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JANUARY 27, 1977 



Vol. 91 
No. 1 

A quarterly 

devoted to 

malacology and 

the interests of 


Founded 1889 by Henry A. Pilsbry. Continued by H. Burrington Baker. 
Editor-in-Chief: R. Tucker Abbott 



Dr. Arthur H. Clarke, Jr. 
Department of Mollusks 
National Museum of Canada 
Ottawa, Ontario, Canada K1A-0M8 

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 
Biological Laboratory 
National Marine Fisheries Service 
Oxford, Maryland 21654 

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 MoUusks 
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 
duseum of Zoology 
/he 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 Biology 

School of Marine and Atmospheric Science 
1 Rickenbacker Causeway 
Miami, Florida 33149 

Dr. Charles B. Wurtz 
3220 Penn Street 
Philadelphia, Pennsylvania 19129 


Dr. R. Tucker Abbott 

Delaware Museum of Natural History 
Box 3937, GreenvUle, Delaware 19807 

Mrs. Horace B. Baker 

Business and Subscription Manager 

1 1 Chelten Road 

Havertown, Pennsylvania 1 9083 


Delaware Museum of Natural History 

Kennctt Pike, Route 52 

Box 3937, Greenville, Delaware 19807 

Second Class Postage paid at Wilmington, Delaware 

Sut)scrlptlon Price: $7.00 (see inside back cover) 



Volume 91, Number 1— January 27, 1977 


Raymond W. Neck 

Geographical Range of Praticolla griseola (Polygyridae, Correction and Analysis 1 

David Nicol 

Geographic Relationship of Benthic Marine Molluscs of Florida 4 

William F. Gale 

Growth of the Fingernail Clam, Sphaerium transversum (Say) in the Field 

and Laboratory Experiments 8 

Eileen H. Jokinen 

The Formation and Structure of the Shell Varix in Stagnicola elodes (Say) 

(Gastropoda: Lymnaeidae) 13 

WiUiam H. Gilbert and Ellen F. Suchow 

Predation by Winter Flounder (Psevdopleuronectes amerkanus) on the 

Siphons of the Clam, Tellina agilis 16 

Dee S. Dundee and Anna Paine 

Ecology of the Snail, Melanoides tuberculata (Miiller), Intermediate Host of the 

Human Liver Fluke (Opisthorrhiii sinerms) in New Orleans, Louisiana 17 

Joseph C. Britton and Clifford E. Murphy 

New Records and Ex;ological Notes for Corincvla manilensis in Texas 20 

Elizabeth V. Gardo 

Opisthobranchs Found Off Little Egg Inlet, New Jersey, with Notes on Three 

Species New to the State 23 

William G. Lyons 

Notes on Occurence of Eupleura sulcidentata Dall (Gastropoda: Muricidae) 28 

Henk K. Mienis 

North American Land Snails in Israel 30 

S. K. Raut and K. C. Ghose 

Effect of Upwardly-directed Shell Aperture on the Aestivating Land Snail, Achatina fuiica 31 
Ralph W. Taylor and Clement L. Counts, III 

The Asiatic Clam, Corbicula manilensis, as a Food of the Northern Racoon, Procyon lotor 34 

Obituary of Allyn Goodwin Smith (1893-1976) 37 

Publications received 7 

Book review: (of) S. van der Spoel 36 

CULATION (Required by) Act of October 23, 1962: Section 
4396 Title 39. United States Code, and postal regulation 




Titleof publication: THE NAUTILUS 

Date of filing, September 25, 1976. 

Frequency of Issue: Quarterly (4 per year). 

Location of known office of publication: Delaware 

Museum of Natural History. Kennett Pike, Box 3937, 

Greenville, De. 19807. 

Location of the Headquarters of General Business 

Offices of the Publishers: Delaware Museum of 

Natural History, Kennett Pike, Box 3937, Greenville, 

De 19807. 

Names and addresses of publisher, editor, and 

managing editor: Publisher, Mrs. Horace Burrington 

Baker, 11 Chelten Rd., Havertown, Pa. 19083. Editor, 

R. Tucker Abbott, Delaware Museum of Natural 

History, Box 3937, Greenville, De. 19807. Managing 

editor, none. 

Owner: Mrs. Horace Burrington Baker, 11 Chelten 

Rd., Havertown, Pa. 19803. 

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C. M. Yonge and T. E. Thompson 


Two distinguished British marine biologists have combined their knowledge and talents to 
produce a compact, well-rounded account of the largest marine group of animals. 

"The first modem book on the biology of marine moUusks 
that is of textbook quality, yet so beautifully written 
and illustrated that the legions of amateur conchologists 
will readily absorb its wealth of information"—/?. Tucker 
Abbott, Ph.D. 

Send check or money order to: 
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Greenville, De. 19807 U.S.A. 

Available March 1977 

Clothbound, 288 pp., 162 text figures, 16 plates with 18 glorious color photographs of living 
marine molluscs. Only $13.9.5. 

Vol. 91(1) 

January 27, 1977 




Raymond W. Neck 

Texas Parks & Wildlife Department 

John H. Reagan Office Bldg. 

Austin, Texas 78701 

The geographical range of Praticolella griseola (Pfeiffer) in Texas and Mexico is 
discussed; erroneous but published collecting sites are discussed. The climatic 
causes of the discontinuity of geographic range of the species are discussed. 

Three species of Praticolella von Martens 
(Polygyridae) occur in Texas: pachyloma (Menke), 
berlandieriana (Moricand) and griseola (Pfeiffer). 
Early records placed griseola over much of 
southern and central Texas; these records were 
later corrected only to be subsequently 
republished. In light of the reoccurrence of 
this misinformation, all literature records are 
reconsidered and the geographical range of 
griseola is re-evaluated. Mexican and Central 
American records of this species are also discussed. 

