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VOL. 3 1965-1966

MALACOLOGIA

International Journal of Malacology

Revista Internacional de Malacologia Journal International de Malacologie Международный Журнал Малакологии

Internationale Malakologische Zeitschrift

MUS. COMP. ZOOL. LIBRARY

JUN 21 1966

HAR Va UNIVERSITY

DATES OF PUBLICATION

At least 50 copies of MALACOLOGIA were mailed to subscribers (including a free copy to the Library of Congress, Washington, D. C.) on the following dates:

Vol. II, No. 1 August 31, 1965

Vol. Ш, No. 2 December 9, 1965 Vol. HE No.3 May 31, 1966

iv

MALACOLOGIA, VOL. 3 CONTENTS

. J. BOSS

Symbiotie eryeinaeean Divalves.. . .... еее...

. R. CLARKE

“Growth rings” in the beaks of the squid Moroteuthis ingens (Oeconsidacs Onychoteuthidae) =. iy. ar... 4 4h Joue, eb e

. C. DAZO

The morphology and natural history of Pleurocera acuta and Goniobasis livescens (Gastropoda: Cerithiacea: Pleuroceridae)

. H. FRANK and A. Н. MEYLING

A contribution to the conchometry of Biomphalaria pfeifferi IBasemmatophbora:, Planorbidae) o. be ke ee Zac...

. T. GHISELIN Reproductive function and the phylogeny

Портосе PaAStrOpods 060 «eae a nt dora cette el,

. O. GREGG and D. W. TAYLOR

Fontelicella (Prosobranchia: Hydrobiidae), a new genus of west

AMERICAN. TreEShwateriSnarlis: не Soc ene bse Reese nies

. N. GRUSOV

The endoparasitic mollusk Asterophila japonica Randall and Heath (Prosobranchia: Melanellidae) and its relation to the parasitic gastropods ..............

. LAURSEN

Dhereenus-Myain'the-Aretie region... 2... 20 0 0 LU a aw hee

. L. McALESTER

Evolutionary and systematic implications of a transitional

Ordeyieianzlucinoidäpivalvery. Le as ee eee ee

. McCLARY

Statocyst function in Pomacea paludosa (Mesogastropodas-Ampullariidae) 71.12. IH 2 ee:

. MARCUS

Some Opisthobranchia from Micronesia... 2.6. еее.

. MARCUS and J. B. BURCH

Marine euthyneuran Gastropoda from Eniwetok Atoll,

WEST aci cle dence т.

MALACOLOGIA, VOL. 3

К. N. NESIS

Ecology of Cyrtodaria siliqua and history of the genus

Cyrtodaria (Bivalvia: Hiatellidaeht ........ 2... ao ae ee 197 C. M. PATTERSON and J. B. BURCH

The chromosome cycle in the land snail Catinella vermeta

(Stylommatophora: (Succineidae) aici te una cha Naar Fame oie 309 H. VAN DER SCHALIE and G. M. DAVIS

Growth and stunting in Oncomelania (Gastropoda: Hydrobiidae)..... 81

S. K. WU

Comparative functional studies of the digestive system of the muricid gastropods Drupa ricina and Morula granulata........ 211

vi

Tom 3 МАЛАКОЛЕНИЕ Май 1966

ОГЛАВЛЕНИЕ Страница,

К. КЕННЕТ

Симбиотические двустоврчатые надсемейства,

Еяус ac ea . . . . . . . . . . . . . . . . . . . . . o . . 183 MATES КЛАРЕЗ

"Кольца роста" на клюве кальмара Moroteuthis ingens

(Oegopsida: Onychoteuthidae). «5 = «5 ее + + + + + te о we COT Б. К. ДАЗО

Морфология и история жизни Pleurocera acuta и Goniobasis

livescens (Gastropoda: Cerithiacea: Pleuroceridae). ........ 1 Г. X. ФРАНК И A. X. МЕЙЛИНТ

Конхометрия пресноводной улитки Biomphalaria pfeifferi

(Basemmalophprar Planorbidae) 2 y lie a nm... a 5819 ШТ. гИЗЛИЕ

Репродуктивные Функции и Филогения заднежаберных

ВЕН О оков «ee Gu. a Da at an QUE ae аъ ae В. 0. ГРЭГГ ИД. В. ТЭЙЛОР

Fontelicella (Prosobranchia: Hydrobiidae),

новый pol. западно-американских пресноводных улиток. . . „103 ВЕ. ГРУЗОВ

Зндопаразитический моллюск Asterophila japonica

Randall et Heath (Prosobranchia: Melanellidae)

