sciem-e Report 74-11:1-107.

Hewatt. W. G. 19:38. Notes on the breeding seasons of the

rocky beach fauna of Monterey Bay, California. Proc. Calif.

Acail. Sci (ser. 4) 23:283-288.

Himmelman, J. H. 1975. Phytoplankton as a stimulus for

spawning in three marine invertebrates. J. Erp. Mar. Biol.

&o^ 20:199-214.

1976. Factors regulating the reproductive cycles

iif some west coast invertebrates. Ph. D. Tlicsis. University

of British Columbia, Vancouver.

Hollister, H. J. 1971. Observations of seawater temperature

and salinity at British Columbia shore stations. 1970. Fish.

Res. Bd. Canada Manuscript Report Series 1156:l-i:i3.

1972. Observations of seawater temperature and

salinity at British Columbia shore stations. 1971. Marine

Science Directorate, Pacific Region, Pacific Marine Science

Report. 72-14:1-123.

1974. Observations of seawater temperature and

salinity at British Columbia shore stations. 1972. Environ-

ment Canada. Pacific Marine Science Report 74-1: 1-105.

MacGinitie, G. E. and N. MacGinitie. 1968. Natural Histoiy of

Marine Animals. 2nd. Ed., McGraw-Hill, N. Y. .523 pp.

Monroe, H. C. and R. A. Boolootian. 196.5. Reproductive

biology of the chiton Mopalia muscosa. Bull. South. Calif.

Acad.Sci. 64:223-228.

Pilsbry, H. A. 1918. Descriptions of new species of Mopalia

and Ti'achudermon. Tlie Nautdiis 31:125-127.

Rice, T. 1971. Marine ShelL^ of the Pacific Northwest. Ellison

Industires. Inc., Edmonds, Washington. 102 pp.

Ricketts, E. F. and .J. Calvin. 1966. Between Pacific Tides. 3rd.

Ed. Sranford University Press. Stanford. 516 pp.

Thorpe, S. R. 1962. A preliminary report on spawning and

related phenomena in California chitons. The Veliiirr

4:202-210.

Watanabe, J. M. and L. R. Cox. 1975. Spawning behavior and

larval development in Mopalia lignosa and Mopalia muscosa

(Mollusca; Polyplacophora) in central California. The

VcH9er(Suppl.) 18: 18-27.

50 THE NAUTILUS

April 30, 1980

Vol. 94 (2)

GONIOBASIS VIRGINICA (GASTROPODA: PLEUROCERIDAE) IN THE

CONNECTICUT RIVER

Douglas G. Smith

Museum of Zoology

University of Massachusetts

Amherst, Massachusetts 01003

ABSTRACT

TTie Connecticut River in New England is the northeastern range limit of the

pleurocerid snail Goniobasis virginica (Gmelin) where smooth shells predominate

over spirally Urate shells, while color-banding is present only on younger

specimens. Individual occur only in areas where shallow rocky reefs are

developed. Oviposition probably commences in spring and continues through to at

least July. Range contraction over the last 80 years is believed to be the result of

pollution, especially downstream where high water temperature and pH create

adverse conditions.

The Virginia river snail, Goniobasis virginica

(Gmelin, 1791), although well-known to 19th cen-

tury naturalists as an inhabitant of large Atlan-

tic coast rivers, was not reported from the Con-

necticut River until the 20th century (Pilsbry,

1892; Winkley, 1901). Subsequent to these papers,

a number of small collections were made of this

species in the Connecticut River which eventually

were transferred to the Museum of Comparative

Zoology, Harvard University. Thereafter, the

lower Connecticut River was considered to be the

northeastern terminus of the total range of G.

virginica (Goodrich, 1942).

Like most major rivers in the United States,

the Connecticut River has been subjected to

various forms of pollution as well as dam con-

struction. Each has resulted in the general

degradation of the quality of the river's water.

The removal of a magnificent salmon, shad and

sturgeon fishery, chiefly through the erection of

dams, was well-documented by the 19th century

(Netboy, 1968). However, little information has

appeared regarding the fate of lesser esteemed

organisms in the Connecticut River, particularly

the benthic invertebrates.

The fortunate existence of early voucher collec-

tions of (i. ifirginica from the Connecticut River

in the Museum of Comparative Zoology has per-

mitted an assessment of the present status of the

snail in the Connecticut River. The present paper

attempts to provide some data on the present

distribution and population structure of G.

virginica in the Connecticut River as well as in-

formation regarding the snail's biology.

METHODS AND MATERIALS

To establish a permanent record of the con-

tinued presence of G. virginica in the Connecticut

River collections were made from August, 1978,

to June, 1979, in areas known to be inhabited by

this snail. Specimens were narcotized in mentho-

lated water, fixed in a 10% formalin solution and

stored in 70% alcohol. The collections (UMA Nos.

MO. 1065, 1105, 1107) have been deposited in the

Museum of Zoology, University of Massachusetts

at Amherst. Conchological material from the

same areas has been deposited in the Museum of

Comparative Zoology, Harvard University and

the American Museum of Natural History, New

York. Existing collections of G. virginica from the

Connecticut River were analyzed for historical

distributional information and for range deter-

minations. Measurements taken on all specimens

included only aperture height as shell height and

width were affected by erosion. However, five of

the largest specimens were measured for total

length to determine maximum shell size.

Live material was retained in a ten gallon

aquarium to monitor activity. Specimens were

successfully maintained for five weeks after

which they were released. Supplementing field

collections, water analyses at two stations, Suf-

field and Warehouse Point, Connecticut, were

performed on June 18, 1979, when the river level

Vol. 94 (2)

April 30, 1980

THE NAUTILUS 51

was low. Free carbon dioxide (CO2), DO and pH

were determined in the field using a Hach CA-10

portable water chemistry kit. Additionally, water

samples were brought to laboratory facilities at

the University of Massachusetts. Total hardness

was ascertained by use of a Hach HA-4P hard-

ness kit while pH was checked for accuracy by a

calibrated Fisher Accumet pH meter. Individual

chemical analyses, including diagnosis of the

presence of heavy metals, were performed by the

Environmental Quality Engineering Facility,

Water Analysis Laboratory, University of

Massachusetts. Also, to estimate population den-

sity, meter square (M^) grids were established at

Suffield and Warehouse Point, Connecticut, on

June 18, 1979. Three grids ranging from .005 to

.650 meter in depth were sampled at Warehouse

Point while two grids ranging from .000 to .350

meter in depth were sampled at Suffield.

Finally, 14 specimens, collected on 24 June,

1979, were preserved in 10% formalin and serial-

ly sectioned for determination of gonadal activity.

Individual gonids were sectioned at eight

microns, dehydrated in an alcohol series and

stained with Delafield's hematoxylin and eosin or

fast green. Five slides were prepared for each

specimen.

RESULTS AND DISCUSSION

Biology

Goniobasis virginica often expresses two shell

morphologies, a smooth form and a Urate form,

the latter historically given the nomen

"multilineata" (Tryon, 1873). Pilsbry (1892)

observed both forms in the Connecticut River.

Presently a lirate phenotype is found among Con-

necticut River shells of G. virginica, however, the

characteristically raised lines are best developed

only younger specimens with an aperture height

of about seven millimeters. Larger specimens

usually have recognizably raised spiral lines con-

fined to the lower third of the body whorl.

Among a large sample of dead shells, lirate forms

comprised 17 percent of the total sample (122

specimens). Pilsbry (1892) further noted that Con-

necticut River specimens of this species were

large. Harman and Berg (1971) gave maximum

lengths of 27.5 to 31.0 mm (aperture height, 9.0 to

11.0 mm) for material they collected in New

York. Recent Connecticut River animals are com-

paratively larger, ranging from 30.8 to 32.5 mm

total length (five largest specimens, X = 31.3

mm) and have aperture heights of 11.4 to 12.2

mm.

External color markings are subdued on recent

Connecticut River snails. Younger specimens (to

seven millimeters aperture height) often display

a single chestnut color band on only the body

whorl. Larger adults show no banding. Museum

specimens collected around 1900 from the Connec-

ticut River often show two similarly colored

parallel bands on the lower portion of the shell of

younger specimens.

Recognition of size classes and identification of

cohort structure was not possible due to complete

overlap of variously aged specimens. Dazo (1965),

summarizing the available data on egg laying

cycles in Goniobasis spp., showed that the season

generally begins in early spring and lasts through

the summer. The only reference specifically deal-

ing with G. inrginiea (Winsor, 1933) cites egg lay-

ing as occurring in June in Maryland. Connec-

ticut River G. virginica probably lays eggs from

spring to July. Histological inspection of the

gonads of 14 specimens showed that by June,

males were spent and females only occasionally

contained eggs in the ovary. Captive females held

in an aquarium continued to lay small clutches of

one to four eggs through July.

Harman (1972) has characterized G. virginica

as a slow current, "clean cobble" inhabiting

species. The present study supports Harman's

diagnosis as this snail predominantly favors firm,

clean substrates in the Connecticut River. The re-

maining micro-populations of G. virginica in the

Connecticut River are found only in areas where

the current continuously washes lithic surfaces.

Animals are totally absent from intervening silt

covered embayments and beaches. The three

localities surveyed supporting aggregations of G.

virginica were unique in that the accretion of

rocks and gravel, brought about by both natural

and artificial factors, has resulted in a "funnel-

ing" effect, thus concentrating river flow over

reduced area. One site is a rocky delta that was

built up at the mouth of a stream.

The other two sites exist underneath highway

bridges, where residual land fill combined with

accumulated rock debris has created a shoal be-

tween the shoreline and the nearest bridge sup-

port. Reefing in the above localities intensifies

the river's current and, hence, increases abrasion

52 THE NAUTILUS

April 30, 1980

Vol. 94 (2)

FIG. 1. An adult specimen of Goniobasis virginica from the

Connecticut River fX 1.5). Note algal growth on shell

of the rock surfaces thereby providing a clean

substrate for habituation by snails.

Individuals of G. virginica in the Connecticut

River host a number of epizootics and parasites.

Dense growths of algae (Fig. 1) adorn the shells

of older specimens. Occasionally thick colonies of

the Entoproct (Bryozoan) UmateUa gracilis Leidy

also cover the shell of some specimens. Internally,

rediae and sporocysts of an undetermined species

of trematode are sometimes found in high num-

bers in reproductive tissues (Fig. 2).

^

,7--W^

FIG. 2. Photomiciiyiaph nj a sttiiun Ihiuiu/h the mcera of a

specimen of G. virginica ^X 100). GN-Gonadal tissue, SP-

sporocyKts ofparasit ic I re mat ode.

Spnngfiald

N

ma.

ct.

^ R*cord«. 1Ma-cs tOOO

\J No apcctmana loc*t«d;

I97S- lero

9 Known populolton:

1978- 1079.

FIG. 3. Map of the Connecticut River in southern New

England showing former and present distribution of G.

virginica. Shaded area indicates portion of river affected by

the salt wedge.

Distribution

Based on collections existing in the Museum of

Comparative Zoology at Harvard University, sup-

plemented by a few specific references (Pilsbry,

1892; Winkley, 1901), G. inrginica. at the turn of

the century, occupied a 60-mile range within the

Connecticut River. Recent search, however, has

revealed that G. virginica presently survives in

only a five mile stretch of the river between the

Enfield-Suffield area and Warehouse Point, Con-

necticut (Fig. 3). Massengill (1976) did not repwrt

it from Haddam, Connecticut, well within the

species historical range.

Since the early collections were made after the

larger dams were built, it is likely that the range

contraction experienced by G. mrginica resulted

from deterioration of water quality, although the

form of pollution responsible is unknown. Har-

man and Berg (1971) listed comparatively narrow

Vol. 94 (2)

April 30, 1980

THE NAUTILUS 53

ranges of typical chemical characteristics in

which G. inrginica was found in New York, sug-

gesting that G. inrginica is intolerant of "dirty"

conditions. Water analyses were performed at

two sites on the Connecticut River on a day when

stressful conditions would be most apparent due

to very low water level and high atmospheric

temperature (25C). The first site at Suffield, Con-

necticut, suggested conditions comparable to

those in which G. inrginica is found in New York

(Harman and Berg. 1971) (Table 1). However, the

second site, Warehouse Point, revealed high pH

and water temperature (Table 1). Other para-

meters were within expected limits although

dissolved oxygen was high. Warehouse Point is

the farthest dovrastream G. virginica occurs in

the Connecticut River and is where the species

shows the greatest biological difficulty. Quali-

tative sampling during May at Warehouse Point

when water conditions were more ameliorable

turned up only seven living specimens. Quan-

titative sampling later in June, using M^ grids,

produced no living animals, an indication of

worsening conditions. The suffield cite contained

291 and 433 individuals per M' at two grids

respectively. Graphic analysis of survivorship of

adult animals utilizing aperture heights, was per-

formed for two micro-populations, Suffield and

Warehouse Point (Fig. 4). The contrast between

curves A and C is produced in part by differences

in sample size and shell size. Whereas curve A

was derived from an adequately large sample

(62 specimens) Curve C was generated by the

only seven living specimens collected. Curve B,

representing museum specimens collected around

TABLE 1. Chemical characteristics of environments support-

irig populations of G. virginica. All concentrations in parts

per million (ppm). D0= dissolved oxygen, CaCO, = hardness

as calcium carbonate. Cft = free carbon dioxide.

e 8 10 12

Apertuf* h«lght(mm)

FIG. 4. Distribution of shell -mes. based on aperture heights,

of specimens in three collections ofG. virginica /ro/T! the Con-

necticut Ri^'er: (A) Suffield, Ct.. recent: (B) Springfield. Ma.

to Hartford, Ct, about 1900; (C) Warehouse Point. Ct.. recent.

Curves were fitted to a scatter plots which can be furnished

upon request.

1900 between Hartford, Connecticut and Spring-

field, Massachusetts, is also representative of a

small sample (10 specimens) and is included only

for comparative purposes. Despite the conditions

alluded to above, it is evident that Suffield snails

are as large as, or larger than, snails found at the

beginning of the present century in similar

localities. Warehouse Point snails, however, do

not achieve the same sizes of the other samples

suggesting that, at Warehouse Point, either

growth is curtailed or death preceeds maximum

development.

Additional chemical analyses were performed

on Warehouse Point and Suffield water samples

in hopes to pinpoint the cause of mortality

among G. virginica at Warehouse Point.

Although heavy metal content was low, both sites

showed high ammonia (NH3) levels (.10 ppm, Suf-

field; .14 ppm. Warehouse Point). Alone these

values do not answer why differential survival

rates exist at each site, however, the high water

tem'perature and alkalinity at Warehouse Point,

the source of which is unknown, may enhance

ammonia toxicity (Hynes, 1960; Harman, 1974).

During warmer months, toxic ammonia probably

eliminates those specimens that gain a foot hold

at Warehouse Point during cooler periods.

The future holds an uncertain prognosis for the

continued existence of G. virginica in the Connec-

ticut River. Dispersal by snails, either up or

downstream is controlled by the snail's ability to

find suitable substrate to establish self-sustaining

M THE NAUTILUS

April 30, 1980

Vol. 94 (2)

populations as found at Suffield and Enfield.

Furthermore, downstream movement, which

would seem the direction of least resistance, is

blocked by adverse water conditions as

demonstrated at Warehouse Point. Although the

surviving pockets of snails at Enfield and Suffield

appear healthy, inability to disperse combined

with short term fluctuations of water levels,

caused by human activity, which periodically

strand large numbers of snails out of water, place

excessive pressure on a few reduced gene pools to

maintain sufficient viability and adaptability to

ensure the species survival in the Connecticut

River.

ACKNOWLEDGMENTS

I should like to thank William Nutting,

Richard Johnson, Diane Romeo, Eugenia Zavras,

Richard Gillerman and Stuart Ludlam for their

assistance during the preparation of this

manuscript. Financial assistance was provided in

part by a grant from the Connecticut River

Watershed Council.

LITERATURE CITED

Dazo, B. C. 196.5. The morphology and natural history of

Pleuroca unita and (iariinhnsi,'; livescens (Gastropoda;

Cerithiacea: Pleuroceridae). Mducolugia 3(l):l-80.