Confusion of the range of griseola is no doubt 
due to a lack of definite phenotypic breaking 
points between griseola and berlandieriana even 
though the classic types are quite different. Some 
workers have felt that these two species definite- 
ly blend together (von Martens 1892; Singley 
1893) while others such as Pilsbry (1940:695) felt 
that there were "no common links" between 
them. Genitalia of berlandieriana and griseola 
are similar but distinguishable (Webb 1967). A 
definitive solution to the taxonomic problem wall 
be difficult to obtain and may be impossible due 
to contemporary habitat destruction. Adding to 
the complexity is the possibility of hybridization 
involving all three species in southern Texas 
(Hubricht 1961; in Cheatum and Fullington 1971). 

The first published records of P. griseola that I 
have found are those of Binney (1885:394) for 
Calhoun (at Indianola) and Bosque Counties. 
Townsend (1897) reported it on the "lower Rio 
Grande." Pilsbry (1940:690-692) completely dis- 
counted the Bosque County record and doubted 
the Indianola record. P. griseola is native in 

neither county. Pilsbry gave the range of griseola 
as "environs of Brownsville" which is in Cameron 

In the first synthesis of Texas molluscan 
records, J. A. Singley (1893) reported griseola 
from the following counties: Caldwell, Cameron, 
Duval, Gillespie, Goliad, Gonzales, Kendall, 
Milam (from Askew); Lampasas (from Mrs. 
Sinks); Williamson (from Walker); Bexar, Comal, 
Hays, Travis (Strecker's personal records). 

In the next compilation of Texas snail records, 
J. K. Strecker (1935) reported specimens in his 
collection from Cameron and Hidalgo Counties. 
He stated that "all other counties Singley men- 
tions for P. griseola are no doubt based on P. 
berlandienana" except Duval County. No reason 
was given for acceptance of the Duval County 

The latest compilation of Texas polygyrid snail 
records (Cheatum & Fullington 1971) re-publishes 
the suspect records of Singley with no mention of 
the intervening correction by Strecker. No men- 
tion is made, however, of the records of Binney. 
Significantly, all post-Singley records listed by 
Cheatum and Fullington come from Cameron and 
Hidalgo Counties in south Texas along the Rio 
Grande River. 

Thus, we are left with positive records for only 
two counties for griseola in Texas. Personal col- 
lecting in most of the central Texas counties has 
revealed no populations of griseola. I have per- 
sonal records from Brownsville (southern 
Cameron County) and Laguna Atascosa Wildlife 
Refuge (northeastern Cameron County). Webb 


January 27, 1977 

Vol. HI (1) 

(1967) worked with griseola collected at Harl- 
ingen (central Cameron County) by J. Campbell. 
Such a restricted Texas range for land snails is 
not unique, as Euglandina texasiana (Pfeiffer) 
and Thiisdiinphiira plaginpt i)cha (Shuttlewnrth) 
exhibit similar distributions. These snails in 
Texas are restricted to soils of the modem delta 
of the Rio Grande River which includes southern 
and eastern Hidalgo County, all of Cameron 
County and most of Willacy County. Shells of 
griseola have not yet been repwrted from Willacy 
County although the Laguna Atascosa locality is 
no more than thirteen kilometers from the 
Cameron-Willacy county line. Shells collected by 
Ideker in Willacy County in 1974 included no 
definite griseola shells although some berlan- 
dieriana shells from this area may indicate in- 
trogression with griseola. Populations of gyiseola 
are to be expected in southern Willacy County. 

The south Texas populations of g-riseola are 
isolated from Mexican populations (except for 
those in the southern Rio Grande delta) which oc- 
cur no further north than the Tampico area at the 
border between Vera Cruz and Tamaulipas. Other 
populations occur at scattered localities in north- 
ern Yucatan, Guatemala and Nicaragua (Rehder 

Other populations have resulted from introduc- 
tions. McLellan (19.50) reported griseola (could it 
have been berlandieriana?) to be abundant in his 
yard and adjacent lots in Bellaire, Harris County, 
Texas. Other adventive populations include Cuba 
(probably from Vera Cruz) and Key West, 
possibly from Cuba (Pilsbry 1940:642). 

The disjunction of populations of griseola is 
similar to the dry lowland tropical Gulf Arc 
distribution as exhibited by several species of 
reptiles and amphibians (Martin 1958:92-94). 
Herptile migration between these areas may have 
occurred via a dry corridor through presently wet 
tropical woodland areas at some time in the 
Pleistocene. The occurrence of the Texas popula- 
tions of griseola indicates a northward extension 
of its normal range. At some time in the recent 
past grifiPola apparently existed over large areas 
of coastal Central America, Mexico and (at least 
southern) Texas. 

Environmental change may have resulted in 
widespread extinction of griseola, with survival 

occurring only in a few scattered refugia. The 
restriction of griseola in Texas to the relatively 
mesic deltaic soils of the Rio Grande River in- 
dicates that increased aridity was the en- 
vironmental factor involved. The area between 
the Rio Grande delta and the Panuco River 
floodplain (Tampico area) contains only one 
significant drainage system. The floodplain of the 
Rio Soto La Marina in Tamaulipas should be ex- 
amined for populations of griseola. Although the 
entire area is arid, these rivers provide suitable 
moisture as a result of periodic flooding. The 
decline of griseola may have been accompanied 
by an expansion of berlandieriana, as the latter 
species occurs (possibly sparingly) in the area 
between the Rio Grande River and Rio Soto La 
Marina (Rehder 1966). A similar range disjunc- 
tion in northeastern Mexico is exhibited by the 
Texas pocket gopher (Selander et al. 1962). 

The second break is apparently not due to 
aridity. On the contrary, the break below Vera 
Cruz may result from excess moisture in the 
humid forest of the Campeche Lowlands. This 
area exhibits higher temperature, rainfall and 
humidity levels than either bordering area which 
contains griseola (Vivo E. 1964), Competition 
from tropical snail species specifically adapted to 
warm, moist habitats may exclude griseola. 