и его связь с паразитическими брюхоногими +. +. + +. + + + .111 Д. ЛАРСОН

Примета А i Mlle, По Le ее сб в 9999 А. Ли. МкАЛИСТЕР

Эволюционные и систематические проблемы

промежуточных люциноидных двустворчатых +. 2 + + + + + + 2433 А. МаккЛЕЙРИ

Функционирование статоцистов у пресноводной

улитки Ротасеа paludosa (Mesogastropoda: Ampullariidae) . . . . .419 Э. МАРКУС

Некоторые заднежаберные моллюски из мкронезии +. +. + + + .263

Ш

Э иМАРКУ СТИ. Б.'БЕБУ

Морские брюхоногие моллюски подкласса Euthyneura

из атолла зниветок западной части великого океана . +. . .235

vii

МАЛАКОЛЕНИЕ

К. H. НЗЗИС Экология Cyrtodaria siliqua и история жизни рода Cyriodaria (BivalvianHiatelidae). 2. 1. le masa нее м

С. Mo ПАТТЕРСОНИИ Me. Bs БЕРЧ Хромосомные циклы у наземиой улитки Catinella vermeta (Stylommatophora: Succeineidae). „ее 2.0 © 0. in Oe

Г. ВАН ДЕР ШАЛЭ И Г. М. ДЭЙВИС Рост и его замедление у Oncomelania (Gastropoda Нуакорнаае) зо о с о RC

Mo о ВА

Сравнительное исследование пищеварительного процесса у брюхоногих Drupa vicina и Morula granulata . . . . „211

viii

MALACOLOGIA, VOL. 3

NEW NAMES

GASTROPODA

Fontelicella, Gregg & Taylor, 1965, 103 californiensis, (Fontelicella), Gregg & Taylor, 1965, 109 Natricola, Gregg & Taylor, 1965, 108 Microamnicola, Gregg & Taylor, 1965, 109 musetta, (Haminoea), Marcus Burch, 1965, 239 linda, (Haminoea), Marcus Burch, 1965, 241 briqua, (Chromodoris), Marcus Burch, 1965, 245 mietta, (Herviella), Marcus Burch, 1965, 252 evelinae, (Onchidella), Marcus Burch, 1965, 253 illus, (Stiliger, Ercolania), Marcus, 1965, 267 bayeri, (Elysia), Marcus, 1965, 270

тата, (Elysia), Marcus, 1965, 270

cuis, (Hypselodoris), Marcus, 1965, 272

lora, (Discodoris), Marcus, 1965, 273

ylva, (Discodoris), Marcus, 1965, 275

lonca, (Catriona), Marcus, 1965, 279

urquisa, (Catriona), Marcus, 1965, 279

rehderi, (Noumeaella), Marcus, 1965, 282 evelinae, (Muessa), Marcus, 1965, 283

Muessa, Marcus, 1965, 282

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VOL. 3 NO. 1 AUGUST 1965

MALACOLOGIA

1

>

a

MUS. COMP ZOO!

LIBRARY

SEP 16 1905

HARVARD

ternational Journal of Malacology Revista Internacional de Malacologia Journal International de Malacologie Международный Журнал Малакологии