Goodrich, C. 1942. The pleuroceridae of the Atlantic Coastal

Plain. Mu.seum Zoology. University Michigan. Orrasionnl

/'fipr/>-4.')6:l-fi.

Harman. W. N. 1972. Benthic .substrates their effect on fresh-

water MoUusca. EcoLigy 53(2): 271-277.

. 1974. Snails (MoUu.sca: Gastropoda) In: Pdllutinn

ErnUtgy of Freshwater Invertebrates. Editors: C. W. Hart,

.Jr. and S. L. H. Fuller. Academic Press, Inc., New York, pp.

27.5-312.

Harman, W. N. and C. 0. Berg. 1971. The freshwater snails of

Central New York. N.Y. State Agric. Exper. Sta.. Search:

Entomology 1(4): 1-68.

Hynes, H. B. N. 1960. TTip Biology of PoUrUed Waters. Univer-

sity of Toronto Press, Toronto. 2f)2 pp.

Ma.ssengill, R. R. 1976. Benthic fauna: 196.5-1967 versus

1968-1972. In: The Connecticut River Ecological Study, Eds.

D. Merriman and L. M. Thorpe. Americdii fisheries Sorie-

ty. Monograph l:.39-.53.

Netboy. A. 1968. The Atlantic Salmon. Houghton Mifflin Co.,

Boston. 4.57 pp.

Pilsbry. H. A. 1892. Goniobasis virginica in Connecticut. The

Nnutihiis6C3y.3&.

Tryon. G. W. 1873. Land and Freshwater Shells of North

America. Part IV. Strepomatidae (American Melanians).

Smithsonian Institution, Smithsonian Miscellaneous Collec-

tions 253:l-ii5.

Winkley, H. W. 1901. Goniobasis in Massachusetts. TTie

Nautihts 15{lY.m.

Winsor. C. P. 1933. The eggs of Goniobasis virginica Gmelin

and Anculosa carinata Brugiere. Journal Washington

Academy Science 9:243-259.

MICROSTRUCTURE OF THE CRYSTALLINE STYLE OF

SPISULA SOLIDISSIMA (BIVALVIA: MACTRIDAE)>

Harlan K. Dean

112 Pollution-Ecology Laboratory

College of Marine Studies

University of Delaware

Lewes, Delaware 19958

ABSTRACT

A method of fixation is introdueed which allows light and scanning electron

microscopy to be used in the stwdy of the molluscan digestive style iLsing the

bivalve, Spisula solidissima Dillwyn. Energy dispersive x^ray analyse of this style

supports the hypothesis of internal liquification of older style material.

The crystalline style is a relatively large

mucoid rod present in several prosobranch gas-

tropods and in all bivalves save the protobranchs

(Purchon, 1968). This structure occupies the style

'University of Delaware College of Marine Studies Contribu-

tion No. 78101

sac which is completely separate in some species

and continuous for all or part of its length with

the midgut in others. The anterior end of the

style projects into the stomach cavity and the en-

tire structure is believed to be rotated by the

cilia of the epithelium lining the style sac. Rub-

Vol. 94 (2)

April 30, 1980

THE NAUTILUS 55

bing of the stomach epithelium by the style tip is

avoided by the presence of a protective gastric

shield.

The style is approximately 80% water and is

composed mainly of mucoproteins (Bailey and

Warboys, 1960; Doyle, 1966). Bailey and Warboys

(1960) found that although 67% of the dry weight

of the style of Pinna mobilis was protein, much

of this protein was associated with carbo-

hydrates; there were only negligible amounts of

enzymatic proteins. The most common sugars

making up the carbohydrate fraction are hex-

osamine, galactose, and fucose (Hashimoto and

Sato. 1955; Bailey and Warboys, 1960; Doyle,

1966).

Mechanical functions attributed to the style in-

clude the stirring of stomach contents, trituration

of particles against the gastric shield, retrieval of

food from the midgut and coating of abrasive

particles with mucous (Bernard,. 1973). Physio-

logical functions include use as a source of

digestive enzymes and as a buffering agent (Ber-

nard, 1973).

The enzymes reported present in style material

are primarily carbohydrases (Kristensen, 1972;

Wojtowicz, 1972). Most commonly present are

amylase (Bailey and Warboys, 1960; Mathers,

1973; Langton and Gabbott, 1974) and laminarase

(Sova et ai. 1970; Wojtowicz, 1972). Shallenberger

et ai (1974) found laminarase to be the major

style enzyme in Spisula solidissma. Other

enzymes reported from bivalve styles are lipase

(Mathers, 1973), maltase, and cellulase (Kris-

tensen, 1972).

Study of the structure and mechanical function

of the crystalline style has been hampered by its

transitory nature. Morton (1970) and later

Langton and Gabbott (1974) reported that many

bivalves dissolve their styles during low tide and

reform them at high tide. Kristensen (1972)

demonstrated that formation of style material

occurred only when animals were actively

feeding. Yonge (1923) noted that the styles of

bivalves possessing a separate style sac and

midgut were always present and fairly persis-

tant. Those bivalves whose style sac and midgut

communicate were often found to lack a style or

to possess one which dissolves rapidly upon

removal from the style sac.

Because of the high water content of the style

and its transitory nature few techniques for

rigorous examination of its structure have been

demonstrated. Some work using transmission

electron microscopy has been accomplished

through standard plastic embedding techniques

(Wourms, 1970; Ghiselin, de Man, and Wourms,

1975).

This paper describes for the first time a

method of fixation of crystalline styles which

allows its examination by light or scanning elec-

tron microscopy. Due to the large size and high

stability after dissection, the style of the clam,

Spisula mlidissima Dillwyn, (family: Mactridae)

was used to demonstrate this method. This

species has a gastropemptan stomach (type V ac-

cording to the classification of Purchon (I960))

with a completely separated sac and midgut.

METHODS

Styles were collected from specimens of Spuula

solidissima maintained in a running seawater

table. Valves were cracked open and a lateral in-

cision made into the stomach cavity. Styles were

fixed in 10% Sorenson's phosphate buffered for-

malin with a small amount of acetic acid (0.06 ml

acetic acid per 10 ml formalin) for approximately

24 hours. Dehydration was carried out by 8-12

hour changes in 30%, 50%, 70%, 85%, and 95%

ethanol at 0°C. The material was then slowly

warmed to room temperature and transferred to

absolute ethanol. Transfer from 70% to 85%

resulted in approximately twenty percent

shrinkage. After dehydration, styles were

critical-point dried (a Denton DCP-1) and

mounted on stubs. Specimens to be viewed with

the scanning electron microscope were coated

with carbon and gold and viewed with a Cam-

bridge Stereoscan Mark H and a Phillips SEM-

501. Portions of styles used for elemental

analysis were coated with carbon and examined

qualitatively by energy dispersive x-ray analysis.

RESULTS

The style of SpKula solidvarimn possesses an

extended anterior tip and is drawn out to an

elongate point posteriorly (Fig. 1). The major

length of the style is composed of numerous con-

centric longitudinally oriented lamellae. When

viewed with light microscopy these lamellae sur-

round an inner core of granular material. In a

56 THE NAUTILUS

April 30, 1980

Vol. 94 (2)

^ ?

FIG. 1. Drawing of the crystalline style o/Spisula solidissima. Scale bar equals 1 cm. A - anterior tip of the style. B -food bolus, C -

head of the style. D - cotuitricted zone. E - lamellae of the style. F- central core of granular material.

scanning electron microscopy this granular

material seemed to be very similar to the

lamellar material (Fig. 2). Elemental analysis of

these two zones by energy dispersive x-ray

analysis also indicated that these two zones are

identical in composition with reference to the two

major elements detected, calcium and sulphur.

The constricted area posterior to the bulbous

head of the style lacks a core of granular

material. Under the light microscope this con-

stricted zone possesses several rings on the ex-

terior surface. These are similar to the impres-

sions noted by Kristensen (1972) in styles of

Macoma balthica (Linn^). Scanning electron

microscopy revealed that these rings actually con-

sist of terraced layers of exterior lamellae (Fig. 3

and 4).

The bulbous head of the style is composed

mainly of granular material with only a few

lamellae present at the exterior surface. The nar-

row anterior tip extends from the head of the

style and is pressed against the gastric shield at

the left anterior wall of the stomach. This portion

of the style is also composed of terraced lamellae

similar to those of the constricted area (Fig. 5).

Much of this tip is surrounded by a food bolus of

amorphous material interspersed with occasional

diatoms (Fig. 6).

DISCUSSION

The style had been thought to be secreted in

the posterior end of the style sac replacing

material lost to dissolution in the stomach. Using

in vivo staining on styles of Macoma balthica and

Abra nitida of European seas Kristensen (1972)

found that new style material is added along the

entire length of the style sac. This discovery was

later substantiated by Bernard (1973) by labeling

the style with barium. On the basis of his stain-

ing experiments Kristensen hypothesized that

older style material moves inward to the central

axis of the style, undergoes liquification and col-

lapse, and is then forced anteriorly toward the

stomach.

Examination of the structure of the style of

Spii^ula .s'o/rrfmiwa tends to support the

hypothesis of internal collapse and liquification

of old style material described by Kristensen

(1972). Both the lamellar and granular style

material were similar in composition in respect

to the two elements detected with energy disper-

sive x-ray analysis. Material from both regions of

the style was also quite similar in appearance,

although the granular material seemed more

loosely organized. The similarity of these two

regions also tends to refute independent secretion

of lamellar and granular material hypothesized

by Alexander and Rae (1974).

The present study suggests that formation of

the style occurs entirely within the style sac.

Rings described by Kristensen (1973, Fig. 1) on

the collar of the style of Macoma balthica are

similar in appearance to the terraced lamellae

found on the style of Spisula solidissima (Fig. 3

and 4). The edge of each ring represents the effec-

tive anterior limit of the style sac during secre-

tion of each lamella. This suggests that the style

decreases in diameter and is shifted incremental-

ly in an anterior direction prior to the laying

down of new lamellae in the style sac.

The lack of f(X)d material on the exterior sur-

face of the style of Spisula solidvisima fails to

support Bernard's (1973) hypothesis that the style

sac epithelium is a digestive surface. Histo-

chemical studies by Mathers (1973) of Ostrea

pdidis and Cmssostrea ang}tlata have demon-

strated that the style sac epithelium does not

show reactions typical of an area of absorption

while the stomach and midgut epithelium do.

Evidently the major portion of the style sac

Vol. 94 (2)

April 30, 1980

THE NAUTILUS 57

FIG. 2-6. Scanning electron micrographs of the crystalline style uf Spisula solidissima. 2, Cross section at the approximate

midlength of the style. Scale bar equals 100 urn. CC - central core of granular material, L - lamellae. 3, Exterior surface at the con-

stricted area of the style. Scale bar eqiuds 50 urn. TL - teiraced lamella. 4, Longitudinal section of the constricted area of the style.

Scale bar equals lOO urn. TL - terraced lamella. 5, Anterior tip of the style imth the encircling food bolus paiiially removed. Scale

bar equals 50 urn. A - anterior tip of the style. 6, Teiraced organization of the lamellae at the anterior tip. Scale bar equals 100

um.

epithelium function mainly in ciliary rotation

and forward movement of the crystalline style.

In addition to the style of Spisula solidissima

that of the Mahogany Clam, Arctica islandica

(Linne) was also fixed successfully in the present

study using this same procedure. This success

suggests that this method may be employed with

a wide range of gastropod and bivalve species to

compare styles from a broad range of stomach

and feeding types. Changes in style morphology

during tidal cycles and in response to varying en-

vironmental factors, subjects of considerable cur-

58 THE NAUTILUS

April 30, 1980

Vol. 94 (2)

rent interest (Reid and Reid, 1969; Morton, 1970;

Kristensen, 1972; Bernard, 1973; Lanpton and

Gabbott, 1974), can also be explored with this

method.

ACKNOWLEDGMENTS

All phases of this study benefited greatly from

the direction and aid generously provided by Dr.

Melbourne R. Carriker, College of Marine

Studies, University of Delaware. Specimens of

Spisula solidissima were kindly provided by Ms.

Mary Gibbons also of the College of Marine

Studies. Preliminary examination with scanning

electron microscopy was made with Ms. Takako

Nagasi on a Cambridge Stereoscan Mark II in the

Department of Geology, University of Delaware.

A Phillips SEM-501 was used for final examina-

tion in the Department of Mechanical Engineer-

ing, University of Delaware with the aid of

Mr.Walter Denny. I am indebted to these people

for their help during this work.

This research was supported in part by an In-

dustrial Partners grant from the University of

Delaware's College of Marine Studies.

LITERATURE CITED

Alexander, C. G. and J. C. Rae. 1974. The structure and for-

mation of the crystalline style of Telescnphim telescopiuni

(Linnaeus), l/c/ii/cr 17:56-60.

Bailey. K. and B. D. Warboys. UMjO. The Lamellibranch

crystalline style. Biochem. Jour. 76:487-491.

Bernard, F. R. 1973. Crystalline style formation and function

in the oyster Crfutsostrea gigas (Thunberg, 179.5). Ophelia

12:159-170.

Doyle, J. 1966. Studies on the chemical nature of the

crystalline style. In H. Barnes (ed.): Some contemporary

sUtdies in Marine Scieiice. pp. 2.5'?-26.3. G. Allen and Unwin

Ltd.. London.

Ghiselin, M. T. E. de Man, and J. P. Wourms. 1975. An

anomalous style in the gut of Megatebennus bimaculatus. a

carnivorous prosobranch gastropod. Veliger 18:40-43.

Hashimoto. Y. and T. Sato. 19.5.5. Studies on the crystalline

style of molluscs. II Chemical constitutents of the style of

Mai-tm siilcatarin Reeve (Part 2). Bull. Jap. Sue. Seient.

Fish. 21:a52-356.

Kristensen, J. H. 1972. Structure and function of crystalline

styles of bivalves. Op/ie/iVi 10:91-108.

Langton, R. W. and P. A. Gabbott. 1974. The tidal rhythm of

extracellular digestion and the response to feeding in

Ostrea edidis. Marine fljofoj 1/24:181-187.

Mathers, N. F. 1973. A comparative histochemical survey of

enzymes associated in Ostrea edulix and Crassostrea

angnlutn (Mollusca: Bivalvia). Jour Zooi. London 169:

169-179.

Morton, B. 1970. The tidal rhythm and rhythm of feeding

and digestion in Cardium edule. Jour. Mar. Bio. Ass. U. K.

50:499-512.

Purchon, R. D. 1960. The stomach in the eulamellibranchis;

stomach types IV and V. Proc. ZooL Soc. London

135:431-489.

. 1968. The Biology of the Molhisca. Pergamon

Press, N. Y. 225-243.

Reid, R. G. B. and A. Reid. 1969. Feeding processes of

members of the genus Macoma (Mollusca: Bivalvia). Can.

Jour Zool. 47:649-6.57.

Shallenberger, R. S., C. Searles, and B. A. Lewis. 1974.

Laminaranase activity in the crystalline style of the surf

clam (Spissula [sic] soUdisstma). Experientia 15:597-598.

Sova. V. v.. L. A. Elyakova. and V. E. Vasdovsky. 1970. The

distribution of laminarinases in marine invertebrates.

Comp Biochem. Physiol. 32:4.59-464.

Wojtowicz. M. B. 1972. Carbohydrases of the digestive gland

and the crystalline style of the Atlantic deep-sea scallop

(Placopecten magellanicus, Gmelin). Comp. Biochem.

Phyml 32:131-141.

Wourms, J. P. 1970. Towards a characterization of the ex-

tracellular tubular components of the moUuscan crystalline

style. Journal o.fCell Etiology 47:232a.

Yonge, C. M. 1923. Studies on the comparative physiolog>' of

digestion. The mechanism of feeding digestion, and

assimilation in the lamellibranch Mya. Brit. Jour. Eip.

fiio/. 1:15-63.

A NEW PREPARATION FOR OBTAINING

CHROMOSOME SMEARS IN HYDROBIA

(HYDROBIIDAE)

R. N. Howard, B. Z. Lang, and R. L. Carr

Department of Biology

Eastern Washington University

Cheney, Washington 99004

Hydrobia sp., probably hemphilli (Pilsbry,

1933), is found in numerous cold springs of

eastern Washington. Comparative morphological,

ecological, and cytogenetic studies have been in-

itiated on selected populations of this snail to

determine what biological variations occur within

its eastern Washington range. This report is con-

cerned with a new technique for obtaining

chromosome spreads from Hydrobia.