Much additional field work on geographic and 
habitat distribution of griseola is needed before a 
definitive answer to the reasons for range 
fragmentation and existence of particular refugia. 
It is difficult at best to correlate the distributions 
of organisms with compilations of environmental 
data from the literature. The refugia of griseola 
apparently represent areas of varied vegetation, 
geological and climatic regimes (Leopold 1950; 
Wagner 1964; West 1964; Vivo E. 1964). Alter- 
nate wet-dry cycles could be important because 
Webb (1967) indicated such conditions were 
necessary for the culture of both griseola and 

Fragmentation of the species range of griseola 
would be favorable for genetic differentiation be- 
tween refugia. This has, apparently, occurred as 
Rehder (1966) reported "P. griseola consists of a 
number of more or less well-characterized races" 
which he based on shell characters. 

Vol. 91(1) 

January 27, 1977 


One additional factor may be involved in the 
spotty distribution of griseola. A number of 
workers have suggested that griseola is not native 
to Yucatan and Guatemala (Bequaert & Clench 
1936; Harry 1950). All Guatemalan material (see 
Goodrich & van der Schalie 1957) was probably 
collected within a 20 km radius of each other ac- 
cording to Harry (1950); furthermore all Yucatan 
material collected by Harry (1950) definitely was 
from such a small area. These two centers of 
distribution are about 500 km apart. In these 
areas griseola is found exclusively in sites with 
orchards, railroad embankments, urban areas and 
savannahs managed for cattle grazing (see Be- 
quaert & Clench 1933; Goodrich & van der 
Schalie 1937). Basch (1959) did not find griseola 
in Tikal National Park, Guatemala. Other 
workers failed to find griseola when collecting in 
various parts of Guatemala and the Yucatan 
(Hinkley 1920: Pilsbry 1891; van der Schalie 1940). 
Stating that griseola is a species of open, rather 
than forested areas, Branson & McCoy (1963) felt 
that "man may augment the distribution of this 
form by his clearing activities, rather than ac- 
tually transporting it to new localities." 

Time and source of these putative introduc- 
tions into these southern areas are unknown. The 
existence of noticeable phenotypic types or 
"races" in the various areas of occurrence in- 
dicates the possibility of early introduction 
(pre-Conquest). Mayan and pre-Mayan set- 
tlements have existed in this area for centuries. 
Introduction of a limited stock (founder effect) 
and/or natural selection for individuals better 
adapted to local conditions would result in such 
genetic differentiation. The most likely source 
would be the Tampico-Vera Cruz populations, 
simply because of its close proximity. Branson & 
McCoy (1965) reported that specimens from 
Campeche were intermediate between Yucatan 
and Guatemalan material but closer to the 
Guatemalan specimens. 

The possibility of these populations being in- 
troduced to southern Texas is a strong possibility. 
Although almost all areas of the southern tip of 
Texas have been cleared or overgrazed at some 
time in the past century, griseola does not appear 
to be particularly associated with human impact 

areas. One would not expect a snail from tropical 
Mexico to flourish in natural habitats of sub- 
tropical Texas. Frosts occur in most years and 
hard freezes are not unkown. Additionally, long 
periods of dryness accompanied by high temper- 
atures are common in this area. A number of 
foreign snails have become established in this 
area (Neck, R. W. 1976). These snails, however, are 
generally restricted to human -associated sites. 


Basch. P. F. 19.59. Land molluscs of the Tikal National Park. 

Guatemala. Mas. Zoot. Univ. Mich. Occ. Pap. 612: 1.5 pp. 
Bequaert, J. C. and W. J. Clench. 19,33. The non-marine 

mollusks of Yucatan. Carnegie Inst. Wash. Pub. 

Bequaert, J. C. and W. J. Clench. 1936. A second contribution 

to the moUuscan fauna of Yucatan. Carnegie Inst. Wash. 

Pub. 457:61-75. 
Binney, W. G. 1885. A manual of American land snails. Bidl. 

Branson. B. A. and C. J. McCoy. 1963. Gastropoda of the 1961 

University of Colorado Museum expedition in Mexico. The 

Branson, B. A. and C. J. McCoy. 1965. Gastropoda of the 1962 

University of Colorado Museum expedition in Mexico. Univ. 

Colo. Stud. Ser. Biol. 13:16 pp. 
Cheatum, E. P. and R. W. Fullington. 1971. The Recent and 

Pleistocene members of the gastropod family Polygyridae in 

Texas. Bull. Dallas Mus. Nat. Hist. 1(1):74 pp. 
Goodrich, C. and H. van der Schalie. 1937. Mollusca of Peten 

and North Alta Vera Paz, Guatemala. Univ. Mich. Mus. 

Zool. Misc. Pubt. 34:.50 pp. 
Harry. H. W. 1950. Studies on the nonmarine mollusca of 

Yucatan. Mus. Zool. Univ. Mich. Occ. Pap. 524:34 pp. 
Hinkley. A. A. 1920. Guatemala mollusca. The Nautilus 

Hubricht, L. 1961. Eight new species of land snails from the 

southern United States. The Nautilus 75:26-32. 60-63. 
Leopold. A. S. 1950. Vegetation zones of Mexico. Ecology 

von Martens, E. 1892. Land and fresh-water molluscs. 

Bioldgia Centrali-Americana. 708 pp. 
Martin. P. S. 1958. A biogeography of reptiles and amphibians 

in the Gomez Farias region, Tamaulipas, Mexico. Mus. Zool. 

Utiiv. Mich. Misc. Pub. 101:102 pp. 
McClellan. J. H. 1950. Texas snails. The Nautilus 64:41. 
Neck, R. W. 1976. Adventive land snails in the Brownsville. 

Texas aLTea.Southwestem Nai uralist 21: 133-135. 
Pilsbry, H. A. 1891. Land and fresh-water mollusks collected 

in Yucatan and Mexico. Pr(x. Adad. Nat. Sci. Phil, for 

Pilsbry, H. A. 1940. Land mollusca of North America (north 

of Mexico). Monoy. Acad. Nat. Sci. Phil. (3): vol. 1, pt. 2. 