Internationale Malakologische Zeitschrift

MALACOLOGIA

ANNE GISMANN, General Editor 19, Road 12 + Maadi, Egypt UA. Re

J. B. BURCH, Managing Editor Museum of Zoology The University of Michigan Ann Arbor, Mich. 48104, U.S.A.

EDITORIAL BOARD

SCHRIFTLEITUNGSRAT

P. O. AGÓCSY Magyar Nemzeti Múzeum Baross U. 13 Budapest, VIII., Hungary

C. R. BOETTGER Technische Hochschule Pockelsstrasse 10a Braunschweig, Germany

A. H. CLARKE, JR. National Museum of Canada Ottawa, Ontario Canada

C. J. DUNCAN Department of Zoology University of Durham South Rd., Durham, England

E. FISCHER-PIETTE Mus. Nat. d’Hist. Natur. 55, rue de Buffon Paris V®, France

A. FRANC Faculté des Sciences 55, rue de Buffon Paris V©, France

P. GALTSOFF P. O. Box 167 Woods Hole, Mass. U.S.A.

T. HABE National Science Museum Ueno Park, Daito-ku Tokyo, Japan

A. D. HARRISON University College of Rhodesia & Nyasaland Salisbury, Rhodesia

K. HATAI Inst. Geology & Paleontology Tohoku University Sendai, Japan

РЕДАКЦИОННАЯ КОЛЛЕГИЯ

N. А. HOLME Marine Biological Assoc. U.K. The Laboratory, Citadel Hill Plymouth, Devon, England

G. P. KANAKOFF Los Angeles,County Museum 900 Exposition Boulevard Los Angeles, Calif., 90007, U.S.A..

A. M. KEEN Department of Geology Stanford University Stanford, Calif., 94305, U.S.A.

Y. KONDO Bernice P. Bishop Museum Honolulu, Hawaii, 96819, U.S. A.

H. LEMCHE Universitetets Zool. Museum Universitetsparken 15 Copenhagen ®, Denmark

A. LEMMA

Faculty of Medicine

Haile Sellassie 1 University ° Addis Ababa, Ethiopia

N. MACAROVICI Laboratoire de Géologie Université “Al. I. Cuza” Iasi, Romania

D. F. McMICHAEL The Australian Museum College Street Sidney, Australia

J. E. MORTON Department of Zoology The University of Auckland Auckland, New Zealand

У. К. OCKELMANN Marine Biological Laboratory Grönnehave, Helsingór Denmark

J. M. HUBER, Associate Editor Museum of Zoology The University of Michigan Ann Arbor, Mich. 48104, U.S.A.

CONSEJO EDITORIAL

CONSEIL DE REDACTION

W. L. PARAENSE Centro Nacional de Pesquisas Malacológicas, C. P. 2113 Belo Horizonte, Brazil

J. J. PARODIZ Carnegie Museum Pittsburg, Penn., 15213, К.А,

В. О. РОВСНОМ Chelsea College of Science and Technology London, S. W. 3, England

S. G. SEGERSTRÄLE Zool. Mus. Helsinki University P. -Rautatiekatu 13 Helsinki, Finland

F. STARMÜHLNER Zool. Inst. der Universität Wien Wien 1, Luegerring 1 Austria

J. STUARDO Instituto Central de Biologia Universidad de Concepcion Cas. 301, Concepcion, Chile

W.S.S. VAN BENTHEM JUTTING Noordweg 10 : Domburg The Netherlands

J. A. VAN EEDEN Inst. for Zoological Research Potchefstroom Univ. for C.H.E. Potchefstroom, South Africa

C. M. YONGE Department of Zoology The University Glasgow, Scotland

A. ZILCH Senckenberg-Anlage 25 6 Frankfurt am Main 1 Germany

LS к nn

MALACOLOGIA was established with the aid of a grant (NSF-G24250) from the National Science Foundation, Washington, D. C,, U.S. A.

MALACOLOGIA wurde unter Beihilfe einer Unterstützung (NSF-G24250) der National Science Foundation, Washington, D. C., U. S. A., gegründet.

MALACOLOGIA fut établi avec l’aide d'une subvention (NSF-G24250) de la National Science Foundation, Washington, D. C., U.S. A.

MALACOLOGIA fue establecida con la ayuda de una subvencion (NSF-G24250) de la National Science Foundation, Washington, О. C., Ц. 5. A.

Журнал МАЛАКОЛОГИЯ был подготовлен к изданию при дарственного научного общества в Вашингтоне, США.

помощи субсидии (NSF - 624250) or Tocy-

MALACOLOGIA, 3(1):1-80, 1965

THE MORPHOLOGY AND NATURAL HISTORY OF

PLEUROCERA ACUTA AND GONJOBASIS LIVESCENS WUS COMP. 7001 (GASTROPODA: CERITHIACEA: PLEUROCERIDAE)!,2 LIBRARY Bonifacio Capili Dazo3 SFP 16 1909 ABSTRACT HARVARD DNIVERSI]

Relatively little is known about the Pleuroceridae, a family of freshwater operculate snails common in North America, which comprises, or is related to, medically important melaniid snails in the Far East. Their taxonomy, largely based on shell characteristics, is generally in need of revision. A com- parative study was made of the morphology and biology of 2 species classified in 2 different genera: Pleurocera acuta Rafinesque and Goniobasis livescens (Menke), originating from 4 stations near Ann Arbor, Michigan, and from additional localities in Michigan and Ohio, U. S. A.

The shells and opercula of these 2 species differ: however, the similarities not only of their internal anatomy but also in the general pattern of their life history are so striking, that their position in 2 separate genera is open to question.

Differences in the shell, though quite marked, are not always present, and were hardly discernible in some intermediate specimens. P. acuta is about twice as large. Although the general form and pigmentation of the body are quite similar, P. acuta has a more elongated snout and head-trunk region, and longer and more tapering tentacles. It has a smaller and more elongate foot which may be an adaptation to its bottom dwelling and burrowing habit, while G.livescens has a rounder and larger foot in relation to the head region, which may be associated with its crawling habit. The mantle and sense organs, the general organization of the nervous system, the morphology of the respiratory, excretory, digestive, circulatory and the muscular systems of both species are quite similar; they differ only in size. In the Pleurocerinae the males have no penis. Females have a deep reproductive pit in the neck between the right tentacle and the base of the foot, and a shallow reproductive groove leading to this pit. Otherwise the general pattern in the reproductive system conforms with that of other prosobranchs. The sexes are separate. In both species the reproductive organs of each sex were almost identical and occu- pied the same position. Spermatozoa were of 2 types: the typical (eupyrene) and the atypical (apyrene) form. The former are transferred to the female in spermatophores.