Few techniques have been described for obtain-

ing chromosome spreads in snails. Burch (1968)

treated tissue-cultured ovatestes cells with a col-

chicine solution and demonstrated metaphase

chromosome spreads in land snails. Babrakzai

Vol. 94 (2)

April 30, 1980

THE NAUTILUS 59

and Miller (1974) used a similar colchicine squash

technique on pulmonale land snails. Patterson

(1971) treated freshwater embryos with an iso-

tonic velban solution and demonstrated mitotic

metaphase chromosome spreads. Stern (1974) used

a similar velban technique on snails of the family

Oleacinidae. The success of these techniques re-

quires complex equipment and lengthy pro-

cedures. The method described in this paper re-

quires little apparatus and is completed with

minimal time and effort. The technique described

has been applied only to Hydrobia sp. but may

have application in other molluscan groups.

Large numbers of Hydrobia sp. were collected

from five populations in eastern Washington. A

small hole was made in the second body whorl of

the shell using a small probe. This was to allow

passage of a micropipette into the body mass of

the snail. The snails were injected with 2.67 ul of

10"' colchicine using a Prior England

micropipette injection system and placed in

finger bowls containing distilled water for two

hours. The shell of the snail was gently crushed

and the gonads removed, placed on a glass slide

and stained in 1 percent iron-aceto-carmine for

seven minutes. The tissue was completely covered

with the stain. A coverslip was added and gently

tapped with a metal forceps to effect spreading of

the tissue. Excess stain was removed with a

paper towel and the slide was placed between

two sheets of paper toweling and slowly com-

pressed by thumb pressure.

Figure 1 shows metaphase chromosomes of

Hydrobia sp. (2n = 36). Chromosome spreads be-

tween the various populations were numerically

identical. Spermatogenesis occurred in all popula-

tions during the summer months. One population,

sampled through November, showed an apparent

increase in spermatogonia! activity. Egg produc-

tion was initiated in October in this population.

Representative shells of Hydrobia sp. are showi

in Figure 2.

LITERATURE CITED

Babrakzai, N. and W. B. Miller. 1974. A colchicine hypotonic

squash technique for chromozome spreads of pulmonale

land snails. Malucol. Rev. 7:.37-38.

Burch, J. B. 1968. A tissue culture technique for karyotjise

analysis of pulmonate land snails. Vettiis 27:20-27.

FIG. 1. Mtt<ii)lM.st: chiiiinu.siitni sjjreud nj Hydri/bia sp. Scdle

line = 25 micra.

FIG. 2. Shells of Kydroh'vd sp. Smle line = 1 mm.

Patterson, C. M. 1971. A karyotj-pe technique using

freshwater snail embryos. Malacol. Rei: 4:27.

Pilsbry. H. A. 1933. Amnicolidae from Wyoming and Oregon.

The Nautilus i7:9-l2.

Stem. E. M. 1974. The chromosome number of Euglandina

rosea (Stylommatophora: Oleacinidae). The Nautilus

88:29-30.

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60 THE NAUTILUS

April 30, 1980

Vol. 94 (2)

SNAILS FROM QUATERNARY VALLEY FILL AT

CHACO CANYON, NEW MEXICO

Stephen A. Hall

Department of Geography

North Texas State University

Denton, Texas 76203

ABSTRACT

Nine species of land and aquatic snaih occur in prehistoric alluvium at Chcuco

Canyon, New Mexico. Shells o/Stagnicola cockerelli in the main valley fill indicate

the presence of intermittent pools on the undissected canyon floor during Basket-

maker and Puebloan occupation. Erosion of the post-Bonito channel eliminated the

aquatic snails by destroying their habitats. The drift snail fauna reported by

Drake (19Jt8) may be reworked from the prehistoric alluvium.

In northwestern New Mexico the Chaco River

has cut an SO-meter deep canyon through thick-

bedded sandstone. The canyon is called Chaco

Canyon, probably a Spanish variant of Navajo

words and an old name which was in use before

American contact (McNitt, 1964). During the late

Quaternary, Chaco Canyon was filled with thick

deposits of mud, sand, and gravel of which over 6

meters are now exposed in the banks of the

Chaco River arroyo. In the 1920's, during the Na-

tional Geographical Society's excavation of

Pueblo Bonito, one of the large number of aban-

doned pueblos for which Chaco Canyon was

named a national monument. Kirk Bryan investi-

gated the geology of the alluvial valley fill and

reported the occurrence of snail shells, including

an aquatic form now known to be Stagnicola

cockerelli (Pilsbry) (see Bryan, 1954). Later, dur-

ing archeological surveys and excavations at

Chaco in 1946 and 1947 by the University of New

Mexico, a major effort was made to document the

modem molluscan fauna (Drake, 1948). Although

no living snails were discovered, shells of fifteen

species and subspecies of land and freshwater

forms were found in drift, around ruins, on ant-

hills, and around seeps and springs in the sand-

stone cliffs.

During 1972 and 1973 the valley fill at Chaco

Canyon was again investigated, this time to

refine and radiocarbon date the stratigraphy

reported by Bryan and to analyze the pollen con-

tent of the alluvium (Hall, 1977). During inspec-

tion of the arroyo walls twelve localities were

discovered that yielded a total of 289 fossil shells

of land and freshwater snails. Shells were

recovered from each of the alluvial units des-

cribed from Chaco Canyon. The units are Fajada

(late Pleistocene), Gallo (about 7,000 to 2,400

years ago), Chaco (2,200 to 850 years ago), Post-

Bonito (600 years ago to 1860 A.D.), and Historic

(1935 to present). Details of these stratigraphic

units are presented elsewhere (Hall, 1977). The

snail species are listed in Table 1 by alluvial unit

and by numbers of individuals recovered.

Most of the shells found in the canyon fill are

from the Chaco unit, probably because it is the

principal fill unit in the canyon and more of it is

exposed in arroyo walls. The most abundant shell,

and the only form found in all five units, is a

succineid, probably Succinea. Drake (1948) iden-

tified S. ymsvenorii from Chaco Canyon, and the

fossil succineid shells are probably the same

form. Other abundant terrestrial species are

Pupoides hordaceus (Fig. 1), VaUonia cycU)-

phorella, and Hawaiia minuscula. Two freshwater

snails were recovered from the canyon fill:

Stagnicola cockerelli (Fig. 1) and Gyraidus sp.

Drake (1948) reported G. circumstriatus from

Chaco Canyon. However, the single fossil

Gyraidus shell recovered from the Chaco unit is

broken and cannot be identified to species.

Overall, seven of the eleven land forms and two

of the four freshwater forms reported by Drake

were recovered as fossils from the alluvium.

Paleoecology

The deposition of the main valley fill (Chaco

unit of Hall, 1977) coincides with the Basket-

Vol. 94 (2)

April 30, 1980

THE NAUTILUS 61

TABLE 1. Fossil ami living gastropods from Chaco Canyon, New Mexico.

' The species listed by Drake (1948) are duplicated here without alteration except for Stagnicola bidimoides cockerelli.

Mn general, identifications of the family Succineidae are reliable only through anatomical studies of the animal itself; shells alone

are of little value for species determination (Taylor. 1960. p. 77; Patterson, 1971).

maker and Puebloan occupation of the area be-

tween about 600 and 1200 A.D. and, accordingly,

the environmental reconstruction of the alluvium

applies to the prehistoric human ecology of Chaco

Canyon. The presence of aquatic snails and the

FIG. 1 (left) Stagnicola cockerelli /rom Chaco unit alluvium, 7.2

mm in height: (right) Pupoides hordaceus from Chaco unit

alluvium. 3.5 mm in height: .shells not to same scale.

impressions of rushes in the main valley fill were

cited by Bryan (1954, p. 50-51) as evidence for

more moist climate at Chaco Canyon. Bryan also

pointed out that the aquatic shells were found in

the post-Bonito channel fill as well (Post-Bonito

unit of Hall, 1977) but concluded that the

evidence for environmental conditions during the

time of prehistoric occupation was sparse.

A pollen analytical study of the Chaco Canyon

valley fill suggests that the pinyon (Pinus edulis)

and ponderosa (P. ponderosa) pine forests in the

region were less abundant during Basketmaker-

Puebloan occupation of the canyon than today

and that, accordingly, the climate was drier then

than it is today (Hall, 1977). A question that

arises is: how does a drier climate reconcile with

the occurrence of the aquatic snail Stagnicola

cockerellil The explanation probably lies with the

geomorphology of the canyon floor. During the

prehistoric occupation of the canyon and the

deposition of the Chaco unit, a deep arroyo chan-

nel such as exists today was not present. Sedi-

mentary structures in the Chaco unit indicates

that runoff from storms spread over the valley

62 THE NAUTILUS

April 30, 1980

Vol, 94 (2)

floor, perhaps in a network of shallow channels

no deeper than 20 to 30 cm. Due to the imper-

viousness of the clayey Chaco alluvium (Judd,

1964, p. 230-231) it is likely that water collected

in intermittent pools after each heavy rainstorm

and formed a suitable habitat for S. cockerelli.

This species ranges throughout the region today

(A. B. Leonard, 1959; Pilsbry and Ferriss, 1906;

Bequaert and Miller, 1973) where it has been col-

lected from ponds and ditches that are seasonally

dr>' (A. E. Leonard, 1943; Henderson, 1924). With

the trenching of the canyon floor by the post-

Bonito channel, the intermittent pool habitats

were eliminated. Subsequent filling of the old ar-

royo channel may have reestablished conditions

favorable for S cockerelli. The few fossils of S.

cockerelli in the later alluvium (Post-Bonito unit)

may reflect the presence of another series of in-

termittent pools or the shells may be reworked

from the older Chaco unit. At present a 10-meter

deep arroyo channel bisects the floor of Chaco

Canyon, and two summers of field work (1972

and 1973) produced no evidence of S. cockerelli or

any other species alive there today.

The Chaco Canyon snail record illustrates the

paleoecologic principle that snails, although ex-

cellent indicators of microhabitats, may be

misleading as guides to regional climatic condi-

tions. The record at Chaco Canyon suggests that

Stagnicola cockerelli and perhaps the other

aquatic species could inhabit the canyon floor as

long as intermittent pools were present. When

the canyon was trenched by the post-Bon ito chan-

nel, the pools and the snails were eliminated. The

fX)llen sequence indicates the climate became wet-

ter during the post-Bonito channel cutting. The

destruction of the aquatic snail's microhabitat,

however, resulted in the elimination of the

aquatic species from the canyon regardless

whether the climate became wetter or drier. The

presence of S. cockerelli in the Chaco unit

alluvium means only that water was available in

intermittent pools and does not necessarily mean

that the climate was more moist then than it is

now.

observed living snails at Chaco Canyon. TTiere is

a strong possibility that at least some and

perhaps all of the shells Drake collected from

drift were fossil shells eroded from the pre-

historic alluvium. The shells collected from ant-

hills could also be fossil, each one removed by

ants during nest excavation into deeply buried

alluvium and transported to the surface mound

along with small gravels. Although shells found

around seeps and springs in the cliffs could also

be fossil, they are more likely recent. Drake does

not mention which specimens were collected from

the springs and which came from drift.

Modern Fauna

The writer discovered three possible colonies of

a succineid, probably Siiccinea, and apparently

the same species that occurs as a fossil in the

canyon fill. The shells, all dead and bleached by

the sun, occur loose in surface duff at topo-

graphically depressed places that are periodically

inundated by runoff. The sites are (1) in Gallo

Wash canyon just north of the Camf)ground

(center sec. 22, T. 21 N., R. 10 W.), (2) in a small

area of the abandoned canyon floor northwest of

the U. S. National Park Service Visitor Center

(NW '/4 sec. 20, T. 21 N., R. 10 W.), and (3) in a

small mud flat covered by sunflowers south of

South Gap about 2 miles beyond the monument

boundar\' (center sec. 27, t" 21 N., R. 11 W.).

Isolated succineid shells also occur commonly in

the present-day dry floor of Chaco River arroyo.

ACKNOWLEDGMENTS

I thank Richard Hardin, Superintendent of

Chaco Canyon National Mounument during the

1972 field season, and Walter P. Herriman,

Superintendent during the 1973 season, for their

permission to work within monument boundaries.

I also thank Karoly Kutasi, Museum of Paleon-

tology, University of Michigan, who assisted with

photographing the shells and Carolyn Smith for

typing the manuscript.

Fossils Reworked in Drift

Nine of the twelve species reported by Drake

(1948) occur as well-preserved fossils in canyon

fill (Table 1). Neither Drake nor this writer

LITERATURE CITED

Bequaert. J. C. and Miller, W. B. 1973. The Molliisks of the

Arid Sduthwest with an Arizona Checklist. Tucson, Univ. of

Arizona Press, 271 p.

Vol. 94 (2)

April 30, 1980

THE NAUTILUS 63

Bryan. K. 1954. The geology of Chaco Canyon, New Mexico, in

relation to the life and remains of the prehistoric peoples at

Pueblo Bomto. Smithsonian Misc. Colin. 122(7):l-65.

Drake, R. J. 1948. Mollusca of the eastern basin of the Chaco

River, New Mexico. The Nautilus 62:5-8.

Hall, S. A. 1977. Late Quaternary sedimentation and

paleoecologic history of Chaco Canyon, New Mexico. (!poI.

Sx. Amer. Bull. 88:1593-1618.

Henderson, Junius. 1924. Mollusca of Colorado, Utah, Mon-

tana. Idaho, and Wyoming. The Univ. of Colorado Studies

13(2): 65-223.

Judd, N. M. 1964. The architecture of Pueblo Bonito. Smithso-

nian Misc. Colin. 147(l):l-349.

Leonard, A. B. 1959. Handbook of gastropods in Kansas. Univ.

of Kansas, Museum Natural History. Misc. Pnbl. no. 20, 224

P-

Leonard, A. E. 1943. The Mcjllusca of Meade and Clark coun-

ties, Kansas. Trans. Kans(u< Acad. Sci. 46:226-240.

McNitt, F. 1964. Navaho expedition. Journal of a military

reconnaissance from Santa Fe, New Mexico, to the Navaho

country made in 181,9 by Lieutenant James H. Simpson.

Norman, Univ. of Oklahoma Press, 296 p.

Patterson, C. M. 1971. Taxonomic -studies of the land snail

family Succineidae. Malacological Review 4: 131-202.

Pilsbry, H. A. and Ferriss. J. H. 1906. Mollusca of the

Southwestern states. IL Proc. Acad. Natural Sciences of

Philadelphia 5S:l23-n5.

Taylor, D. S. 1960. Late Cenozoic molluscan faunas from the

High Plains. U. S. Geol. Survey Professional Paper 337, 94

P-

DRILLING PREDATION ON SOME MIOCENE MARINE MOLLUSKS

Elizabeth C. Dudley

Department of Z(iology

University of Maryland

College Park, Maryland 20742

and

E. Christopher Dudley

Queen Anne School

Upper Marlboro

Maryland 20870

ABSTRACT

Drilling rates and stereotypy of drill hole position were examined on two

bivalves and a gastropod from a middle Miocene assemblage in Maryland. The

bivalves. Anadara elevata Conrad and Astarte thisphila Glenn, show a reduction in

predation rate mth an increase in size. The gastropod. Turritella plebeia Say. does

not appear to attain a size refuge against drilling. These results coirelate well

mth other reports of drilling predation throughout the fossil record.

The record of drilling by predatory snails and

other organisms is often clearly preserved in

fossil material. Paleozoic mollusks and brach-

iopods occasionally have drill holes which have

been attributed to molluscan predators (Fenton

and Fenton. 1931: Bucher. 1938; Cameron 1967).

It is now generally agreed, however, that the.se

holes were caused by non-molluscan borers

(Fischer, 1962, 1966; Carriker and Yochelson,

1968), and that mollusks did not develop the bor-

ing habit to an appreciable degree until mid- to

late-Cretaceous times with the appearance of the

naticid subfamily Polinicinae and the muricacean

genus M///fp.s(Sohl. 1969).