January 27, 1977 

Vol. 91(1) 

Rehder, H. A. 1966. TTie non-marine molluscs of Quintana 

Roo, Mexico, with the description of a new species of 

IMfmaeus (Pu!monata:Buiimulidae). /Vw. BioL Soc. Wash. 

van der Schalie. H. 1940. Notes on mollusca from Alta Vera 

Paz, Guatemala. Mxis. Zool. Univ. Mich. Orr. Pap. 413:11 pp. 
Selander. R. K.. R. F. .Johnston, B. .J. Wilks and G. G. Raun. 

1962. Vertebrates from the barrier islands of Tamaulipas. 

Mexico. Univ. Kan. Pub. Mus. Nat. Huit. 12:309-.34.5. 
Singley, J. A. 189.3. A preliminar>' list of the land. 

fresh-water, and marine mollusca of Texas. Fourth Annual 

Rep. Geol. Survey Tex. (1892), Contri. Nat. Hist. Tex. Part 

Strecker, .J. K. .Jr. 193.5. Land and fresh-water snails of Texas. 

Trans. Tex. Acad. Sci. 17:4-44. 
Townsend, C. H. T. 1897. On the biogeography of Mexico and 

the southwestern United States. II. Thins. Tex. Acad. Sd. 
2(1): 33-86. 

Vivo E., J. A. 1964. Weather and climate of Mexico and Cen- 
tral .America. In Natural environment and early cultures 
(R. C. West. ed.). Handbook of Middle American Indians 

Wagner, P. L. 1964. Natural vegetation of Middle America. In 
Natural environment and early cultures (R. C. West, ed.). 
Handbook of Middle American htdians 1:216-264. 

Webb, G. R. 1967. Erotology of three species of Pratieolella, 
and ofPolygifra pustula. The Nautilus 80:133-140; 81:11-18. 

West. R. C. 196^1. Surface configuration and asscx-iated 
geology of Middle America. In Natural environment and 
early cultures (R. C. West, ed.). Handbook <f Middle 
America Indians 1:43-83. 



David Nicol 

Box 14376, University Station, 
Gainesville, Florida 32604 


The geographic distributions of 1,137 species of benthic marine molluscs of 
Florida were analyzed. The number of Floridian endemics i'; 110, and those species 
not ranging north of Cape Hatteras is 159. The number of boreal or arctic species 
that range southward to Florida is only ki. Some species have migrated easticard 
to Florida along the Gulf Coast, and these number 158. The majority of Florida's 
benthic molluscs appear to have originated in the Caribbean region, and these 
species number 779 or 68.i percent of all the species analyzed. 

The gastropods have a higher percentage of species endemic to Florida (12. 7 per 
cent) as compared to only 3.6 per cent of all the species of pelecypods. and the 
pelecypods aymmonly have a higher percentage of geographically wide-ranging 
species than the gastropods. 

Florida probably has the most diverse marine 
shallow-water molluscan fauna in the con- 
tinental United States. Because of this, it has 
long been a favorite site for shell collectors, and 
the molluscs have been thoroughly described by 
malacologists. Certainly one of the reasons for 
the richness of this molluscan fauna is the fact 
that Florida is surrounded by warm shallow 
water, and the Florida Keys are less than two 
degrees north of the Trupic of Cancer. The 
powerful Florida Current sweeps between Cuba 
and the Florida Keys and can easily carry 

planktonic larvae of Caribbean species north- 
ward from Florida to Cape Hatteras, North 

In order to show the close relation.ship of the 
Caribbean and Floridian molluscan faunas, the 
geographic distributions given in two molluscan 
faunal monographs were analyzed: Abbott's 
American .'<eashplls (second edition, 1974) and 
Warmke and Abbott's Caribbean .^eashrlls 
(1961). Only the distributions of the benthic 
gastropods (mainly prosobranchs), the 
pelecypods, the scaphopods, and the 

Vol. 91(1) 

January 27, 1977 


polyplacophorans were studied. Species living at 
depths of 200 metere or more were largely 
eliminated because they commonly were known 
from only one or two dredging stations. The 
sample of molluscs analyzed included 750 
species of gastropods, 335 species of pelecypods, 
30 species of scaphopods, and 22 species of 
polyplacophorans. The total number of species 
analyzed was 1,137. 

The derivation of Florida's benthic marine 
molluscan species can be summarized by 
grouping them into four categories of 
distribution: (1) species probably originating in 
Florida and Floridian endemics; (2) species ex- 
panding their range southward to Florida along 
the Atlantic Coast or those mainly of boreal or 
arctic origin; (3) species expanding their range 
eastward in the Gulf of Mexico to Florida; (4) 
species expanding their range northward to 
Florida from the Caribbean region. These are 
the categories shown in Table 1. 

TABLE 1. Derivation of the benthic molluscs of Florida. 


N'l I'J. species Pi'r cent 

Species originating in Florida 
or Floridian endemics. 



Species migrating southward 
along the Atlantic Coast 



Species migrating eastward 
along the Gulf of Mexico 



Species migrating northward 
from the Caribbean region 






The number of endemic species, those con- 
fined to Florida, is 110. This comprises a sur- 
prising 9.7 per cent of all of the molluscs whose 
distributions were studied. Besides the species 
that are Floridian endemics, there are a few 
that are limited to the region extending from 
Florida to Cape Hatteras. Most of these 
probably originated in Florida and have ex- 
panded their range northward. The number of 
species that have this limited geographic 
distribution is 49, or only 4.3 per cent of all of 
the molluscan species studied. K one combines 
the number of Floridian endemic species with 
those that have a limited range from Florida to 

no farther north than Cape Hatteras, the per- 
centage of the total fauna in these two classes 
is 14 per cent. 