Ecologically, the North American pleurocerids require clean water. Except for Goniobasis they all prefer relatively large habitats. They usually live in sandy or muddy areas in the sheltered portions of streams. Goniobasis lives- cens is found in almost any clean and permanent type of fresh-water environ- ment (springs, swift flowing streams, inland lakes); this species is usually

LA dapted from a dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the University of Michigan.

2This investigation was supported (in part) by a research grant, 5 T1 Al 41-05 (2E-41), from the National Institute of Allergy and Infectious Diseases, U. S. Public Health Service.

3Present Address: World Health Organization, Regional Office for the Eastern Mediterranean, Alexandria, Egypt, U. A. R.

(1)

B. C. DAZO

found crawling on rocks and stones.

Both the laboratory and field observations indicated that mating takes place during the fall. When the temperature falls below 5°C the animals hibernate. They resume activity and begin to lay eggs in spring. The sand-covered eggs of P. acuta are laid in batches of varying sizes and shapes; the number of eggs per mass varies from 1-19. G. livescens lays eggs singly, sometimes 2-3in a row and several centimeters apart; these are usually covered with a thin layer of soil. P. acuta has a greater egg output than С. livescens (15 eggs snail/day as against 4) but has a shorter period of egg-laying (April to June against April to mid-August). In both species embryonic development lasts about 2 weeks.

Growth was most pronounced during the first year (from 0.3 to 10 mm in P. acuta;, 0.3 to 3.8 mm in С. iivescens). When the laboratory-bred snails attained sexual maturity, at 2 years, they were 16.7 and 7 mm long, respec- tively, after which time no appreciable growth occurred. Environmental snails were larger. The normal life span is 3 years but may perhaps extend to 4 years. In P. acuta the sex ratio was about 2:1 in favor of the females; in G. livescens about 5:1. As other prosobranchs, both species feed on red and green algae, desmids, and diatoms. Larval trematodes belonging mainly to the families Azygiidae, Allocreadiidae and Aspidogastridae often heavily para- sitized the liver, gonad, alimentary tract and other organs.

CONTENTS Page Page Reproductive System . . 2.200 35 Male Reproductive System ... . 36 INFRODUC TION es sso ule ae are 3 Female Reproductive System . . 38 SYSTEMATIC POSITION AND Muscular System... ооо 40 HISTORICAL REVIEW :2%:..#.1. 40 3 ECOLOGICAL STUDIES... + 782 41 DISTRIBUTION ............... 9 Description of Habitats... se. 41 Geologic Distribution. ......... 9 те i Geographic Distribution........ 10 Some athe leo eee METHODS AND TECHNIQUES.... 11 Michigan .. ...-. VER 43 Sampling Methods ......... Ses Collecting site in Ohio ....... 44 Limnological Methods ......... 12 Vegetation .. „u. 2... o 46 Maintenance in the Laboratory ... 13 Limnological data. ..... . 0e 46 Preparation of Materials for Influence of Environmental Anatomical Studies ......... 14 Factors.on Shell... ha ee 51 Histological Methods. ......... 16 LIFE HISTORY............... 55 MORPHOLOGICAL STUDIES ...... 16 Mating Habits? i 2). . EEE 55 Shell and’ @perculund . "2... 22... 16 The Egg and Egg-laying PEUR REPIONE AN и. 19 Activities 2.5.0... ete eee 56 senserOrgans it ee, 21 Time of Development in the Egg NEFVOUS SYSTEME 0 elote en. cu 21 and gross Embryology....... 60 Digestive System? 1. codi do 26 Growth. ae CO 60 Alimentary iract 3/24 LL 28 Sexual Maturity and Longevity ... 61 Gtherorsansie.s tin ere 30 Sex: Ratio Hi CA Ce 63 Vascular Systems. 02905420 4 32 Diurnal and Seasonal Excretory System. 4.2: . „u... 34 Activities. oo Sica eee 63 Respiratory System"... ......,. 35 Food and Feeding Habits....... 64

PLEUROCERA AND GONIOBASIS

Contents (cont.)