By the early Tertiary, drilling by naticids and

muricids (as well as by other organisms such as

octopods) had become quite widespread. A num-

ber of authors have described the drilling they

obser\'ed in various fossil assemblages. See, for

e.xample; Fischer (1962, 1966), Siler (1965), Taylor

(1970), and Adegoke and Tevesz (1974) for Eocene

assemblages; Hoffman et al. (1974), Kojumdjieva

(1974), and Thomas (1976) for Miocene assem-

blies; Thomas (1976), and Robba and Ostinelli

(1975) for the Pliocene; and Berg and Nishenko

(1975) for the Pleistocene.

As far as we can determine, with the probable

exception of Taylor's 1970 discussion of drilling in

an assemblage from the Paris basin, the above

authors examined materials from previously

sorted collections, rather than starting with the

fossil material in situ in the surrounding

64 THE NAUTILUS

April 30. 1980

Vol. 94 (2)

substrate. This paper reports on drilling in prey

species that were sorted from a single large block

of substrate in an attempt to eliminate any bias

arising from collecting techniques (such as the

discarding of broken shells, for example). Also, as

shown by Kojumdjieva's (1974) extensive data on

a Bulgarian Miocene formation, drilling frequen-

cy can vary considerably in local populations of a

prey species. Such variance can be obscured in

museum collections. We feel that our data on

three carefully sorted species accurately reflect

the predation rates sustained by the local popu-

lations.

MATERIALS AND METHODS

In the autumn of 1976 a very large cliff fall

occurred near St. Leonards, Calvert County,

Maryland, U.S.A., in the famous middle Miocene

outcroppings knovra as Calvert Cliffs. (See Clark

et al. (1904) for a complete review of these

deposits.) The authors were present the day of

the cliff fall, and determined that it came from

Zone 17 of the Choptank formation. This is an ex-

ceptionally fossiliferous zone, consisting of a

yellowish sand substrate embedded with an abun-

dant and diverse fauna.

Our analysis was carried out on an eighteen

kg. section from this fall. The material was

allowed to air dry for two months, and then in-

dividual shells were carefully removed. Most

gastropods and many bivalves did not fossilize

sufficiently well to be useful for the analysis.

However, three sf)ecies fossilized well, and we

sorted out all the specimens. Two bivalves and

one gastropod were used: Anodara elevata Con-

rad, Astmie thisphiln Glenn, and Tumtella

plebeia Say. Each specimen was measured to the

nearest millimeter with Vernier calipers. The

species were then divided into size classes, and

drilling frequency and position were examined.

For the bivalves, we made the assumption also

made by other workers, that the drilling frequen-

cy in a population is double that observed on

disarticulated valves.

The borers involved in this study were of the

family Naticidae. The Muricidae are known from

other formations in these Miocene beds, but are

extremely rare in the Choptank formation: we

did not see any in our sample. The most abun-

dant naticid was Lunatia heron (Say), a very

common species in the Choptank. Also present,

though less abundant, was Neverita duplicata

(Say). Those drill holes that were well preserved

were of the truncated parabaloid nature charac-

teristic of naticids (Carriker and Yochelson,

1968).

RESULTS AND DISCUSSION

Drilling frequencies for each of the three

species are recorded in Table 1. It is immediately

evident that Anadara elevata and AMarte

thii^phila. the two bivalves, exhibit a similar

reduction in the rate of predation with an in-

crease in size, whereas Turritella pleheki has a

higher rate of predation at the larger sizes. The

bivalves have relatively thick shells at their lar-

ger sizes, whereas T. plebeia is always a thin and

delicate shell. This perhaps explains why this

species does not appear to attain a size refuge, at

least in this population.

The rates of predation observed for these three

species are similar to those reported for another

Miocene assemblage (lower Tortonian) from the

Korytnica clays of Poland (Hoffman et ai. 1974).

For Anadara diluvii (Lamarck) 7% of the 656

specimens were attacked, which is close to the 9%

obsen'ed in the larger size class of A. elevata

(Hoffman et al. do not give size classes). The

three Tumtella species listed, T. bademis Sacco,

T. hicarinata Eichwald and T. envnea Cossmann

had predation rates of 17%, 28%, and 25% respec-

tively. Other authors cited in our introduction

have found similar rates in Eocene material,

although rates have also been recorded as high as

6.W0 in Mesalia. a turritellid genus (Fischer.

1962).

A striking feature of the drilling in these shells

is the degree of stereotypy of borehole position

(Fig. 1). In Anadara elevata 100% of the sue-

Vol. 94 (2)

April 30, 1980

THE NAUTILUS 65

FIGS. 1-3. Chaixuieristic Miocene naticid drill holes ui 1, Astarte thisphila. 2, Anadara elevata,

find 3. Turritella plebeia.

cessfu! drill holes were central and high on the

umbo. Interestingly, two of the three incomplete

holes noted were on other parts of the valve. The

holes in Asta7ie thisphila exhibited a broader

scatter, but all were contained within the upper

one third of the valve. In neither of these species

was there any indication that one valve was

drilled preferentially over the other. The drill

holes were exactly evenly distributed between left

and right valves in Astarte thisphila. and in

Anadara elevata there was a very slight and not

significant preference for the right valve.

Tunitella plebeia also exhibited stereotypy in

drill hole position. 98% of the holes were in the

penultimate and third from last whorls, and 7.5%

of all holes were on the apertural side of the

shell.

Such stereotypy of drill hole position has been

reported on all through the Tertiary and into the

Recent. Fischer (1960) looked at 1,222 valves of

Pectunculus (now Glycymeris) pulinnatns Lk.

from the Lutetian of Grignon, and found most

holes to be in the central region of the shell. Sohl

(1969) found naticid borings preferentially located

in the umbonal area of Crassatellites undulata

Say, of the Miocene Yorktown formation; and

Kojumdjieva (1974) reported a similar location

for drill holes in Anadara diluvii. Thomas (1976),

looking at Glycymeris americana (Defrance),

reported a shift in preferred boring site from the

middle to late Miocene. Stump (1975) found very

localized borings in naticid gastropod prey of a

Mexican Pleistocene assemblage, and Berg and

Nishenko (1975) found stereotyped drilling by

both Pleistocene and Recent naticids.

Thus stereotypy of drill hole position seems to

be a common phenomenon, one that varies be-

tween species, and also at different times within

the same species. Most authors seem to agree that

this stereotypy reflects both prey size and shape,

and the behavior of the predator. However, Boet-

tger (1930) pointed out other factors to be con-

sidered. He found that the degree of stereotypy

was affected by both naticid density and the

depth of the substrate. Fewer predators and a

deeper layer of substrate resulted in lessened

stereotypy in his work, and these factors may

play a role in other cases as well.

In conclusion, the data given here form the

first report on drilling predation in moUusks

from the Choptank formation of Maryland. They

are in substantial agreement with much of the

data from other locations and times, indicating

that drilling rates and stereotypy of drill hole

position have been remarkably consistent at least

since the Eocene. Since local variations in drilling

rates have been documented in the literature, we

feel that it is most useful to analyze data from

material collected from a single location in the

table opposite.

ACKNOWLEDGMENTS

The authors wish to express their grateful

thanks to Geerat J. Vermeij for his considerable

66 THE NAUTILUS

April 30. 1980

Vol. 94 (2)

assistance, and their appreciation to Larry and

Connie Smith for making possible the collection

of the materials examined.

LITERATURE CITED

Adegoke. 0. S. and M. J. S. Tevesz. 1974. Gastropod predation

patterns in the Eocene of Nigeria. Lethaia 7:17-24.

Berg. C. J. Jr. and S. Nishenko. 1975. Stereot>T).v of predatory

boring behavior of Pleistocene naticid gastropods.

Paleobiology 1:258-260.

Boettger, C. R. 19:30. Die Lage der Bohrstelle beim Angriff der

Raubschnecken aus der Familie Naticidae. Zeitschrifi

H'kspn.sr/i. Z„(l 136; Heft ' .:454-463.

Bucher, W. H. 19:?8. A shell-boring gastropod in a Dalmanella

bed of upper Cincinnatian age. Amcr. Jour. Sci. 5th Series,

36:1-7.

Cameron. B. 1967. Oldest carnivorous gastropod borings, found

in Trentonian (Middle Ordovician) Brachiopods. ./. Paleon-

toloyijil{\Y.W-\50.

Carriker, M. R. and E. L. Yochelson. 1968. Recent gastropod

boreholes and Ordovician cylindrical borings. U. S. Geoi

Sum. Prof. Paper 593-8:1-26.

Clark, W. B., G. B. Shattuck and W. H. Dall. 1904. The

Miocene Deposits of Man/land. Maryland Geological Sun^ey.

543 pp. The .Johns Hopkins Press, Baltimore.

Fenton, C. L. and M. A. Fenton. 1931. Some snail borings of

Paleozoic age. .4wpn Mid. Nat. 12:.522-528.

Fischer, P. H. 1960. Action des gaste'ropodes perceurs sur un

MEETINGS

Symposia on feeding mechanisms of pre-

datory mollusks and on the functional mor-

phology of cephalopods, as well as field trips, an

auction of shell literature, and a cruise on the

Belle of Louisville will highlight the Annual

Meeting of the A. M. U., July 19-25, 1980. at

Lcjuisville, Kentucky. A cash prize will be

offered for the best student paper. For further

information write Dr. C. F. E. Roper, Division of

Mollusks, National Museum of Natural History,

Washington, DC 20560.

The Western Society of Malacologists will

meet (with the AAAS) at the University of Cali-

fornia at Davis, June 23-25, 1980. Pre-registra-

tion forms, due May 23, are obtainable from Dr.

Vida C. Kenk, Dept. Biological Sciences. San

Jose State University, San Jose, CA 95192.

The Conchologists of America, an organiza-

tion mainly for amateur conchologists. will hold

their annual meetings in Key West, Florida,

August 6 through 9. 1980, with headquarters at

the Ca.sa Marina. This is three days after the

Jacksonville Shell Show. For further informa-

tion write Margaret Teskey. P.O. Box 273. Big

Pine Key, FL 33043.

bivalve de i'e'tage lutetian. Jour, de Conchyl. 100:129-131.

1962. Action des gasteropodes perceurs sur des

Mesalia de I'e'tage lutetien. Jour, de Conch yl. 102:95-98.

1966. Perforations de fossiles Tertiares par des

gaste'ropodes predateurs. Jour, de Conchyl. 105:66-96.

Hoffman, A.. A. Pisera and M. Ryszkiewicz. 1974. Predation

by muricid and naticid gastropods on the Lower Tortonian

mollusks from the Korytnica clays. Acta Geologica Polonica

24:249-260.

Kojumdjieva, E. 1974 Les Gaste'ropodes perceurs et leurs vic-

times du Miocene de Bulgarie du Nord-Ouest. Bulgarian

Acad. Sci.. Bull. Geol. Inst.. Ser Paleont. 13:5-24.

Robba. E. and F. Ostinelli. 197.5. .Studi Palecjecologici sul

Pliocene ligure I. Testimonianze di predazione sui molluschi

Pliocenici di Albenga. Rir. Itat. Paleont. 81:309-372.

Siler, W. L. 1965. Feeding habits of some ExK'ene carnivorous

gastropods. Texas Jour. Sci. 17:213-218.

Sohl, N. F. 1969. The fossil record of shell boring by snails

Am. ZooloyiKt 9:725-734.

Stump, T. E. 1975. Pleistocene mollustan paleoecolog>- and

community structure of the Puerto Libertad r^ion, Sonora.

Mexico. Palaeogeography, Palaeoclimatol.. Palaeoecol.

17:177-226.

Taylor. J. D. 1970. Feeding habits of predatory gastropods in a

Tertiaiy (Eocene) molluscan assemblage from the Paris

Basin. Palaeontology 13, part i254-260.

Thomas, R. D. K. 1976. Gastropod predation on sv-mpatric

Neogene species of Glycytneris (Bivalvia) from the eastern

United States. Jour. Paleont. 50:488-499.

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Vol. 94 (2)

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THE NAUTILUS 67

INVERTEBRATE FAUNULES OF LATE PLEISTOCENE AGE,

WITH ZOOGEOGRAPHIC IMPLICATIONS, FROM TURTLE BAY,

BAJA CALIFORNIA SUR, MEXICO

William K. Emerson

Department of Invertebrates

American Museum of Natural History

New York, New York 10024

ABSTRACT

Metazoan invertebrates representing 138 species, mostly mollnsks, are

enumerated and recorded quantitatively from six localities in ynarine terrace

deposits of the TwHle Bay region on the Pacific Coast of Baja California Sur, Mex-

ico. Faunules from two of the localities (B-302Jt and (B-3025) contain warmwater

(subtropical and tropical) elements and are refeyred to the late Pleistocene

Magdalean Province of western Baja California on the basis offaunal comparisons

unth regional assemblages. The two Turtle Bay assemblages with warmwater in-

dicators are probably correlative with an early phase of the Sangamon Interglacial

Stage (isotopic Substage 5e). More pi-ecise dating of the faunules from these

localities and reliable correlation of the four other faunules (localities B-3027.

B-30(i7. 8-33050. and B-30It8). which apparently lack warm-water elements, must

await absolute dating of the fossils.

This paper is dedicated to the memory of my esteemed colleague. Edwin C.

Allison (1926-1971), who collected the fossils in 1956.

Edwin C. Allison (1926-1971)

Introduction

Turtle Bay ' (Figure 1) is a small, protected em-

bajTiient on the southwestern side of the Vizcaino

Peninsula, Baja California Sur, Mexico (latitude

27° 41'N., longitude 114''52'W.: see Figure 1). In

the summer of 1956, the late Edwin C. Allison,

then of the Department of Geology, San Diego

State University, amassed large numbers of

Pleistocene marine invertebrates from several

highly fossiliferous terrace deposits in the vicini-

ty of Turtle Bay. Because of his primary interest

in the older rocks of the area (cf. Allison, 1957;

1964), he asked me to join him in co-authoring a

report on the terrace fossils of this paleon-

tologically poorly known region of western Baja

California Sur.

The identification of the megafossils was com-

pleted by me in 1960. Commitments to a heavy

teaching schedule and to other research projects,

however, prevented Dr. Allison from undertaking

the writing of the sections pertaining to the

' .Mso known as Bahia Tortugas (the port of which is called

San Bartolome or Puerto San Bartolome), and henceforth

cited as Turtle Bay.

68 THE NAUTILUS

April 30. 1980

Vol. 94 (2)

FIG. 1. Iwiex map of Baja Califnmia and the adjoining mainland nf Mexico and the United States, showing the general location

of Pleistocene localities (numbered 1-9) and the geographic localities representing the modem endpoint-s of range of some com-

ponents of the Turtle Bay Pleistocene faunules (see text).

Vol. 94 (2)

April 30, 1980

THE NAUTILUS 69

Table 1 . Pleistocene Faurral Lift, Turtle Boy

Symbols: F = frogmental preservotion; J = juvenile ipecimeni; M == many specimens; P= plate; PV = paired volves;

S = spine; V = single valves; x = presence of one or more specimens

Collecting Stations

Mollusca ^ g

Gastropoda A tt

Acanthina lugubris (Sowerby, 1822) -

Acteocino cf . A. corinota (Corpenter, 1857) - 1

Alio carinato (Hinds, 1844) - J

Anochis coronata forma honnana Hertlein and * -

Strong, 1951

Astroeo undoso (Wood, 1828)

Bittium quodrifilatum Corpenter, 1864

Bullo punctuloto A. Adorns, 1850

Bursa califomico (Hinds, 1843)

Coecum crebricinctum Carpenter, 1864

Caecum dolli Bartsch, 1920

Concellorio cassidiformis Sowerby , 1 832

Conthorus elegons (Griffith and Pidgeon, 1834)

Cerittilum moculosum Klener, 1841

Collisella llmotulo (Carpenter, 1864)

Columbello mojor Sowerby, 1832

Conus colifbmicus Hinds, 1844

Conus fergusoni Sowerby, 1873

Conus perplexus Sowerby, 1857

Conus purpura scens Sowerby, 1833

C6nus reguloris Sowerby , 1 833

Crepidulo onyx Sowerby , 1 824

Crucibulum scutel latum (Wood, 1828)

Cfucibulum spinosum (Sowerby, 1824)

Cypraeo onnettoe onnettae Doll, 1909

Cyproeo orobiculo (Lamarck, 1811)

IF

2F

2F

IF

IF

M

12

2

3

4

1

4

4

7

4F

7(1 THE NAUTILUS

April 30. 1980

Vol. 94 (2)

Cyprgeo spodicea Swainson, 1823

Diodoro digueH (Mobille, 1895)

Elephontulum corgenteri (Bortsch, 1920)

Eupleuro muricifofmii (Broderip. 1833)

Fortulum occidentale Borfsch, 1920

FisjureMo volcano Reeve, 1849

Haliotis fulgens Pt^tllppi, 1845

Hipponix gntiquofus (Linn^, 1767)

Hipponix fumens Carpenter, 1865

Homiospira moculoso (Sowerby, 1834)

KelleHo kellerii (Forbes, 1852)

LotHo gigontea (Sov/erby, 1834)

Mocron aefhiopi (Reeve, 1847)

Megasurcula carpenteriono (Gobb, 1865)

Mi fro idae Melville, 1893

Nossorius tegulo (Reeve, 1853)

Nerito scabricosta Lamarik, 1822

Neverito reclusiana (Deshoyes, 1839)

Norrisio norrisi (Sowerby, 1838)

Oliva incrassato Lightfoot, 1786

Oliva cf. O^. polpostg Dodos, 1833

Oliva polpasta forma davisae Durham, 1950

Oliva sp. indet.