The number of boreal or arctic species that 
also live in Florida, commonly in moderately 
deep water, is only 42, or 3.7 per cent of the 
total benthic fauna. Most of these species range 
as far north as New England and eastern 
Canada and some even have a circum-boreal 
and arctic distribution. Some of these boreal 
and arctic species that reach Florida are 
Solemya velum Say, Nitcula proxima Say, 
Niwulana acuta (Conrad), Limopsis cristata Jef- 
freys, Limnpsis minuta Philippi, Argopecten 
uradians (Lamarck), Limatula subauriculata 
(Montagu), Astarie crenata subequilatera Sower- 
by, Tlujasira tiisimiata Orbigny, Hiatella arctica 
(Linne), Calliostoma bairdii Verrill and Smith, 
Crepidula fomicata (Linne), Urosalpinx cinerea 
(Say), Anachis lafresnayi (Fischer and Bernardi), 
and Ilyanassa obsoleta (Say). 

Some of Florida's molluscs are probably im- 
migrants from the Gulf Coast that migrated 
eastward into Floridian waters. The number of 
these species is 158 or 13.9 per cent of the total 
fauna analyzed. 

The majority of the molluscs of Florida ap- 
pear to have had a Caribbean or West Indian 
origin. These species number 779 or 68.4 per 
cent of all of the species studied. Many of these 
species range as far north as Cape Hatteras, 
but some are found only in the Florida Keys. 
Some of these Caribbean species range as far 
north as Cape Canaveral on the east coast of 
Florida, and a few live as far north on the 
west coast of Florida as Tampa Bay. The mol- 
luscan fauna of Florida has been enriched by 
many tropical genera from the West Indies 
such as: Astraea, Nenta (four species each), 
Strombus (five of six species), Triiia (seven 
species), Cypraea (five species). Cassis (three 
species), Cymatium (eleven species), Tonna (two 
species). Bursa (six species), Mitrv, (five species). 
Area (two species), Barbatia (four species), 
Isognomon (three species), Pinctada (one 
species), Spondylus (two species), Lima (three 
species), Chama (six species), Pseudochama (one 
of two species), and Asaphis (one species). There 
are a few notable exceptions to the rule that 


January 27. 1977 

Vol. 91 (1) 

m(jst genera and species originated in the West 
Indian area. One of these is the genus Busycon. 
with five species living in Florida, and none 
found in the Caribbean region proper. Other e.x- 
ceptions are Dinocardium robu.'itum (Lightfoot) 
and Scaphella junonia (Lamarck). 

Waller (1973. p. 32) states that the West In- 
dian character of the moUuscan fauna of Ber- 
muda has long been known. Many species of 
molluscs of Caribbean origin are found in 
Florida and also Bermuda. It appears that 
almost all of the non-endemic molluscan species 
of Bermuda were derived from the Caribbean 
region. The distribution maps presented by 
Warmke and Abbott (1961) are most helpful in 
obtaining some idea of the distribution of the 
molluscs of Florida. These distribution maps 
clearly show that many of the benthic marine 
molluscan species came to Florida from the 
Caribbean region. For the Florida Keys and 
much of peninsular Florida, more than two 
thirds of the molluscan species came from the 
Caribbean area. 

'Riere are some striking differences in 
geographic distribution when one compares the 
ranges of the gastropods, pelecypods. 
scaphopods, and polyplacophorans with one 
another. There are at least two main factors 
that influence the differences among these four 
classes of molluscs. One is the type of sub- 
strate; whether the bottom consists of soft 
sediments, which is ideal for burrowing or in- 
faunal animals, or whether the substrate is 
rockj', which is ideal for epifaunal animals. The 
other factor is the mode of reproduction. Are 
eggs and sperm simply released into the water 
and the eggs fertilized and followed by a long 
free-swimming larval stage as. for example, most 
pelecypods? Or is fertilization commonly internal 
and with a short free-swimming larval stage or 
none at all as, for example, in many gastropods? 

The comparison of the scaphopod and 
polyplacophoran distributions is an example of 

TABLE 2. Species endemic to FJimda 

Cla^.t Size of sample No. of species Percent 






95 12.7 

12 ae 

1 3.3 

2 9.1 

two groups that occupy different types of sub- 
strates. The fX)lyplacophorans are found on a 
rock or hard shelly substrates or are epifaunal, 
whereas the scaphopods live partially buried in 
soft sediments, or are basically infaunal. In 
Table 4 one sees that five, or 16.7 per cent, of 
all scaphopod species appear to have migrated 
eastward into Florida along the Gulf Coast, but 
none of the polyplacophoran species has this 
distribution. Perhaps the lack of a rocky 
shoreline along much of the Gulf Coast has 
prevented species of polyplacophorans from 
moving eastward into Florida. As shown in 
Table 3. only one scaphopod species and no 
polyplacophorans appear to have a boreal or arctic 
origin. Table 2 shows that Floridian endemics are 
higher among the polyplacophorans. (two species 
or 9.1 per cent as compared to the scaphopods with 
one species or 3.3 per cent of thier total species. 
This higher rate of endemism among the 
polyplacophorans may be caused by the lack of 
a rocky shoreline in areas adjacent to Florida. 
The polyplacophorans have a higher percentage 
of species originating in Caribbean waters as 
compared to the scaphopods as shown in Table 
5. However, these differences between the 
scaphopod and polyplacophoran distributions in 
the latter three instances may not be 
significant because of the small sample sizes in 
these two classes of molluscs. 

TABLE 3. Species migrating southivard along the 
Atlantic Coast to Florida. 

Ga^ Size of sample No. of species Per cent 















TABLE 4. Species migrating ecustwat-d along the 
Gulf of Mexico to Floiida. 


Size of sample Xo. of species Percent 












TTie pelecypods have a higher percentage of 
infaunal species and also a higher percentage of 
species that have a free-swimming larval stage 

VoJ. 91 (1) 

January 27, 1977 


TABLE 5. Species migrating northtmrdfrnm the 
Caribbean region to Florida. 