Page Parasites and Predators ....... 66 DISCUSSION OF PLEUROCERID RS ES e as er, 71 ACKNOWLEDGEMENTS ......... 13 Pires CURE, CITED ео. 74 INTRODUCTION

The melaniid snails of the family Pleuroceridae are common and wide- spread on the North American conti- nent and are the dominant group of fresh-water gastropods in the south- eastern United States. Nevertheless, little attention has been given to the biology of this common prosobranch family. Most of the existing literature pertains to shell descriptions and shell variation and only a few papers deal with aspects of their morphology and natural history.

There are several factors which con- tribute to the neglect this family has suffered: (1) Their greatest abundance and the great majority of species occur in the southeastern United States, which has only recently developed research facilities; (2) the great individual and intrapopulation variation in the various Species and the large number of names superficially applied to this variation has resulted in a taxonomic and nomen- clatural confusion which is discouraging to workers interested in working with the group; and (3) there has been a general failure to culture pleurocerid snails successfully in the laboratory.

The purpose of this investigation was to study aspects of the biology of Pleurocera acuta Rafinesque and Gonio- basis livescens (Menke). These 2 species were selected because: (1) they are common and readily available in the Surroundings of Ann Arbor, Michigan; (2) little is known of their biology; (3) they are important in that they serve

as intermediate hosts for trematode parasites of fresh-water fish and are of interest to parasitologists in that they harbor various other larval flukes; and (4) they are related to medically important melaniids in the Orient4 Also it is hoped that the present work may serve to lay a foundation for further morphology and life history studies on other members of the family and help formulate a new evaluation and a more meaningful revision of the systematics of the Pleuroceridae.

SYSTEMATIC POSITION AND HISTORICAL REVIEW

The Pleuroceridae belong to the sub- class Prosobranchia which are usually bisexual, operculate snails having the gills in front of the heart and crossed visceral nerve commissures producing an 8-shaped loop. This family belongs to the order Mesogastropoda Thiele, which almost corresponds to the Pectinibranchia of earlier authors or to the Ctenobranchia excluding the Steno- glossa, i.e. to the Taenioglossa. The “taenioglossid” radula has 7 teeth, 3 on each side of the median tooth.

The systematic position of Pleurocera acuta and Goniobasis livescens, slightly

modified from Thiele (1929), is as

follows:

Phylum Mollusca

Class Gastropoda Cuvier, 1797

Subclass Prosobranchia Milne-Ed- wards, 1848 (Streptoneura Spengel, 1881)

Order Mesogastropoda Thiele, 1925

Superfamily Cerithiacea Fleming, 1882

4Semisulcospira libertina end Thiara (Tarebia) granifera, which act as the first intermediate hosts of Paragonimus wester- mani, the human lung fluke, and Melanoides tuberculatus, which carries Clonorchis sinensis, the oriental human liver fluke.

B. C. DAZO

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The distribution of Pleurocera acuta in North America.

PLEUROCERA AND GONIOBASIS

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FIG. 2. The distribution of Goniobasis livescens in North America.

6 B. C. DAZO

FIG. 3. The distribution of Goniobasis livescens in Michigan (From Goodrich, 1945).

PLEUROCERA AND GONIOBASIS 1!

FIG. 4. The distribution of Pleurocera acuta in Michigan.

8 B. C. DAZO

Family Pleuroceridae® Fischer, 1885

Subfamily Pleurocerinae Morrison, 19546

Genus Pleurocera Rafinesque, 1818

Species Pleurocera acuta™ Raf- inesque, 1831

Genus Goniobasis Lea, 1862

Species Goniobasis livescens

(Menke), 1830

Morrison (1952, 1954) in an evalua- tion of phylogenetic relationships of old and new world melanians, based on the morphology of the reproductive system and on biological considerations, sug- gested an arrangement in which all freshwater melaniids were grouped in 3 families, each of which is directly related to 3 marine families, as follows: 1) Melanopsidae-Modulidae; 2) Pleuro- ceridae-Cerithiidae; and 3) Thiaridae- Planaxidae. The first 2 groups are

SThe earlier family name Strepomatidae Haldeman, 1863, must be rejected because it is not basedon anavailable generic name. A proposal for validation and inclusion in the Official List of both the family Pleuro- ceridae and the genus Pleurocera as its type is now under the consideration of the International Commission of Zoological Nomenclature (Melville, 1960).

6Thiele (1929) listed Pleurocerinae as a subfamily of Melaniidae.