Olivella biplicoto (Sowerby, 1825)

Pedipes cf . P. unisulcotus G>oper, 1866

Phyllonotus erythrostomus (Swoinson, 1831)

"Polinlces" sp. indef.

Pieudomelatomo penicillato (Gjrpenfer, 1865)

Pteroporpuro fesHvo (Hinds, 1844)

Seila cf. S. montereyensis Bortsch, 1907

3

5

3J

2

1

MF

IF

8

2F

R

o

2J

IF

3F

3

2

2

5

1

6

3

5

IJ

M X

2

2 22 X

M

1

2

2

4

IF

IF

11

IF

Vol. 94 (2)

April 30, 1980

THE NAUTILUS 71

Serpulorbis squamigerus (Corpenter, 1857)

StTombus graciliof Sowerby, 1825

Sfrombus granulahjs Swainson, 1822

Tegula aureotincta (Forbes, 1852)

Tegula eiseni Jordan, 1936

Tegula gollina (Forbes, 1852)

Teinostoma cf. T. gallegosi Jordan, 1936

Terebra armillato Hinds, 1844

Thais bi serial is (Blainville, 1832]

Triphoro cf. T^. pedroana (BarHch, 1907)

Trivia solondri (Sowerby , 1 832)

Trigonostoma goniostomo (Sowerby, 1832)

Truncgtellg californico Pfei ffer, 1 857

Turbcnillo sp. indef.

Turbo fluctuosus Wood , 1 828

Vitulorio salebrosa (Kingand Broderip, 1832)

Scaphopodo

Dentolium neohexagonum Sharp and Pilsbry, 1897

Bivolvia

Amiontis calloso (Ganrad, 1837)

Anomia peruviana d'Orbigny, 1846

Arcopsis solido (Sowerby, 1833)

Argopecten circularis circularis (Sowerby, 1835)

Barbotia gradotg (Broderip and Sowerby, 1829)

Borbofia reeveana (d'Orbigny, 1846)

Choceia ovoldeo (Gould, 1851)

Oioma sp. indet.

Chione calJforntensis (Broderip, 1835)

Chione cortezi (Gprpenter, 1864)

Chione gnidia (Broderip and Sowerby, 1829)

!

8

CO

8

o

2F

IF

6

3

1P\4 2V

IV

1 PV, 1 V

3V

IV

2V

4PV

IF

13

30

1

13

17

1

1

1

1

1

17

1FV

MV

14V

8PV

8V

I

O

S

IF

72 THE NAUTILUS April 30. 1980 Vol. 94 (2)

Cryptomyg colifofnica (ConrcxJ, 1837)

R

S

Oione pic>o Willed, 1944 - - - IV

Oione undotello (Sowerby, 1835) 2V - - -

Corbulo luteolo Girpenter, 1864 - 2V - 4V

Crossinello pocifico (C. B. Adorns, 1852) - - - 12V

8V - 2V

Diplodonto orbellus (Gould, 1851) - IV -

Donox colifomicus Conrad, 1837 - - - 1 PV

DosinJQ ponderosQ (Groy, 1838) - - - W

Epilucino califomico (Conrad, 1837) - IV

Felaniella sericoto (Reeve, 1850) _ . . 25V

Glons subquodrota (Carpenter, 1864) - 2V

Here excovoto (Carpenter, 1837)

Hinnites gigonteus (Groy, 1825)

Leporimetis obeso (Deshayes, 1855)

Lucinisco nottolii Conrad, 1837

Macomo indentato Carpenter, 1864

Mocomo nasuto (Conrad, 1837)

Macomo nasuto forma kelseyi Doll, 1900

Moctra cf. M. colifornica Conrad, 1837

Megopitoria squolido (Sowerby, 1835) - - .- 4y ^ - -

Milnerio minimo (Doll, 1871) - IV - - - - -

Mytilus cf . M. colifornionosConrod, 1837 - - - - - - ] py

Nuttallia nuttalii forma orcutti (Doll, 1921) - - IV - - - -

Ostrea angelica Rochebrune, 1895 . _ _ 23V x IV

Porvilucino opproximata (Doll, 1901) - IV - - - » _

Penitella fitchi Turner, 1955 . - - - _ ^^ _ _

Penitello penito (Conrod, 1837) IV IV -

Petricolo corditoides (Conrod, 1837) 2PV ------

Protothoco groto (Soy, 1831) 3V 2V - 15V x - 4V

Pseudochamo ponomensis (? formo dolli Bernard, 1976) - - - 2PV x - -

Vol. 94 (2)

April 30, 1980

THE NAUTILUS 73

Saxidomus nuttall] fConrod, 1837)

Semele deciso (Conrad, 1837)

Semele flavescens (Gould, 1851)

Togelus colifomianus (Conrad, 1837)

Tellina bodegensis Hinds, 1845

Tellinc simulons C. B. Adams, 1852

Tivela sKiltorum (Mawe, 1823)

Trochycardium ponomense (Sowerby, 1833)

Trochycardium quadragenorium (Conrod, 1837)

Transennella tantilla (Gould, 1853)

Tresus nuttolMi (Conrod, 1837)

Zirfoeo pllsbryi Lowe, 1931

8

7

3V

2V

6V

IFV

IV

2V

22V

2V

IV

4V

2JV

IPV

IV

IV

2PV,2V

2V

15V

O

IV

IFV

2FV

IV

IV

2FV

Polyplacophora

Stenoplox mogdalenensis (Hinds, 1845)

Bryozoa

Couloromphus spiniferum (Johnson, 1838)

Ganopeum commensoie Kiikpatriclc and Metzelaar, 1923

Logenipora punctulata (Gabb and Horn), 1862

Pgrosmining crosslondi (HosHngs, 1930)

Scrupocellaria bertholefti tenuirostris Osbum, 1950

TTialamoporelio califomiea (Levinsen, 1909)

Watersipora cucullato (Busk, 1854)

Echinodermata

Echinoidea

Dendrosfer vizcainoensis Grant and Hertlein, 1938

Eucidaris thouarsi (Valenciennes, 1846)

IP

IS

unidenfified echinoid spines

14

74 THE NAUTILUS

April 30. 1980

Vol. 94 (2)

Arthropoda

Cirripedia

Balanus sp, indef.

Te^^aclito squamoso rubescens (Darwin, 1854)

Ostracoda

Bairdio verdesensis LeRoy, 1943

Brodleyg ourifa (Skogsberg, 1928)

Cyprideis (Cypridets) sp. indef,

Cythereis glauca Skogsberg, 1928

Legumir>ocythereis corrugoto Benson, 1959

Loxoconcho lenticulato LeRoy, 1943

Monocerotino sp. indet,

Pgrocypris pocifico LeRoy, 1943

8

o

S

2Pv,2V

IPV, IV

)PV.2V,?

8PV,8VJ

IV

2V

2Pv,2V

IV

IV

Chordato (Fish)

Clevelandia cf. C. ios (Jordan and Gilbert, 1882)

(Otoliths)

Footnotes for Table 1

1. Identified as Eupleuro triquetro (Reeve) by Choce (1956, p. 179).

2. Identified as Ostrea cumingiona Dunker by Chace (1956, p. f78).

3. Identified OS "Pholadsp. (a fragment) " by Oiace (1956, p. 178)= Penlteiio fitchi Turner, 1955, fide Kennedy (1974, p. 45).

4. Identified os Trgchycordium procerum (Sowerby) by Chace (1956, p. 178).

5. Identified by E. C. Allison.

6. Present in C.A.S. loc. 34312 = 0624.

Vol. 94 (2)

April 30, 1980

THE NAUTILUS 75

geology and collecting stations before his tragic

and untimely death while on a geological recon-

naissance in Sonora, Mexico, on January 1, 1971.

I have attempted to complete these remaining

sections largely on the basis of brief notes he had

prepared for an outline of the manuscript, which

were kindly forwarded to me by his wife,

Eleanor. I would like to dedicate this paper,

despite its obligated briefness, to the memory of

Ned Allison, a close friend and a most valued col-

league, for sadly Ned was not able to complete

many of the projected studies which he had pur-

sued with his characteristic vigor and en-

thusiasm.

Previous Work

Jordan and Hertlein (1926) briefly described

the stratigraphy of the region and noted the

presence of fossiliferous Pleistocene sands and

gravels overlying the Tertiary beds of the area.

They also recorded and described Pliocene

megafossils, largely mollusks, from five localities

in the general vicinity of Turtle Bay. Most of

these collections were made by G Dallas Hanna

in 1922, and by Hanna and Eric K. Jordan in

1925. Some of the Pliocene pectinids had been

described in an earlier paper by Hertlein (1925).

Hertlein (1933) later listed additional species of

Pliocene mollusks and echinoids and reported the

presence of Miocene diatomaceous shale, resulting

from his field work at Turtle Bay in 1932.

Beal (1948, p. 80), in a geological recon-

naissance of Baja California, cited Pliocene

fossils, including mollusks, echinoids, and bar-

nacles, from several localities near the bay, as

well as listing the species previously reported by

Jordan and Hertlein (1926). Chace (1956) recorded

Pliocene and Pleistocene invertebrates, mostly

mollusks, obtained by him in 1954, during a brief

visit to Turtle Bay. He was the first to identify

specifically Pleistocene metazoan fossils from this

area and his records are included herein (Table

1). Minch, et al. (1976), in a review of the geology

of the Vizcaino Peninsula, briefly described the

terraces of the region and listed the Pleistocene

fossils reported by Chace (1956) from Turtle Bay.

Ortlieb (1979) summarized the status of his

studies on the Quaternary marine terraces along

the southwestern coast of Vizcaino Peninsula. He

recorded the presence of fossiliferous terrace

deposits of late Pleistocene age at elevations of

approximately 5 and 12 meters in the vicinity of

Turtle Bay. The fossils described herein were col-

lected from some of these terrace deposits.

Topography

Turtle Bay (Figure 2) is nearly circular in

shape with a diameter of about 2.5 miles (4 km.).

Capelike rocky headlands with high bluffs border

the entrance to the bay and they are separated

by approximately a mile (1.6 km.) of mostly open

water. Kelp Point (Punta Sargazo), with an eleva-

tion of 9 meters, forms the northwestern entrance

to the bay and rises steeply towards Mount Bar-

tolome (Monte Bartolome', elevation 27 meters) to

form a prominent headland to the west. Cape

Tortolo (Cabo Tortolo), a narrow promontory, at-

taining 127 meters in elevation, terminates as a

rocky point about 6 meters high to form the

southeastern entrance of the bay. A low reef ex-

tends from this peninsula northwesterly for a

distance of nearly a mile (1.6 km.) to form a

natural breakwater against the open sea.

Southeast from Cape Tortolo, a rocky highland

(Monte Belcher) borders the coast with sea cliffs

of 8 to 15 meters in elevation and terminates two

and one third miles (3.75 km.) southeastward of

Sebastian Vizcaino Bay

B 3046 (6 M) located 5: 9 7 Km

souihwesi o( Turtle Bay

Thurloe Head

FIG. 2. Sketch (not drawn to scale) showing the approximate

location of the lowest emergent terrace remnants in the Tur-

tle Bay area from which the Pleistocetu; fossils were collected

(E. C. Allison ms.).

76 THE NAUTILUS

April 30, 1980

Vol. 94 (2)

the cape to form a bold headland known as

Thurloe Head.

Northwest of the entrance of the bay, the

coastline consists of rocky bluffs below the

highland forming Mount Bartolome, to about

27°42'N. Here the cliffs give way to a sandy

beach backed by a low plateau with an elevation

of 5 to 7 meters that runs inland to the base of

low hills.

Within the bay, the western shore fronting the

highlands consists of high bluffs, whereas the

northern and eastern sides of the bay possess low

shingle and gravelly sand beaches, which gradual-

ly rise to higher broken country. The bay is

shallow with depths at the entrance of 10 to 12

fathoms (18 to 22 m.) and shoals gradually

toward the inner shore, where the three-fathom

curve (5 m.) is about Vi mile (0.16 km.) distant

from the beach on the northeastern side. The bot-

tom is composed largely of sand, but rocky

substrates occur near the entrance of the bay.

Beds of giant kelp (Macrocystis) are found along

the open coast and within the entrance of the bay

especially off Mount Bartolome (U. S. Navy

Hydrographic chart 21081).

Geological Setting

In the region of the Vizcaino Peninsula, at

elevations of a few meters to 250 meters, marine

terraces mantle coastal rocks and are locally

represented by eight or more separate deposi-

tional levels, ranging in age from late Pliocene to

Pleistocene (Minch et at, 1976). Faulted marine

Pliocene (Almeja Formation), marine Miocene

(Tortuga Formation) and late Cretaceous to late

Jurassic rocks (Valle and Eugenia Formations)

(see: Mina, 1957; Minch et ai, 1976) form the

bedrock platform on which the terrace sediments

were deposited (formational nomenclature after

Kilmer, 1977). Regionally, the fossiliferous terrace

sediments vary in thickness from thin veneers to

beds of 7 or more meters and commonly include

medium to coarse grained, olive-gray litharenite,

interbedded with pebble and cobble conglomerate

(Minch et ai, 1976).

In the vicinity of Turtle Bay, the marine

Pleistocene is distributed in a series of

fossiliferous shoreline deposits preserved as rem-

nants on platforms representing the lowest

emergent terrace in the region. The terrace

deposits are mostly horizontally bedded, but some

terraces are deformed by folding or are tilted by

faulting (Mclntyre and Sheldon, 1957; Minch et

(i/..1976.)

Dr. Allison believed (personal communication)

the shoreline deposits from which the fossils were

collected to represent a single high-stand of the

sea. Post-depositional episodes of deformation

were assumed by him to account largely for the

present differences in the elevations of the ter-

race remnants. Reliable correlation of these

deposits, however, is not likely to be achieved by

traditional stratigraphical methods, owing to the

fragmental preservation of the terraces and the

complex tectonic history of the local area.

Terrace Faunules

More than 140 species of metazoan in-

vertebrates, mostly mollusks, and one fish were

collected by Dr. Allison from six localities in the

vicinity of Turtle Bay (Figure 2). Of these, 129

were identified to the species-level. The species

are listed quantitatively for each collecting sta-

tion (UCMP localities B-3027; B-3007; B-3050;

B-3024; B-3025; B-3048) in Table 1. The fossils are

deposited in the Museum of Paleontology, Univer-

sity of California, Berkeley.

Additionally, the fossils reported from Turtle

Bay by Chace (1956), totaling 54 species of meta-

zoan invertebrates, are included in the faunal

tabulation (Table 1, SDNHM locality 0624

[ = UCMP locality B-3024]). Mr. Chace divided the

collection he made at Turtle Bay in 1954 between

the San Diego Natural History Museum and the

California Academy of Sciences (SDNHM locality

0624 = CAS locality 34312; teste Barry Roth,

1977). Chace 's published report (1956) apparently

was based solely on the SDNHM collection.