(IfLss Size o/Saviple No. of species Percent 

















than the benthic gastropods. The latter factor 
is probably the main one as to why the 
gastropods have a much higher percentage than 
the pelecypods (12.7 per cent as compared to 3.6 
per cent) of endemic species. This marked dif- 
ference in endemic species is seen in Table 2. 
However, some of the apparent greater amount 
of endemism among the gastropods may be 
because there are many smaller-sized species of 
gastropods than pelecypods and because of this, 
their geographic distributions are less com- 
pletely known. Some of the gastropod species 
that Abbott (1974) states are endemic to 
Florida are species of small size, 10.0 mm or 
less. This does not explain all of the difference 
in amount of endemism between the gastropods 
and the pelecypods, and it is generally true that 
the pelecypods in the Floridian fauna have a 
higher percentage of wide-ranging species than 
the gastropods. This comparison between the geo- 
graphic distributions of benthic pelecypods and 
gastropods should be made in other regions to see 
if it holds true everywhere because of its 
significance to biostratigraphy. 

The type of substrate is probably the main 
factor that causes pelecypods to have 17.3 per 
cent of their species migrating eastward along 
the Gulf Coast into Florida as compared to 
only 12.7 per cent of all of the species of 
gastropods. This difference is seen in Table 4. 
As seen in Table 3, the pelecypods also have a 
higher percentage of species of boreal or arctic 
origin, 6.3 as compared to 2.7 per cent among 
all gastropod species. The fact that a higher 
percentage of the pelecypods are infaunal as 
compared to the gastropods is probably the 
main factor because as Thorson (19-57) has faint- 
ed out, the diversity of infaunal sf)ecies in- 
creases little from the polar regions to the 
tropics, but the diversity of the epifaunal 
species increases greatly from the polar regions 
to the tropics. The percentage of pelecypod 
species and gastropod species migrating from 
the Caribbean region to Florida is nearly iden- 
tical. This is shown in Table 5. 


Abbott, R. T. 1974. American seashells. 2nd. ed., Van Nos- 

trand Reinhold Co., New York, 663 p. 
Thorson. G. 1957. Bottom communities (sublittoral or shallow 

shelf), in Treatise on marine ecology and paleoecology. 1 

Ecology, Geol. Soc. Am. Mem. 67, p. 461-.534. 
Waller, T. R. 1973. The habits and habitats of some Ber- 

mudian marine mollusks. The Nautilus 87(3): 31-52. 
Warmke, G. L., and R. T. Abbott. 1%1. Caribbean seashells. 

Livingston Publishing G)., Narberth, Penn., 346 p. (Dover 

Paperback. 1975). 


Tebble, Norman. 1976. British Bivalve Seashells. Edinburgh. 

212 pp. Second Edition. Evidently no changes, except for 

four previously black-and-white plates now being in color. 

This is really a second printing. 
Narchi, Walter. 1974. Functional Morphology of Petricola 

(Rupellarm) typica (Bivalvia; Petricolidae). Marine Biology, 

vol. 27, pp. 123-129, 9 figs. Excellent. 
Sandved, K. B. and R. T. Abbott. Sept. 1976. Shells in Color 

112 pp., 101 colored plates. Viking Penguin Books, 

Baltimore. Paperback, $4.95. 
Leathem, Wayne and Don Maurer. Oct. 1976. Phylum 

Mollusca: A Ouide to the Mollusca of the Delaware Bay 

Region 43 pp., mimeographed. Contains list, keys and 

bibliographies. $3.00. Publications Office, College of Marine 

Studies, Newark, De. 19711. 
Mayissian, S. 1974. Coquillages de No^ivelle-Caledonie et de 

Melanesie. 72 pp., 28 colored plates. Privately printed, S. 

Mayissian, Noumea. Sumptious. 
Lefevre, George and W. C. Curtis. 1912 (1976 reprint). Studies 

on the Reproduction and Artificial Propagation of 

Freshwater Mussels. Bull. Bureau Fish., vol. 30, for 1910. 

Softback reprint by Aurele La Rocque, Columbus, Ohio. 

Pojeta, John Jr. and Bruce Runnegar. 1976. T^e Paleontology 
of Rostroconch Mollusks and the Early History of the 
Phylum Mollusca. U.S. Geol. Survey Prof. Paper 968, 88 pp., 
54 pis. $3.40. Four subphyla and eight classes of mollusks 
are recognized. New are two families, six genera and 18 
species in the fossil Rostroconchia. 

Colloque International de Malacologie Marine Appliqee. 1976. 
Haliotis, vol. 5, pp. 1-300. Research reviews on various aspects 
of conchyliculture, pollution and commercial shellfisheries 
in Europe. 

Abbott. R. Tucker. 1975. Muscheln and Schnecken des Meeres. 
Delphin Verlag, Stuttgart. German translation of Golden 
Nature Guide, 1962. 

Chen. T. P. 1976. Aquaculture Practices in Taiwan. 162 pp., 98 
figs. Fishing News Books, Ltd., Surrey, England £2. Covers 
culture of oysters, Meretrix, Anadara and Corbiatla, as well 
as fish and frogs. 

Dance, S. Peter. Nov. 1976. TTie Shell Collector's Guide, An In- 
troduction to the World of Shells. 192 pp., 34 color pis., text 
figs. Entertaining and well-done beginner's guide to con- 
chology. David and Charles, London. 


January 27, 1977 

Vol, 91(1) 


William F. Gale^^ 

Department of Zof)logy and Entomology 
Iowa State University, Ames, Iowa 50010 


Field and laboratoi-y experiments on Pool 19 of the Mississippi River in summer 
and fall of 1967 revealed that S. transversum can complete its life cycle in about a 
month or less. In laboratory experiments, many newborn clams entered a resting 
state and did not grow for 33 days after they were bom; later, some grew large. 
Medium-sized clams grew slowly but gave birth to young that often grew faster 
and larger than their parents. In field experiments, clams that were moved from 
an open-river site (where the clam poptdation was high) to a retainer in a cove 
(ivhere the population was low) grew faster and became larger than those remain- 
ing at the collection site; they also grew larger than clams in laboratory ex- 

Fingernail clams were abundant in Pool 19 of 
the Mississippi River during a 1966-68 survey of 
the benthos. Densities of Sphaerium transversum 
reached over 100,000/m' in some areas (Gale, 
1969) in spite of heavy predation by leeches, fish, 
and waterfowl. In autumn of 1967, diving ducks 
harvested about 24% (2,085,125 kg) of September's 
standing crop of fingernail clams (Gale, 1973; 
Thompson, 1973). Life history data were collected 
in an effort to determine the cause of the clam's 
success. The objective in this study was to deter- 
mine how fast S. transversum grows. 