ТВу longstanding usage the species acuta has been treated as the type species of the genus Pleurocera, whereas, by strict application of the present rules of nomen- clature, the type species ought to be “P.” verrucosa. However, formal acceptance of verrucosa would entail confusing transfers of names; the snails now placed under Lithasia Haldeman, 1963, would become Pleurocera, while another name would have to be resurrected for those now commonly called Pleurocera. To avoid widespread confusion, a request for the validation of P. acuta as the type has been placed before the I.C.Z.N. (Melville, 1960).

dioecious, while no males are present in the third group, in which the females reproduce parthenogenetically. The families all belong in the superfamily Cerithiacea. Rosewater (1960a) con- siders the above proposals interesting but not yet conclusive and believes that some of the various relationships on which it is based need to be further investigated and evaluated before final acceptance.

According to Morrison the charac- teristics of the typical subfamily Pleuro- cerinae, to which the North American pleurocerids probably all belong, are: the females, all oviparous, unfailingly have an egg-laying sinus on the right side of the foot; the males have no intromittent organ.

Morrison, rejecting the name Pleuro- cera. for the forms grouped under it by Bryant Walker (1918), selected for them the name Oxytrema Rafinesque, 1819, and further combined under this genus, on the basis of egg-laying characters, most species of Goniobasis. He also revived the genus Mudalia Haldeman, 1840 and, placed Goniobasis livescens (Menke) under it.

The writer feels that the evidence for this combination and the concomitant transfers is as yet insufficient and prefers to maintain the traditional nomenclature until such a time when more extensive study of the group con- cerned will provide a broader basis for revision.

For further details on the subject the reader is referred to the section “Discussion of Pleurocerid Systematics” (p 71). In the following, a brief his- torical review only is given of the early literature pertaining to Pleuroceridae to provide a background. The earliest known pleurocerid records were those by Lister (1770) and Gmelin (1791) on Buccinum (-Goniobasis) virginicum. In the early days all the pleurocerid groups were assigned to the genus Melania Lamarck (1792), which also included all operculate fresh-water gastropods other than those belonging

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PLEUROCERA AND GONIOBASIS 9

to the Viviparidae and Pilidae, from all parts of the world. In due time the heterogeneous condition within the genus Melania was recognized and various authors provided some relief by splitting the group and introducing new genera. In the following are listed some of the most notable authors of generic names for the pleuroceridgroup of North America and their corres- ponding contributions. C. S. Rafinesque, in 1818, established the genus Pleuro- cera, naming 6 species without giving any descriptions; in 1819 he defined Pleurocera and created the genus Oxy- trema. The following year he described the first recognizable species, Pleuro- cera verrucosa (-Angitrema verrucosa) and at the same time he also described a species from Lake Erie, P. acuta. Rafinesque’s failure to designate a type for the genus Pleurocera has caused contention, not only among his contem- poraries, but also among many of his successors (Walker, 1917) and the ques- tion as to which species will ultimately be accepted as the type species is not yet settled. In 1819 he also named the genus Leptoxis. According to Morrison (1945) Leptoxis is the earlier and valid name for the genus that Thomas Say named Anculosa in 1821. Isaac Lea? later proposed the 3 genera: Jo, in 1831, Goniobasis, in 1862 and Eury- caelon, in 1864; Shuttleworth, in 1845, described the genus Gyrotoma; Halde- man, in 1840, named the genera Muda- lia, and Lithasia; Nitocris was named by H. and A. Adams in 1854. Pilsbry, in 1910, added the genus Lithasiopsis”.

H. and A. Adams (1854) established Elimia as a subgenus of Pleurocera

8Lea also introduced Trypanostoma (a syno- nym of Pleurocera) and Strephobasis as one of its sections, but these are not in use to- day.

2The position of this genus is dubious. I share Goodrich’s (1942) opinion that Lithasi- opsis probably is related to Pachy- chilus.

and placed in it 16 species including G. livescens; but among these were at least 4 with obviously different kinship (Goodrich, 1945). In 1896, Pilsbry tried to revive Elimia, raising it to generic rank, to take the place of Goniobasis. Later, he decided that Goniobasis should be restored as a genus on the grounds that Elimia was a composite group (Walker, 1918). The earlier synonyms for the genus Pleuro- cera are given in Tryon’s (1873) manual on the Strepomatidae, p 49, while those for the genus Goniobasis are listed on p 138.

Among authors that have made valu- able contributions to pleurocerid syste- matics are: Hannibal, Conrad, Anthony, DeKay, Hinds, Gould, Tryon, Menke, C.C. Adams, Goodrich, and others. Their contributions are too numerous to be discussed here; however, Adams’ study on Jo is listed in the references.