The combined collections of Allison and Chace

from the terrace sediments total 139 identified

taxa, as follows: 122 mollusks, 7 bryozoans, 6

ostracods, 2echinoids, 1 cirripedian and 1 fish.

The following review of species diversity of the

collected samples and interpretations of the

depositional ecology of the faunules is based

largely on the molluscan constituents of the

fauna. TTie six collecting stations are indicated on

Figure 2 and the fossils are listed in Table 1 by

stations.

Terrace sediments preserved at an elevation of

4.5 to 6 meters along the bluff facing the sandy

beach on the southwest side of the peninsula

Vol. 91 (2)

April 30, 1980

THE NAUTILUS 77

northwest of Turtle Bay yielded 30 identified

molluscan taxa (B-3027). This essentially open

coast assemblage suggests a mixture of shallow

water, sand dwellers (Olivella, Neverita, Macoma.

Tiveku Tellina, etc.) and rock dwellers (PissureUa.

Lottia, Tegula, Thais, Hinnites, etc.), together

with a deeper water element (Dentalium.

Megasurcula. Astraea. Bursa, etc.). To the

southeast on Kelp Point, the headland forming

the northern entrance to Turtle Bay, fossils were

collected from terrace sediments (B-3007) at an

elevation of about 12 meters. The collection, total-

ing 39 species, includes shallow water and off-

shore elements of rocky substrates (Astraea,

Cypraea, Tegula, Fissurella, Hinnites, Norrisia-an

algal associate, etc.) and sandy substrates (Oliva,

Olivella. Cryptomya, Trachycardium, etc.). This

locality was only partially sheltered from the

open sea on the southwestern coast of an ap-

parently insular Mount Bartolome at the time of

deposition. These assemblages (localities B-3027

and B-3007) contain only temperate-water in-

dicators, as would be expected from largely un-

protected coastal sites.

Along, the northeast side of Turtle Bay, a ter-

race is preserved at an elevation of 4.5 to 6

meters (B-3050). Only 12 species, all temperate

water indicators, were collected from these

"back-bay" sediments. These taxa are mostly

shallow water inhabitants of sandy substrates

(Neverita, Amiantis, Chione, Leporimetis,

Macoma, Protothaca. Trachycardium, lucinids,

etc.), with minor elements of boring (Zirfaea) and

of attaching forms (Anomia). At the time of

deposition, this locality received protection from

a probable insular Mount Bartolome to the west

and from the high land to the northeast (see

Figure 2). The absence of warm-water indicators

may reflect the small size of the sample, a

restricted facies, or possible chronological dif-

ferences.

A terrace extends for several hundred meters,

at an elevation of 24 to 27 meters, along the in-

ner bay side to Cape Tortolo, the peninsula form-

ing the southern entrance to Turtle Bay. These

sediments (B-3024 = 0624) are richly fossiliferous

and yielded 84 species of mollusks and 1 echinoid,

including nearly all of the species (Table 2, Pt. 1)

now confined largely to subtropical and tropical

waters. This assemblage is a mixture of sand

dwellers (Neverita, Nassarius, Terebra,

Phiilhnwtus. Caneellaria, Argopecten, Chione,

Felanielhu Leporimetis Protothaca, Trachycar-

dium., lucinids, etc.) and rocky and sandy rubble

dwellers (Acanthina, Cypraea, Fissurella,

HaliotL% Hipponix, Lottia, Columella, Conus,

Crucibulum, Tegula, Thai% Turbo, Vitularia.

Ostrea), and includes some offshore inhabitants.

On the southeastern side of Cape Tortolo, a ter-

race (B-3025) is preserved at an elevation of 6 to

9 meters from which 12 species were collected, in-

cluding several warm-water indicators. These

molluscan taxa largely represent sandy botton in-

habitants (Oliva, Olivella, Leporimetis, Tivela,

Tresus, etc.) and some rock-gravel dwellers

(Kelletia, Lottia, Tegula, etc.). Dr. Allison noted

that this terrace appears to be tilted upward to

the northwest in the direction of the Cape Tortolo

locality (B-3024), and he suggested that these ter-

races may be coeval depositional features. Both of

these localities at the time of deposition were

situated along the protected shoreline of an in-

sular Cape Tortolo and were partially sheltered

from heavy seas by an insular Mount Bartolome

to the northwest and a most likely insular Mount

Belcher to the southeast.

Approximately six miles (9.7 km.) southwest of

Turtle Bay, another terrace (B-3048), at an eleva-

tion of about 6 meters, extends along the

coastline and faces a long sandy beach. From

these terrace sediments, 12 species were collected

(Astraea, Bursa, Fissurella, Crepidula, Tegula,

Thais, Protothaca, Tivela, Dendraster, etc.), sug-

gesting sandy and rocky habitats in shallow

water to offshore depths. All are temperate in-

dicators, as would be expected from an exposed

coastal site.

Inasmuch as nearly all of the warmer water

indicators occur in the tilted, higher terraces

(B-3024 - B-3025), these assemblages may have

been deposited by an earlier high stand of the sea

than those on the other, lower terrace remnants.

The available paleontological evidence can not be

used with confidence to establish the chronology

of these depositional features.

Modern Biota of Turtle Bay

During the winter of 1974, Brusca (1975)

undertook a survey of the marine biota of Turtle

Bay based on 13 collecting stations representing

78 THE NAUTILUS

April :iU, 1980

Vol. 94 (2)

Toble 2, Part 1 , Southern Founal Element of Turtle Bo/

Speciei who*e modem endpointi of ronge He mainly to the south of Turtle Bay with occurrence* in other lote

Pleiltocene foimoj of Colifomia ond Pacific Baja California ond with present geographic ronge* indicated.

Mollusca

Gastropoda

" Acanthino lugubris

"Anochis coronoto (♦

fonno ha n nana)

Bulla punctulotg

Cancel laria cauidiforrni]

Conthorus e I egons

Cerithium moculosum

California

Los Angeles Boiin San Diego Area

•• «

s ^

B J

V o

t— a.

J

s

_ "E

s >

S 8

^1

t-5

C 3

,7,33

3,4,5,7,33

,12,23

.8,9,10

Mc«ico

West Coast of &ajo Colifofnio

I J

6 6

8" "? o

_J _0 .-

I - "°

I 2 -

i

Modem Geographic Ror^e After

Keen, 1971, unleu otKerwiie noted

*= Modern Range includes loiitude

of Turtle Bay

J6

X Todoj Sontos Boy to Mogdoleno Boy, Bojo

42

California

X Scommon Lagoon, Bojo Colifomia to Ecuodor

X Mogdoleno Boy, Bojo Calrfomio to Ecuodor

X Baltenoi Bay, Elojo Colifomio to Penj

X Punfo Abreojoi, Bojo Colifomia to Peru

X Mogdoleno Boy, Bojo Catifomia to Santo Elena,

Ecuodor^S

Columbella major

* Conus fergusoni

Conus perplexus

Conus purpuroscens

Conua reguloris

'Oucibulum scutel latum

Cyproco onnettoe s.s.

Cyproeo arabicula

Diodoro digueti

"Eupleuro muric iformii

HorTT>ospiro maculoso

*Ma<;ron aethJops

Nerito scobrlcosto

Oliyg inc rosso ta

Olivo polposto (*- forma

dovlioe)

,3 .3,7 3,9,10,11

X Santo Morio Boy, Baja California to Peru

25

X Turtle Boy, Bojo California to Peru

45 25

X Punto Pequena, Bojo Colifornio to Peru

X Santo Morro Boy, Bojo Colifomia to Peru^^

Mogdoleno Boy, Boja Colifomia to Ecuador

X Cedros Island, Bojo California to Peru

X Los Froiles, baia Colifomia to Puerto Penosco,

Sonoro^

X Punto San HipoHto, Bojo California to Peru

? Scammon Lagoon, Boja Californ!a^° to Ecuodor

X Cedros Island, Boja California to Peru

27

45 ,

.,27

Santo Mario Boy, Bajo Colifomia to Ecuodoi

I 5 mi . N . of San Qui nti n Boy to Punto Pequena ,

Bojo Colifomio

Punto Pequena, Bojo Colifomio to Ecuodor

Son Ignacio Logoon, Bajo Colifornio to Peru

Mogdoleno Boy, Bojo California to Peru

Phylloootus eryfhroitomus

Strotnbus grocllJof

S trombus gronulotus

*Terebro ormillota

'Thols biterlolis

Trigonostoma gonJostotno

'Turbo fluctuotus

J .1,5,7,33

X 10 mi. NE of Cope Son Lucas, Bojo Colifornio

to Peru

45 29

X Mogdoleno Bay, Elojo Colifornio to Peru

29

X Mogdoleno Boy, Bojo Colifornio to Ecuodor

X off Scammon Lagoon, Boja California to Peru

X Sonto Morio Bay, Bojo California to Chile

X Puerto Ponosco, Sonoro to Panomo

X Cedros lilarnJ, Bojo California to Peru

Vol. 94 (2)

April 30. 1980

THE NAUTILUS 79

s>

s s

*VIt\jloria tolebroso

-------X Ajuncion lilond, Bojo Gilifornia to Peru

^8,9,10 _ ___ .7 7 7 Cedros Island, Bojo Gilifofnia to Peru

-------x Scommon Lagoon, Bojo Coltfomia to Peru

-------- Manuela Lagoon, Bojo Colifomio to Peru

X ?--- ?- ?? near Magdalene Boy, fiaja Gilifomia to Go/omas,

Sorroro

^8,9,I0,n _ ___ _. J, ^ Cedros Island, Boja California to Peru

x^-* X - - x^^ - - X X Mogdoleno Boy, Bojo G)lifomio^^ to Peru"*^

^l,3^n,14, _ _ _ ^49 _ _ _ ^49 Logypg Beach, Gjlifornio^' to Peru

X ' - --X -- - X Scommon Logoon, Bojo California to Penj

---xx-xx Scammon Lagoon, Bojo California to Peru

X _____--? Son Ignocio Logoon, Bojo California to Peru

-------X Cope Colnett, Baja California to Chile

32

-------X Mogdoleno Boy, Bojo California to Peru

------XX Scammon Lagoon, Baja California to Peru

X ' ---??- ?? San Ignocio Lagoon, Boja California to Costa Rico

x' X------X Cedros Island, Bojo CoMfomia to Guaymos,

Sinoloo^S

-28

? off Scammon Logoon , to ? Punta Eugenia,

Baja Catifornio

Cape Son Lucas, Bojo Colifomio to Ecuador^ ;

Guodolupe lslar>d, 6a|o California^

intertidal and subtidal habitats. He reports

(Brusca, in litt.. 1978) the coldest water

temperatures near the mouth of the bay, where

isolated stands of giant kelp (Macrocystis) occur,

together with algal associations characteristic of

cool water. He found temperatures to increase

gradually within the bay, with warm temperate

and tropical organisms (Panamic species) living

in the warmer backwaters. In a summary of his

study, Brusca (1975) concluded that "tropical

species" (39%) outnumbered "temperate species"

(21%) in the samples, although he noted (in litt..

1978) that the temperate organisms dominated

tropical ones in terms of total biomass (see also

Brusca and Wallerstein, 1979, p. 76).

The mollusks, on the other hand, are

predominately wide-ranging eurytopic species,

with the Panamic element represented by a

minor constituency. The presence of severe

coastal upwelling of cold water in the area

80 THE NAUTILUS

April 30, 1980

Vol. 94 (2)

Toblf* 2. Part 2. NortKem Foimal Element of Turtle Boy

Spociei wfxrte modem endpoinlj of ror^ge He moinly ro the north of Turtle Boy with occurrenceJ in other lo'e

Pleiitocene founos of California and Pacific Bojo California and with present geographic rongei irvdicoted.

Mollusco

Gastropoda

• Alio corinato

• Astroeo undoso

•Biftium quodrifilotum

Colifornio

Los Angeles Basin Son Diego Areo

<^ '2 _ 'E 'E -"

s > s > > ^

s s Bo o .^1

£ £ S

.1,3 .XiJ,33, ','1,14

.,3^7,

U 7,33,4S I2,U,23

x3 .3.7

Mexico

West Coost of Bojo Colifornio

Si S ~ '^

O V

cS 6 a i §

B p £ O I 9 ^ -6

cccco^cg*

35

NVxJem Geogrophic Ronge After

McLeon, 1976, unle» otherwise noted

'= Modern Range includes latitude

of Turtle Bay

Boranof Ulond, Alaska to Son Francisco Island

(Gulf of Colifomio)*5

Avilo Beach, Colifornio to Punta Pequena, Bojo

Californio*5

San Pedro, Colifornio to Sonto Morlo Bay, Bojo

California

•Coecum doj_M [ =*■ C.

licotufn Bortsch,

*Coecum crebicinchjm

'ColHsello lintotulo

* Corpus colifomicus

Cypraeo tpodiceo

•partulum occidentole [= •■

FT^efi Bortsch, 1920]

*Fiuurfl1la volcano

* Holiotii fulgens

*Hipponix tumens

*Kallefio kelleHi

•Lottlo gigonteo

'Magosurculo corpenteriono

"Mitro idoe {= ^M .

cotoTlfw 17011,1919)

*f4assarius tegulo

^1,3

1,2 1,3 3,4,7,

X X X 46

12 1,3 7,44

1,2 1

,10

,10,12

9,11,12,14

X

14,23

X XX

5,7,33,46 ,11,14

,1,2 ,3 ,3,7 ,3,6,12,23

3 7 3, 1 1

- X X X '

2 1 3,7,33 ,3,6,9,12,23

1,3 3,5,6,7,33 3,14,23

- X X X

7 9,11

- - X X

,3 ,5,7,33 ^,11,14

1,2 3 7,33,46 12,14

1,3 3,4,5.6,7, 8,11

« « 3l)

2 3 3,6,7,33, 3,10,11,12,

*Olrvello biplicotQ

* PMudomelatoma

pflnicillolx]

* Ptafoputpwfo faitivo

1,2 2,3 3,4.5.6,7, 9,11,12,14

« « « 33,46 » ' ' '

^3 ,5,7,33

.' x''3 ^*if- .11.'^

XX X

X X

X - X

37

7 ?

SE of Forollon IslorxJs, Colifornio to Asuncion

IslorxJ, Bojo Colifornio

Hesketh Island, Alosko to Los Oucei, Bojo

Colifornio (Gulf of Colifornio)*^

Newport, Oregon to Punto Abreojoi, Bojo

,45

Cnlifomia

X Forolton Islands, California to Mogdaleno Bay, Bojo

California

Monterey Bay to Cedros Island, Bojo Colifornio

X Yukon Island, Alaska to Mogdaleno Boy, Bojo

Colifornia^^

X Oesent City, Colifornio to Mogdoleno Bay, Bojo

Califomio

X Point Conception, California to Mogdaleno Boy,

E^jo California

X Oesconf Gly, Colifornio to Mogdolerw Boy,

Bojo Colifornio

X TojigoM, Sonto Borbaro Co., Colifornio ■*, to

Asuncion IslorxJ, Bojo Colifornio

Neoh Bay, Washington to Turtle Boy,Baja California

34 ,

X Bodego Bay, Califomio to San Oiitobol, Bojo

Colifornio

34

Oescent Cty, Colifornia to Punto Son Pablo,

Bojo Colifornio 45

X X Long Beach, Colifornio to San Ignocio Logoon,

Bojo Colifornio^

X Point Conception , Colifornio to Asuncion Islorxj,

Bojo Cotifomio

X Voncouver lslor>d, Canada to Turtle Boy, Ekijo

Colifornio

X X Sonta Borbaro, California to Migdoleno Boy,

Bojo Colifornio

- X SE Po^nt Conception, Califomio to Mogdoleno Boy,

Bojo Colifornio

Vol. 94 (2)

April 30, 1980

THE NAUTILUS 81

s a,,

0| § £l

5l ^Jl

I _8 Bo S^\

'Scrip montereyentit

'Tegulo oureofincto

*Tegulo eiieni (- T.

Hgulato ouct. no*

M*nke,t850)

'Tegulo gollino

'Triphoro pedfoong

'Truncotello colifomico

1

.5,7,33 JM*

S -o

'6 6 1

- s s ^ ~ ^

.' x'.3 .5jJ33, ,n. 12,14

.2 ,1,3 .3,4.5,7, ,10,11,14,23 .