Growth experiments were conducted during the 
summer and fall of 1967. Laboratory experiments 

' Journal Paper No. J-7982 of the Iowa Agriculture and 
Home Economics Ejcperiment Station, Ames, Iowa. Project 
1373. A contribution from the Iowa Cooperative Fishery Unit 
sponsored by the Iowa State Conservation Commission. Iowa 
State University of Science and Technology, and the Fish and 
Wildlife Service (U. S. Department of the Interior) (Contract 

' Present address: Ichthyological As.sociates, Inc.. Berwick. 
Pennsylvania 18603. 

' I thank Dr. Kenneth D. Carlander and Dr. R. Jess Muncy. 
of the Department of Zoolog>' and Entomology, Iowa State 
University, who directed the research and made many helpful 
suggestions concerning the manuscript. 

were conducted in a field laboratory above Ft. 
Madison, Iowa (about 200 m upstream from the 
Ft. Madison/Niota bridge). Water pumped from 
near the river channel into the laboratory kept 
temperatures and chemical conditions similar to 
those in the river and provided clams with food. 

Clams were housed in individual plexiglass 
rearing chambers, 3.8 cm square and 5.0 cm deep 
inside (Fig. 1, A); the upper 3.3 cm of the 
chambers were covered on two sides with plastic 
screen (mesh with 12 openings/cm) for water 
passage. A set of nine rearing chambers was 
placed in each of nine painted plywood compart- 
ments (Fig. 1, B). A 5-cm baffle kept water levels 
about 6 mm below the top of the rearing 
chambers. Clams could not escape or move be- 
tween chambers without crawling out of the 

Each rearing chamber contained about 10 cc of 
strained clayey silt from the river bottom where 
experimental clams were collected. Water in the 
chambers was initially 3.5 cm deep but decreased 
to about 2.5 cm as chambers silted in. Compart- 
ments holding the chambers had a maximum 
flush rate of 6 minutes; fluctuating pump 
discharge and partial clogging of distribution tub- 
ing reduced flushing rate. 

Vol. 91(1) 

January 27, 1977 




41 CM 

(" ( ' r ' r ' r ' r' r ' 








42 CM 








FIG. 1. Rearing apparatus. A, set of nine rearing chambers 
(side view). B, compartment ivith rearing chambers in place 
(top view). 

TABLE 1. Reproduction and growth o/S. transversum in chambers in the laboratory between 21 July and 23 August. 1967. and 
numbers present on November 7.5. 

One large (over 10.0 mm long), two medium 
(4.0-6.0 mm long) or four small (newborn) clams 
were randomly assigned to each chamber; each 
compartment had three chambers of clams of 
each size group (chamber identification numbers 
were adjusted for presentation in Table 1). Large 
and medium-sized clams were collected in the 
river, but small clams were born in the 
laboratory. Small clams were removed with 
camel-hair brushes (Thomas, 1959) within an hour 
after their birth in pans of river water and 
measured with an ocular micrometer. Larger 
clams were measured with a vernier caliper; 
damaged clams were discarded. Similar sized 
clams were used as chambermates so that mark- 
ing was unnecessary and handling was 

The laboratory growth experiment began July 
21, 1967; after 33 days, 3 units were removed, the 
27 chambers cleaned, and the contents screened. 
Clams were measured as before and living ones 
returned to their respective chambers (Table 1) 
with fresh substrates. 

To measure clam growth in the field, two re- 
tainers with 80 clams each were submerged in 
the river on July 6. One retainer was put in a 
sheltered cove adjacent to emergent and 

July 21 

August 23 

November 15 


No- per 



No. broken 
in handling 

No, with 
no growth 

Lengths of those 
which grew (mm) 

No Length 

Livinp Dead 












100 22 








2 1.4 

13 9 







1 1.8 

22 7 










76 1.6-6.0 

170 65 








53 1.6-9.0 

237 .32 

Chambers 7 and 8 were treated the same as 1-6 and 9, but are listed separately since the clams showed reproduction and more 
growth. The clams with shells broken in handling on August 23 had not grown, nor had the dead clams in 1-6 or 19-27, but five 
in 10-18 had grown 0.1 to 2.6 mm and one showed no growth. 


January 27, 1977 

Vol. 91 (1) 

submergent vegetation (transect 5 station 2 of 
Gale, 1969, p. 11) where there were less than 1,000 
clams/m^; the other was placed in open water 
(transect 4 station 14 of Gale, 1969, p. 11) where 
there were about 42,000 clams/m^ 

Each retainer (Fig. 2, A) held 40 rearing tubes 
(Fig. 2, B) suspended through holes in a plex- 
iglass plate by aluminum rods. Rearing tubes 
were 7 to 8 cm lengths of polyvinylchloride pipe 
(I.D. 2.5 cm) with plastic screen attached near the 
bottom: a painted wooden disk closed the lower 
end of the screen. A tube like that in Figure 2, C 
could be constructed and cleaned more easily. 

Two randomly selected clams 5-7 mm long and 
10 cc of strained clayey silt from station 14 were 
placed into each tube. The retainer was then 
forced into the river bottom until the two plex- 
iglass flanges on the sides halted penetration 
with the rearing tubes just above the substrate. 