More detailed data on the literature regarding the 2 species under consid- eration, Pleurocera acuta and Goniobasis livescens, and their close relatives, will be given in the appropriate sections. Unfortunately these records deal mostly with descriptions of the shell and with ecology, while information on the ana- tomy and life history of these snails is scarce. Most important among these are Magruder’s (1935b) studies on the anatomy of Pleurocera canaliculatum undulatum which furnished a valuable basis for the present study and will be extensively quoted below. Worthy of note are also the studies of Rose- water (1959a, 1961) on P. canaliculata, those of the cytologist Woodard (1934, 1935, 1940) on the reproductive system and spermic dimorphism of Goniobasis laqueata and Jewell’s (1920) observa- tions on the reproduction of Goniobasis livescens correcta.

DISTRIBUTION

Geologic Distribution.

Records exist for pleurocerids in

10 B. C. DAZO

strata ranging from the Cretaceous to the Pliocene epoch. Although Weatherby (1876) suggested that they appeared as early as the Carboniferous age of the Paleozoic era, or that immediately suc- ceeding it, this has never been cör- roborated. White (1882), Walker (1900), and Adams (1915) were of the opinion that the earliest fossil Pleuroceridae are from the late Mesozoic Laramie formation, while Henderson (1935), in a comprehensive work on the nonmarine Mollusca of North America places them a little earlier. He reported that the oldest known member of this group is Goniobasis multicarinata Russell, which was found in Alberta, and which is believed to have existed during the Lower Cretaceous. He listed other fos- sil pleurocerids as follows: 13 species from the Upper Cretaceous, 10 from the Lower Cretaceous, and 28 from the Cenozoic (Tertiary) era.

The species Goniobasis livescens and Pleurocera acutum tvactum were reported by F. C. Baker (1902) from the Pleistocene loess. The oldest fos- sil specimen of G. livescens, according to F. C. Baker (1920), was found in the Toleston deposits of glacial Lake Chicago, whereas the oldest P. acuta (quoted as P. subulare (Lea) were from the Wabash and the Sangamon inter- glacial deposits. Wright (1932) studied post-glacial fossil remains of P. acuta and G. livescens in the Tippecanoe River system of Indiana and his find- ings indicated that they had migrated there from the Kankakee and Iroquois Rivers at the close of the glacialperiod. At present, the Tippecanoe system is a tributary of the Wabash River and a portion of the Ohio River drainage sys- tem, where these snails still flourish.

Two conflicting ideas exist with regard to the geographic origin of the living members of this group. The first and more popular theory supports the view that the Pleuroceridae originated from the Laramie formation (probable beds in Colorado, Wyoming, Montana, Alberta, and Saskatchewan). Their surviving des-

cendants are believed to have migrated from the west to the Mississippi Valley and southeastern United States together with the Unionidae. This theory was propounded by White (1882) who reasoned that although the large lakes, which existed in the Tertiary and Laramie periods, successively became obliter- ated, it was reasonable to conclude that at least part of the river channels of today have existed as such from earlier geologic times. This applies to some of the present tributaries of the Mis- Sissippi River system that partly coin- cide with former outlets or inlets, or both, of these ancient lakes. It is pos- sible, therefore, to infer that the mol- luscan fauna of the Mississippi River system descended directly from the faunae of those ancient lakes and mi- grated through the river systems in which they constituted lacustrine elements. Simpson (1896) accepted this theory.

The opposite view tends to support the idea that pleurocerids originated in the southeastern United States and that they spread westward, as they did during more recent post-glacial migrations (Walker, 1900). Adams (1915) favored this theory, stating that the southeastern streams have been favorable as habi- tats for certain mollusks since the close of the Paleozoic era. The presence of a large number of endemic species which are confined to that region strengthens his view. He postulated that the lack of fossils in the south- east was brought about by the persis- tent adherence of rivers to their ancient channels; it is only in deposits of lacus- trine portions of ancient river systems that these faunal elements have been preserved.

Geographic Distribution.

Lake Erie is the type locality for Pleurocera acuta. Its general distri- bution (Fig. 1) includes the headwaters of the Ohio River and its tributaries, the Mississippi River westward to eastern Nebraska and Kansas. The

PLEUROCERA AND FONIOBASIS 11

species invaded the Erie Canal and en- tered the basin of the Hudson River. According to F. C. Baker (1928a) the

easternmost locality record for P. acuta

is a tributary of Lake Champlain in Vermont, in the St. Lawrence drain- age; the most northern locality recorded is Lake Superior, Bayfield, Bayfield County, Wisconsin. Some forms, in- distinguishable from P. acuta, have been taken as far south as the branches of the Cumberland and Duck Rivers of Tennessee (Goodrich, 1940) and the tributaries of the Mississippi River in Louisiana and Arkansas.