1,3 3,5,7,33 3,23

X ' X ' ' ' X X

2 1 7,33 10

' K X X X

n

SE Forollon Islonds, Catifornio, to Punia Son Pablo,

Boja Colifofnio**'

K X Rincon Point, Santo Barboro Co., Colifornio to

Mogdoleno Bay, Bojo Colifornio

- X SE Point Mugu, Ventura Co., California to Magdaleno

bay. Boja Colifornio

X Sonto Cruz Islond, California to ? Magdolena Boy,

Bajo California's

X Pacific Grove, Colifornio to Mogdoleno Bay, Bajo

Califofnio'5

Polos Verdes Peninsula, Colifornio to Mogdoleno

Boy, Boja Colifornio"

Bi vol via

• Amiontis collosa

•Chaceia ovoidao

'Cofbulo luteolo

*Donax callfomicus

'Epili

ucing colifomico

Glons subquodrotq

•Hinoitw gigonteui

*Mocomo nosuto (^-for^T»a

Milrwrio minimo

•Nuttolio nuttolii (+

formo orcutti)

• PenihsMo fjtchi

•Penitello penito

Soxidomus nuttol li

*S«inele deciio

' Tallino bodeganiis

•Tivela stullorum

• Troc^ycord i um

quodrggenorii

'Troniennello tonlillo

1 pilsbryi

1,3 3,4,5.6, 3,11

x39 ^39,46 ^39

J x3 ,3,5,7, ,8,9,10,

x' X X ' ^3' X ,,^^4

3 .4,5,6, ^9,10,11

X X 1^ X

x'.2 x1.3 ,3.\l- ''■'W'

1,2 1,3 5,6,7 .11,12,14,

X X • X '"23

x2 ,3 ,3,4,5^6, x'2

of^ - -

3 3,4,7

X X

x39

.39 ^39 ^39

,3 ,3,4.5.7, ,3,12,14

X X -jj X

,3 ,3A5A ii.liH

" " ^.33 "* 33

3 3,4,5,7 3,11,14,23

,3 ,3,5,33 ,8.11.14,46

^3,39 ^3,7,39 ^^10. 14,39

XX X

X Sonto Borbora, Colifornio to Cope Son Lucas,

Boja Colifornio

Sonto Cruz, Colifornio to Turtle Bay, Boja

Colifornio

X Monterey, Colifornio to La P02, Boja California

X Goleto, California to Mogdalena Boy, Ekijo

California^

Oesenf Gty, Colifornio to Son Ignoclo Logoon,

Bojo Califomio'O

X Queen Oiorlotte Islands, Conodo to Punto

Rompiente, Bojo Colifornio"'*

X Aleution Islonds, Alaska to Magdolena Bay, Bojo

Colifornia*^

X Kodiok Island, Alosko to Cape Son Lucas, Bojo

Colifornio38

Monterey, California to Notividad Island, Bojo

California 36

X Bodego Boy, Colifornio to Mogdoleno Boy, Bajo

California

Monterey Boy, ColifornLo to Punto Pequeno,

Bojo Colifornio

Gulf of Alosko to Punto Pequeno, Bojo Colifornio

X Humboldt Boy, California to San Geronimo Island,

Bojo California

X Sonto Barboro, Colifornio to Cope Son Lucas,

Bajo California

X Queen Charlotte Islands, Conodo to Cope Son

Lucas, Bojo Colifornio^

X Stinson Beoch, Marin County, California to

Mogdoleno Boy, Bojo Colifornio

Monterey, Colifornio to Cope Son Lucas,

Bojo Colifornio-'^

Sirko Horbor, Alosko to Boio Colifornio (L.27° N)**^

Arctic Alaska to Mogdoleno Boy, Bojo Colifornio 3'

82 THE NAUTILUS

April 30, 1980

Vol. 94 (2)

I . Woodring, ei^ ol^. , 1944

2. MarincovicK, 1976

3. Arnold. 1903

4. Dclong, 1941

5. Willeti, 1937

6. twil. 1946

7. Kanokoff and Emefiofi, 1959

8. Kerr, 1971

9. Kern, et ol^. , 1971

1 0 . Emcrion ond Oioce , 1 959

II . Herllelnond Grant, 1944

12. Webb, 1937

13. Volenllne, 1961

14. Emerjoo ond Addicotr, 1953

15. Volenline, 1957

16. Emenon. 1956b

17. Addicort ond Emerjon, 1959

18. Jordon. 1926

19. Jordon, 1924

20. Hertleln, 1934

21. Jordon, 1936

22. Keen, 1971

23. Volentine, 1960o

Foornorei to Toble 2

24. Berry, 1922

25. Honno, 1963

26. Collection of the American Muieum of Noturol

Hiftory

27. Herttein ond Strong, 1955

28. Grontond Hertlein, 1936

29. Emenon and Old, 1963

30. Hertlein and Strong, 1943

31. Hertlein ond Strong, 1949

32. Olsion, 1961

33. Volentine, 1956

34. McLeon. 1978

35. Volentine ond Meode, 1961

36. Coon, 1977

37. Monger, 1934

38. Filch, 1953

39. Kennedy, 1974

40. Hertlein ond Gront, 1972

41. Honno, 1963, p. 26, recordi two speciinens

identified os Contn grodotui (which irtay be

refereoble to the present speciesl from the

Pleistocene ot Punta Sonto Rosalia, about

60 miles northeoit of Scommon Lagoon.

42. Closely related, if not conspccific loxo (A.

ongelico ond A . tyrionthina ) , occur in the

Gulf of Cblifotnio OS for soutti os Son Corlos

0. ^ <5

isoy, Ouaymos .

43. Replaced southword and within the Gulf of

Galifornio by N. tiorulg (Kiener, 18411, which

some workers consider to be southern populotions

of this species .

44 . This toxon is opporently conspecific with T,

boirdiono C. B. Adoms, 1852, for which two

lots ore known from the noftfsem part of the

Gulf of Colifomio otxl ofse lot from Tabogo

Island, Ponomo, teste J. H. McLeon.

45. teste J. H. McLeon, bcsed on the collection

of the Los Arsgeles County Museum of Noturol

History .

46. Addicolt, 1964

47. Valentine, 1960b

48. Hoderlie, 1979

49. Coon, 1979

50. Fitch, 1962

(seasonally, from April through July, according to

Blackburn, 1969) accounts for the shallow water

occurrences of temf)erate organisms, including

the luxuriant growth of kelp beds in this region

(Dawson, et al, 1960). The diverse thermal regime

of the hydroclimate of this coast is also sup-

portive of subtropical and tropical organisms,

especially in protected habitats such as shallow

bays and lagoons, where the effects of solar radia-

tion and sluggish circulation locally influence

water temperatures (Emerson, 1956, a, b; Brusca

and Wallerstein, 1979). Within the confines of

Turtle Bay, these contrasting faunal elements are

represented by mollusks associated with kelp

beds (Astraea undosa. Norrisia norrisi, Haliotis

spp., and other temperate species) and by sub-

tropical and tropical species {Bursa caelata.

Pterin sterna. Crepidula i^trudata, and others) liv-

ing together with the more numerous ubiquitous

species, some of which range from Alaska to

Peru.

The ranges of the shelled mollusks living on

the continental shelf of the northeastern Pacific

Ocean have been investigated by computer tech-

niques and other numerical methods in an at-

tempt to define zoogeographic provinces on the

basis of the latitudinal distribution of this major

faunal constituent (Stanton and Dodd, 1970; Ad-

dicott, 1966; Valentine, 1961, 1966; Hall, 1964; for

a general summary .see Brusca and Wallerstein.

1979:72-77). Distributional boundaries are defined

as provincial boundaries and apparently reflect

the regional hydroclimatic patterns controlling

temperature regimes and governing other

hydrographic conditions on the shelf.

Turtle Bay (27°14'N.) is geographically situated

near the northern limit of the subtropical Surian

Province, which extends southward along the

western coast of Baja California from Punta

Eugenia (28°15'N.) to Cape San Lucas (22°52'N.).

In the region of the Cape, this province borders

on the extensive, tropical Panamic Province,

Vol. 94 (2)

April 30, 1980

THE NAUTILUS 83

which includes the Gulf of California and ter-

minates in northern Peru. The Surian Province

borders on the north with the warm temperate,

Californian Province, which ends near Point Con-

ception, California (34°50'N.), the southern boun-

dary of the temperate Oregonian Province, which

extends northward to Dixon Entrance, British

Columbia (54°25'N.), where it is replaced by the

cool temperate Aleutian Province.

Late Pleistocene faunal provinces also have

been defined for the molluscan assemblages

preserved in sediments on the lowest emergent

marine terraces of western Baja California to

Washington (Valentine, 1961; Addicott, 1966;

Kennedy, M. S. ). Valentine (1961, p. 393) pro-

posed the Magdalenan Province, extending

southward from Punta Eugenia to Cape San

Lucas on the west coast of Baja California, as a

late Pleistocene province characterized by faunas

chiefly Panamanian in aspect. The northern

boundary of the late Pleistocene Magdalenan Pro-

vince was questionably placed by Addicott (1966)

to coincide with the northern limits of the

modern Surian Province (Punta Eugenia), owing

to the meager documentation of the Pleistocene

terrace fauna of this region of Baja California.

The faunistic data recorded in this report for the

Turtle Bay Pleistocene assemblages, therefore,

provide additional paleodistributional evidence

for more adequately defining this provincial

boundary.

The presence of a prominent Panamic faunal

component in two of the Turtle Bay faunules

(UCMP localities B-3024; B-3025) confirms the

assignment of these assemblages to the

Magdalenan Province. A reliable provincial

assignment of the remaining Turtle Bay

assemblages requires a better understanding of

the late Pleistocene chronology of the terrace se-

quence in the Turtle Bay area.

Faunal Composition and Comparisons

All of the identified fossils from the seven

localities (Table 1) represent living species. The

composition of the mollusk and echinoid collec-

tion is dominated by taxa whose modern end-

points of range lie mainly to the north or to the

south of Turtle Bay. These predominantly

southern and northern faunal components are

enumerated in Table 2, Parts 1 and 2, respective-

ly, together with the known modem geographic

ranges and the reported occurrences in selected

late Pleistocene faunas of southern California

and western Baja California. Of the identified

mollusks (122 species) and echinoids (2 species),

the southern and northern elements are about

equally represented (38 and 39% respectively)

and they constitute slightly more than three

quarters (77%) of the mollusk-«chinoid collected

fauna. The remaining molluscan taxa (23%)

represent a mostly eurythermal element, whose

components now range widely, living to the north

in boreal or cool temperate waters and extending

southward, commonly at increasing depths, into

subtropical or tropical waters. The modern ranges

of 97 percent of the eurythermal and northern

elements include the latitude of Turtle Bay. The

present northern endpoints of range of 53 percent

of the southern element, however, occur to the

south of this latitude, but nearly all of these

species (92%) now live south of Turtle Bay along

Pacific Baja California, or in the region of Cape

San Lucas. Most of the species of the southern

element also occur in the Gulf of California and

many range as far south as northern Peru. The

two species (Cypraea annettae and Phyllonot'iis

erythrostomus) not knovm to occur at the present

time on the west coast of Baja California live in

the Gulf of California and range southward to

Panama or Peru. Only two species in the collec-

tion {Macron aethiops and Dendraster mzcainoen-

sis), both members of the southern element, are

restricted now in distribution to the west coast of

Baja California, including the latitude of Turtle

Bay, but they are known from late Pleistocene

deposits as far north as the Los Angeles Basin

(Table 2, Part 1).

Although all of the faunas cited in Table 2 are

apparently late Pleistocene in age, absolute dates

based on radiometric ages are available for only

a few Pacific Coast terraces (summary in Ku and

Kern, 1974). Faunistic interpretations, therefore,

are limited largely to comparisons with

physiographically similar deposits. Literature

references (Table 2) to the geographic occurrences

of terrace sediments in the Los Angeles and San

Diego areas require elucidation. Woodring, et al.

(1946) restricted the Palos Verdes Sand to the

marine deposits on the lowest emergent terrace

of the Palos Verdes Peninsula where they

recognized 12 other higher terraces (numbered 2

84 THE NAUTILUS

April 30, 1980

Vol. 94 (2)

to 13 in ascending order). Accordingly, the

records of fossils from the older terraces (2 to 13)

of the Palos Verdes Hills are listed separately

from those of the lowest terrace, identified as

"Terrace 1, Palos Verdes Sand." Records for other

deposits in the Los Angeles Basin tentatively

assigned to the Palos Verdes Sand (Kanakoff and

Emerson, 1959) are listed under the heading,

"Palos Verdes Sand, Setuiu Lato." Records for the

San Diego area include fossils presumed to be

from sediments correlative with the Bay Point

Formation (Valentine, 1959; Emerson and Chace,

1959; Kern, 1971; Kern, et at, 1971). Kern (1977)

recently demonstrated the presence of more than

one marine terrace level at elevations previously

thought to represent the abrasion platform cut

during the high stand of the sea responsible for

the Bay Point sediments. On the basis of

available faunistic and physiographic evidence,

however, all of these deposits are apparently

referable to the late Pleistocene, and thus invite

faunistic comparison within this limited temporal

framework. In this context, the following

paleogeographic interpretations of the Turtle Bay

fauna are undertaken.

When the faunal elements of the Turtle Bay

assemblages are compared with the constituents

of most of the well-documented, late Pleistocene

molluscan and echinoid faunas recorded from

western Baja California and southern California,

the southern element (subtropical and tropical

sf)ecies) is found to be well represented in the

Magdalena Bay fauna (with 94 percent of the

taxa definitely and questionably identified) and

the northern element (temperate species) is also

abundantly represented in the Los Angeles Basin

(100%) and in the San Diego area (88%), see

Table 2. In contrast, the southern element in the

Magdalena faunules is less well represented in

the Los Angeles Basin (36%) and in the San

Diego area (26%), whereas the northern element

in the Magdalena faunules is more completely

represented in the longitudinally intermediate

Pleistocene sites listed in Table 2, but most of

these faunas represent open-coast depositional

sites from which constituents of the southern

faunal element would not be expected (Emerson,

1956b; Addicott and Emerson, 1959; Valentine,

19(51; Addicott, 1966).

This is a late Pleistocene regional pattern of

distribution in which the southern element

(subtropical and tropical species) becomes pro-

gressively less prominent in deposits at increas-

ingly higher latitudes. For the northern element

(b(jreal and temperate species) this latitudinal

trend is reversed (but not to the same

magnitude). This distributional pattern is also

reflected in the composition of the regional

modem fauna, but with a diminution in the

ratio of Panamic elements to Californian

elements especially noticeable north of the Viz-

caino Peninsula. The coexistence of numerous

locally extinct southern and northern modem

species in Pleistocene sediments, however, con-

tinues to be an enigma to the student of

biogeography.

The terrace associations in which the ex-

tralimital southem and northem species coexist

are termed "thermally anomalous," because ther-

mal changes in the hydroclimate are presumed to

be largely responsible for the shifting of ranges of

taxa that have become geographically separated.

The paleoclimatic significance of the thermally

anomalous associations have been discussed by

numerous workers, including Woodring, et al.

(1946, p. 86-90), Emereon (1956 a; b, p. 326-327).

Valentine (1955, p. 465-468; 1961, p. 393-400), Ad-

dicott (1966, p. C16-19), Kern (1971, p. 819-820;

1973, p. 26-33) and Zinsmeister (1974, 84-94). The

generally accepted explanation of climatic expan-

sion, in which isothermal shifts permit the local

coexistence of thermally anomalous species by

producing warmer "summer" water temperatures

and at the same time intensifying upwelling of

cooler coastal waters has been questioned by

some workers. Kem et al. (1971, p. 337) succinctly

summarized the major objections to climatic ex-

pansion: "The geographic ranges of these

[northern species] and the extralimital [southem]

species must involve more complex changes than

simple warming or cooling. It must also be

recognized that some of these species may have

changed physiologically and ecologically since

late Pleistocene times and some of these may be

limited geographically by factors other than

water temperature." Zinsmeister (1974, p. 84) of-

fered a modified expansion hypothesis stating

"... that some of these anomalies resulted from

periodic local and temporary current changes

that permitted the introduction of larvae of

Vol. 94 (2)

April 30, 1980

THE NAUTILUS 85

tropical moUusks into areas of cooler water

temperatures." He documented his thesis with

records of incursions of subtropical and tropical

elements into the waters of southern California

during historical times. Such periodic incursions

during warm years are of a brief duration

(generally 2-3 years) and the short-term, surviv-

ing populations are not believed to be reproduc-

tively viable (Hubbs, 1948). This distributional

mechanism alone seemingly would not account

for the diversity of the tropical extralimital

species (Kanakoff and Emerson, 1959, Table 2;

Valentine and Meade, 1961, Table 10) found in

the Pleistocene sediments, and could not account

for the presence of most non -pelagic organisms.