Goniobasis livescens is generally dis- tributed from New York to the Great Lakes region, and from Canada to the Ohio River drainage (Fig. 2). It was named and described by Menke in 1830, from specimens collected from the eastern end of Lake Erie. It is found in the tributaries of the Ohio River, east of the Scioto River in Ohio, the Wabash River and its tributaries west to the Illinois River; it is especially common in the St. Lawrence River basin, including the Great Lakes. G. livescens occurs as far east as Lake Champlain and parts of Quebec. It also invaded the Hudson River Basin by way of the Erie Canal. It has been found in all of the Great Lakes except Lake Superior though it is known to occur in one stream tributary to Lake Superior and within less than a mile of the stream’s discharge; it oc- curs also in the St. Mary’s River con- necting Lakes Superior and Huron. In the Ohio River drainage it occupies small streams of western Pennsylvania and various rivers in Ohio, excepting the Scioto and the Little and Big Miami. Somewhat the same discontinuous dis- tribution is found in Indiana where G. livescens lives in streams flowing into Lake Michigan, in the Lake Erie drain- age and the Wabash River with its northern tributaries; it has not been found in the White River forks, nor in streams to the east of the Wabash, such as the Big Blue and White Water

Rivers. Specimens were reported from Des Moines River in Iowa by Goodrich (1940). Baker (1928a) stated that in Wisconsin С. livescens is confined to Lake Michigan and streams emptying ato it: The distribution of G. livescens in Michigan, based on studies by Goodrich (1945), is shown in Fig. 3 and the recorded distribution of P. acuta in Fig. 4. It is evident from these maps that G. livescens has a wider distribution in this state than does P. acuta. Goodrich (1940) further stated that it had a wider distribution in Michigan than any other aquatic mol- lusk, with the possible exception of the pulmonate, Helisoma trivolvis Say).

METHODS AND TECHNIQUES

Sampling Methods.

This investigation was begun with a general survey for areas positive for pleurocerid snails. Various collecting sites were chosen in Michigan (and also Ohio). For ecological and life history studies, 4 permanent stations were designated in 2 rivers and 2 smaller streams near Ann Arbor, Michigan, which are described in detail in the Ecology section (p 41).

These stations were visited at least once a month for a period of 1 year. The snails were collected by 2 methods: random sampling outside of the im- mediate station area and quantitative Sampling in staked areas.

In this second method, 3 one-meter quadrat samples were taken at each monthly collection, 2 samples on each side of the stream and the third in the middle. In order to avoid col- lecting in the same place, successive monthly samples moved progressively to an up-stream undisturbed portion.

The quadrat area was staked by using 4 strips of tin-aluminum metal alloy (each measuring 3 cm by 100 cm), with holes drilled at each end. Iron nails 6 inches long were driven through the holes, marking the square meter

12 B. C. DAZO

enclosure. The tin-aluminum alloy is heavy, sinks readily in water, and can be clearly seen. The metal strips also have the advantage of being easily rolled and stored when not in use.

All snails visible within the sample area through a glass-bottom viewer, were removed with a pair of forceps. Then the surface sand and gravel were carefully scraped and shoveled into a clean wooden box the bottom of which was lined with fine (about 1 mm) wire mesh for collecting the tiny snails. Occasionally, when the snail density was high only 1/2 or 1/4 of the quadrat was sampled.

Most of the snails recovered in the field were taken to the laboratory where they were relaxed and fixed (see p 14- 15). Some were crushed on the spot with a pair of pliers and fixed immedi- ately in Lavdowsky’s Solution (Formalin- Alcohol-Acetic Acid 2:10:1 parts by volume) to preserve the stomach con- tents for a study of the food habits of these snails (see p 64).

Shell measurements were made for use in a growth and life history study (p 63 and Table 12). The data re- corded were: (1) maximum length of shell; (2) greatest width perpendicular to the long axis; and (3) the number of whorls present. Larger snails were measured with calipers, whereas an ocu- lar micrometer and a dissecting micro- scope were used on the smaller ones. In all cases, measurements were taken with the aperture of the snail facing the observer.

The sex of the snail was also deter- mined (see p 63 and Table 13).

Limnological Methods.

Just before collecting snails at each permanent station during the monthly sampling, and at other collection sites limnological and other ecological obser- vations were made. The data taken include: free carbon dioxide content of the water, methyl orange alkalinity, dissolved oxygen, pH, water current velocity, water level fluctuations, tur-

bidity, and temperature records of both the water and the atmosphere. Lim- nological methods followed are those presented in Welch (1948) and in the “Standard Methods” of the American Public Health Association (1955). Ambient and water temperature were taken with an ordinary mercury ther- mometer. Water level fluctuations were recorded as follows: a wooden post was driven into the stream bed in the middle of the stream and, using this post as reference, the water depth was recorded at each visit. A portable Beckmann pH meter (Model 180) was used for determining the hydrogen-ion