However, as Kern (1973) and others have

pointed out, the possibility of physiological and

ecological adaptive changes in species can not be

discounted, but such alterations of tolerances are

difficult to document. An example of ecologically

adaptive changes interpreted on the basis of shell

morphology is inferred by Campbell and Valen-

tine (1979) as a response to differing terrestrial

temperatures during tidal exposures in

Pleistocene Nucella lamellosa. Changes in

temperature-distribution relationships in

molluscan species in which shell morphology is

not seemingly altered are more difficult to

substantiate (Woodring, 1951). Stanton and Dodd

(1970) and Kern (1973), for example, concluded

that the bivalve genus Dosinia, long recognized as

a warm-water indicator in the west coast Ter-

tiary owing to its presence in the modern Surian

and Panamic faunal provinces, had undergone a

change in thermal requirements since the early

Pliocene, where it occurs in assemblages

dominated by cooler water indicators. Valentine

and Meade (1961, p. 35) found isotopic

temp)eratures yielded by Pleistocene specimens of

D. ponderosa to be somewhat lower than expected

for its modern thermal regime, and suggested

that temperatures at which this species can

deposit shell material were lower than those

". . . necessary at some other time in its life for

some other function." In a study of the Pliocene

San Diego Formation, Hertlein and Grant (1972,

p. 38) described D. ponderosa diegoana as a new

"subspecies" intermediate in shell characters be-

tween the early Pliocene D. jacalitosana and the

living D. ponderosa, on which Kern (1973) based

his interpretations of the thermal requirements

of D. jacalitosana from the Pliocene of the Ven-

tura Basin of California. Dosinia ponderosa is

recorded from warmer late Pleistocene

assemblages in the Los Angeles and San Diego

area and southward (Table 2, Pt. 1), but is not

known from the early Pleistocene assemblages of

the Los Angeles Basin, which are generally inter-

preted as cool water faunas (Woodring, et ai,

1946). For this example, the evidence, though not

complete, suggests that some species-groups

within a genus may have higher thermal re-

quirements for critical functions other than shell

deposition, or the presence of discrete, but not

easily detected morphological differences in shell

charactei-s, may reflect species-level evolution

within temporally isolated populations of a

lineage, rather than physiologically divergent

species.

Occurrences of some extralimital species un-

doubtedly have resulted from factors other than

climatic influences, but such inferences require

rigid documentation. The recent discoveries of

wide-ranging fluctuations of the Pleistocene

marine climates during geologically brief periods

of time, determined by isotopic records preserved

in oceanic cores (see Shackleton and Opdyke,

1973; 1976), provides stronger support for the role

of climatic expansion in explaining the ex-

tralimital species associations.

The available paleontological data suggests that

a northward latitudinal shift of about 3 degrees

of the modern hydroclimate of Baja California,

together with a concurrent increase in seasonably

induced upwelling,^ would appear to be sufficient

to support a gradual, attenuated distribution of

the thermally anomalous southern and northern

species within, respectively, increasing or decreas-

ing latitudinal gradients.^ Unfortunately, the

composition of the modern and Pleistocene

faunas of critical areas of Baja California must

be better known before such a distributional

' The occurrence of regional upwelling during interglacial

phases of the Sangamon is supported by oxygen-isotope com-

position of Mytiliis shells from an open-coast site on the

Nestor Terrace. (Killingley and Berger. 1979).

' Indirect paleontological evidence supports regional episodes

of hydoclimatic latitudinal shifts of this magnitude during

the Pleistocene. For example, a compari.son of the U-series

calibrated isochron with kinetic model isochrons suggests that

86 THE NAUTILUS

April 30, 1980

Vol. 94 (2)

model can be realistically evaluated. Additional-

ly, absolute dates of the regional terrace

sediments are needed to provide a more precise

geochronological context. The only radiometric

dates available for the Magdalenan provincial

faunas are 116,5(X) ± 6,(X)0 years for the

Magdalena Terrace in Magdalena Bay (Omura,

Emerson, and Ku, 1979). These values suggest this

terrace is correlative with the Nester Terrace in

the San Diego area and other regional terraces

which apparently were formed by a high stand of

the sea about 120,(X)0 - r25,00(J years ago (Ku

and Kern, 1974) during a warm water stage of

the Sangamon (isotopic stage 5e of Shackleton

and Opdyke, 1973). The assemblages from Turtle

Bay in which the warm-water indicators occur

(localities B-3024 and B-3025) are probably

referable to this early stage of the Sangamon.

More precise dating of these assemblages and

reliable correlation of the assemblages which ap-

parently lack warm-water elements (localities

B-3027, B-3007, B-3050, and B-3048) must await

absolute dating of the fossils.

Register of Localities

Pleistocene, Tuiile Bay area.

Baja California Sur, Mexico

California Academy of Sciences

C. A. S. loc. 34312. Between south end of Turtle

Bay and the ocean. Fossil exposure about .4

kilometers from the shore line and the upper part

of exposure about 15 meters above the high tide

line. Shells mostly picked from a soft clay matrix,

some picked up lower down in the slope. Col-

lected by E. P. Chace, July 16, 1954. [S. D. S. N.

H. loc. 0624 and U. C. M. P. loc. B-3024].

San Diego Natural History Museum

S. D. N. H. M. loc. 0624 . Southwest corner of

Turtle Bay, at south end of hills on the peninsula

between the bay and the Pacific Ocean. Top of ex-

posure at an elevation of about 15 meters. Col-

greater air and/or ground paleotemperature reductions have

occurred in coastal southern California (-4°C. for the Nestor

Terrace) than in southern B;tja California (-!' to -2°C. for the

Magdalena Terrace) during glacial phase.s of the past 120.(XK)

years (Wehmillerand Emerson, 1980).

lected by E. P. Chace. July 16, 1954. [= U. C. M.

P. loc. B-3024 and C. A. S. loc. 34312].

University of California Museum of

Paleontology: E. C. Allison, collector

U. C. M. P. loc. B-3027. Terrace immediately

behind long sandy beach along southwest portion

of peninsula northwest of Turtle Bay. Elevation

4.5 to 6 meters. June 27, 1956.

U. C. M. P. loc. B-3007. Terrace deposit at

aljout 12 meters elevation N. 30°E. of peak on

south side of entrance to Turtle Bay. Jume 18,

19.56.

U. C. M. P. loc. B-3050. Terrace along the north-

east side of Turtle Bay. Elevation 4.5 to 6

meters. July 3, 1956.

U. C. M. P. loc. B-3024. Terrace, traceable for

several hundred yards, at an elevation of 24 to 27

meters, southwest portion of Turtle Bay in back

and south of small fishing camp. June 26, 1956.

U. C. M. P. loc. B-3025. Terrace at an elevation

of 6 to 9 meters southwest of B-3024, and possibly

equivalent to B-3024, as the terrace appears to be

tilted in that direction. June 26, 1956.

U. C. M. P. loc. B-3048. Terrace at an elevation

of approximately 6 meters that extends along the

open coast adjacent to a long sand-gravel beach,

about 9.7 kilometers southeast of Turtle Bay. Ju-

ly 2, 1956.

ACKNOWLEDGMENTS

Dr. Allison was provided trasportation by ship

to Turtle Bay through the ciniperation of the

University of California, Scripps Institution of

Oceanography, La Jolla. California. Facilities in

the field were made available to him by Donald

B. Mclntyre and John S. Shelton of Pomona Col-

lege, Claremont. California, who were conducting

a field class as part of a continuing investigation

of the gefjlogy of the Vizcaino Peninsula and the

adjacent offshore islands.

J. Wyatt Durham and Joseph H. Peck, Jr., of

the Museum of Paleontology, University of

California, Berkeley (U. C. M. P. ), Peter U.

Rodda and Barry Roth of the California

Academy of Sciences (C. A. S.), and Arnold Ross

and Emery P. Chace of the San Diego Natural

History Museum (S. D. N. H. M.) kindly lent me

fossils and/or permitted access to collections in

their respective institutions.

Vol. 94 (2)

April 30. 1980

THE NAUTILUS 87

The following colleagues generously indentified

fossils representing their respective specialties:

John E. Fitch, California Department of Fish and

Game Marine Resources Agency, fish otoliths;

Leo G. Hertlein and Allyn G. Smith, California

Academy of Sciences, echinoids and chitons; John

D. Soule, Allan Hancock Foundation; University

of Southern California, bryozoans; and George L.

Kennedy, pholadid bivalves. Richard C. Brusca,

Allan Hancock Foundation; James H. McLean

Patrick I. LaFollette, and Helen DuShane, Los

Angeles County Museum of Natural History; and

Frank R. Bernard, Fisheries and Marine Service

of Canada, also contributed data of various kinds.

William E. Old, Jr. of the American Museum of

Natural History provided technical service and

Cristina L. Ordonez typed the final draft of the

manuscript.

George L. Kennedy, Frank H. Kilmer and Leslie

F. Marcus critically read a draft of the manuscript,

for which we thank them.

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FRESHWATER BIVALVES OF TYGART CREEK, NORTHEASTERN KENTUCKY

Ralph W. Taylor

Dept. of Biological Sciences

Marshall University

Huntington. W.VA 2.5701

ABSTRACT

A survey of the freshwater bivalves of a small northeastern Kentucky stream

revealed twenty one species of unionacean and three species of sphaeriacean clams,

all reported for the first time from this area.

Several investigators have studied Kentucky

bivalve mollusks. Isom reported on the clams of

the Tennessee River (1969) and the Green River

(1974), both of which are located in vi'estern Ken-

tucky. Stansbery also collected in the Green River

(1965) and did additional work on the Cumber-

land River (1969) which is located in southcentral

Kentucky. Blankenship and Crocker (1972) sur-

veyed the Rockcastle River in southeastern Ken-

tucky and Branson and Batch (1971) collected

throughout much of the state with most of their

efforts concentrated in eastern Kentucky. Much

of this work was concerned with land and aquatic

snails, and the only bivalves reported were

sphaeriacean clams. Williams (1969) comprehen-

sive survey of the lower Ohio River basin con-

tributed significantly to the knowledge of the

molluscan fauna of Kentucky's largest major

waterway.

Little work has been done in smaller streams

of this area and I find no mention in the liter-

ature of any work carried out in the northeastern

sector of Kentucky. The intent of this paper is to

report on the occurrence and specific location of

21 species of unionacean clams and 3 species of

sphaeriacean clams in a small Ohio River Tribu-

tary near the Kentucky-Ohio-West Virginia state

lines.

Collecting area

The Tygart Creek basin is located in Carter and

Greenup Counties in northeastern Kentucky. The

direction of flow is southwest to northeast begin-

ning in Carter County and terminating at its

confluence with the Ohio River near South

Shores. Greenup County. Kentucky. The stream

falls 187 m in its 143 km length for an average

fall of 1.3 m per km (USAGE. 1977). The head-

9(1 THE NAUTILUS

April 30, 1980

Vol. 94 (2)

TABLE I. A checklist of Mussels of Tytimi

Creek. Numbers in parentheses represent total

n u m her ofspecim e )ui collected.

Species collected

Unionacean Clams

Copbicula manilensis (6 )

Quadnila £. pustulosa (2)

Amblema £. pi icata (25)

Epioblasma tnquetra (13)

Tritogonia verrucosa (10)

Potamilus alatus (2 )

EUiptio dilatatus (11)

Obovaria subrotunda ( 5)

Lampsilis radiata luteola (69)

Strophitus u. undulatus (17)

Leptodea fragilis ( 5 )

Lampsilis ventncosa (19)

Cyprogenia irrorata ( 1 )

Lasmigona costata (7)

Ptychobranchus fasciolare (44)

An^donta g. grandis (2)

Villosa iris (2)

Fusconia (22)

Lasmigona compressa ( 1 )

Sphaeriacean Clams

Sphaerium simile (1 )

Sphaeriom striatinum (6 )

Musculium transversum (IS)

Station No.

12 3 4

water area of Tygart Creek is characterized by

narrow valleys with steep wooded hillsides. Only

near the mouth is there a flood-plain of any ap-

preciable size. The stream proper consists of a

series of riffles and pools with a maximum depth

along its course of just under 2 m at summer

pool.

T>'gart Creek is one of rather high water quali-

ty with pollution of the area being limited to

that which results from local agricultural prac-

tices and to a minimal degree from input by

residential human waste. There are no city sewer

or industrial waste disposal systems that empty

directly into the creek.

METHODS

During the period of 27 June-21 October 1977

mu.ssels were collected in Tygart Creek. The

bivalves were hand picked from the water and

along the bank as dead shells. In one instance a

raccoon midden provided a good cross section col-

lection of the mussel fauna in that area. In this

report no distinction is made between specimens

collected as live animals or dead shells. All dead

shells showed little erosion and appeared to have

been recently vacated. Many sites were visited

during the collecting phase but only five localities

were productive. Scientific names are in accord-

ance with Dr. David H. Stansbery of the Ohio

State Univei-sity Museum of Zoology where

voucher specimens have been placed.

Collecting stations

Station (1) Located along St. Rt. 7, 200 m

north of a covered bridge which connects Co.

Rd. 1215 with St. Rt. 7., Greenup Co. A 100

m long shallow riffle with a rather swift cur-

rent flowing over large rocky rubble

characterize this site. The stream width is

approx. 20 m.

v/Ki

Study Ar<

Vol. 94 (2)

April 30, 1980

THE NAUTILUS 91

Station (2) Located alonj,' Co. Rd. 121.S, 1.12

km S. E. of a covered bridge which connects

Co. Rd. 1215 with St. Rt. 7, Greenup Co. A

50 m long slow moving pool followed by a

short swiftly flowing riffle and associated

gravel bar characterize this site. The bottom

of the pool is covered by a 15 cm layer of

mud with a dense algal mat. The stream

width is approx. 10 ni.

Station (-3) Tygart Creek northwest of the in-

tersection of St. Rt. 7 and Co. Rd. 2070

(locally knovm as White Oak Road), Greenup

Co. A long shallow riffle with a shaley rub-

ble substrate is characteristic of this site.

The stream width is approx. 10 m.

Station (4) A small unnamed tributary of

Tygart Creek that originates in Cascade

Cave. The collection site is located 300 m

northeast of the Cascade Caves Park In-

formation Center off Co. Rd. 209. (Carter

Co.) This site is located in a swiftly flowing

steep gradient brook with alternating riffles

and pools. The substrate varies from sand

bars to large boulders. The greatest stream

width is 5 m.

Station (5) Tygart Creek under 1-64 overpass,

0.8 km west of U. S. 60 and 1-64 interchange.

(Carter Co.) The stream here is relatively

small and composed mostly of shallow riffles

with an occasional deeper pool usually of

less than 1 m depth. The substrate in-

corporates alternately sand bars and fine

pebbles.

DISCUSSION

A total of 21 species of clams were found to be

resident to this small stream. This relatively

large number of species for such a small stream

indicates that the water quality and habitat are

conducive to habitation by a wide diversity of

bivalves. All species reported herein have been

previously reported ft-om Kentucky in one or

more of the papers in the introduction. None of

the clams appears on Stansbery's list of rare and

endangered species (1971).

From the wide diversity of types and sizes of

the specimens collected it seems that the popula-

tion is healthy, stable and replenishing itself

while suffering little if any as a result of the pro-

gress of man.

ACKNOWLEDGMENTS

I wish to thank the following for their help in

the collecting of specimens: Dwight ('hal'fee, Jim

Ditty, Kerry Bledsoe, Steve Lawton, Marion Mal-