The retainer at station 2 was removed on 
September 6. It had been turned over and many 
tubes nearly filled wath mud. Tube contents were 
screened and the clams counted and preserved in 



FIG. 2. Rearing apparatus used in maintaining S. transver- 
sum in the field. A, clam retaining apparatus: B, enlarged 
side view of a rearing tube used in 1967: C, rearing tube with 

10% buffered formalin. Buoys marking the re- 
tainer at station 14 disappeared by September, 
and the retainer was lost. 

Clam Growth in the Laboratory 

Although the nine large clams stocked in 
chambers 19-27 died shortly after the experi- 
ment started, 53 young, 1.6-9.0 mm long 
(Table 1), were produced (some may have been 
second generation offspring). In only 33 days, 
or less, one of the offspring had grown approx- 
imately 7.0 mm in length (newborn clams in 
Pool 19 average 2.2 mm long) (Gale, 1969) to 
near maximum size.(S. transversum usually do 
not exceed 12.0 mm in Pool 19, but clams up to 
15.9 mm long and 8.1 mm thick were found.) 
Reproduction in chambers 7 and 8, where 
newborn clams had been stocked, demonstrated 
that S. transversum not only could grow large in 
a month but could complete its life cycle as well. 

Many newborn clams, stocked in chambers 1-9, 
had not grown by August 23 (Table 1) and some 
of them did not move for several minutes after 
removal from their chambers; some seemed dor- 
mant (in a resting state). The periostraca of the 
nongrowing clams were discolored and chalky. 

Most of the 12 medium-sized clams that sur- 
vived in chambers 10-18 grew slowly with a mean 
length increase of 1.3 mm. Clam growth in 
chamber 12 was not determined because five 
clams exceeded the initial size of parental stock 
and offspring and parents could not be 
distinguished. In most instances, offspring of the 
medium-sized clams grew rapidly and one was 9.0 
mm long. 

By November 15, when the chambers were 
reexamined, reproduction had occurred in all but 
two of the 27 chambers. Reproduction was max- 
imum in chambers where one large clam had 
originally been stocked (19-27) and one clam left 
79 descendants. Many of the clams that seemed 
dormant in August (chambers 1-9) had grovm to 
9.0 mm or longer (Fig. 3). Most of the clams 
stocked in chambers 10-18 had died without 
reaching 9.0 mm, and many were smaller than 
their offspring. Because observations of growth in 
chambers 28-81 did little more than confirm 

Vol. 91(1) 

January 27, 1977 


observations in chambers 1-27, precise data were 
not collected. 

In November the periostraca of nearly all 
clams longer than 2.5 mm were speckled with 
dark deposits and some were nearly black. S 
transversum usually seems very clean, and it is 
not known why deposits had accumulated on the 

Clam Growth in Field Experiments 

Clams grew well in the rearing tubes at station 
2, and after 62 days, 45 were 4.0 mm or more 
thick; the largest was 13.8 mm long and 6.6 mm 
thick. Clams in the tubes were larger than those 
living at station 14, the collection site (over 5,000 
clams were examined there in mid-September but 
none was 4.0 mm thick). That four clams in each 
of 2 tubes were over 5.0 mm thick means that 
within 62 days, one or both stocked clams grew to 
maturity and discharged young that also had 
grown large. 

Clams in the tubes contained many embryos 
and one large individual that seemed to have 
given birth to 35 young (its chambermate had 
died before reaching reproductive size) contained 
86 embryos. A few of the 35 young may have 
been second generation offspring. 

A specimen of Sphaerium striatinum, placed 
into a tube by mistake, had growm to a thickness 
of over 4.0 mm but had not given birth. 

Clams in 21 tubes were dead, perhaps from 
senility, leech predation, or other causes (Gale, 
1973). One live clam had a fungal growth nearly 
covering outer portions of the inner gill; embr>'os 
in the gill seemed unaffected. 


In laboratory and field experiments, S. 
transversum grew extremely fast and completed 
its life cycle in about a month or less. Rapid 
grow1;h has been noted for some other species of 
Sphaerium. Sphaerium partumeium grew large in 
7 to 10 weeks in laboratory experiments (Thomas, 
1965) and gave birth when less than 14 weeks 
old; clams grew even faster in the field. S. par- 
tumeium (as M. partumeium) reared by Krull 
(1936) grew to 4.5 to 5.0 mm long in about two 
months and gave birth. Sphaerium corneum, 
Sphaerium rivicola, and Sphaerium solidum 


FIG. 3. Length changes in small and medium-sized S. 
transversum in the laboratory, 1967. 

suspended in baskets in the Elbe River grew 
rapidly (Thiel, 1928, 1930), and some S corneum. 
born in early summer, matured, gave birth, and 
died that autumn. 

If S. transversum in the natural environment 
grew as rapidly as those in laboratory and field 
experiments, several generations could be pro- 
duced annually. At station 14, however, medium- 
sized clams seemed to have grown only 2 mm 
longer in July and 3 mm in August (Gale, 1972), 
considerably less than those in growth ex- 
periments. Clam grovrth may have been hindered 
at station 14 by high clam density. Also, the 
clams were probably debilitated by high infesta- 
tions of larval trematodes (Gale, 1973). 

Although clam growth rates in the laboratory 
and at station 2 were similar, clams grew much 
larger at station 2. Because parental stock of both 
groups came from the same site and presumably 
from the same genetic stock, some factor or fac- 


January 27, 1977 

Vol. 91(1) 

tors in the laboratory seem to have stunted the 
clams. Clams at some sites in the river did not 
reach ma.ximum size either. Thiel (1928) observed 
that 5. comeum in the Elbe River did not grow 
to maximum size in "overpopulated" areas. The 
fact that some medium-sized S. transvermm. 
which did not grow much during the first :33 days 
of the laboratory experiment, remained smaller 
than their offspring in November (Fig. 3), sug- 
gests that, once growth is arrested or retarded, it 
is not completely compensated for later, when 
growth conditions become favorable. 

Why some clams had initial growth lags and 
their chambermates did not is not clear, but 
delayed growth does not seem to have been 
genetically controlled (Gale, 1972). Delayed 
growth may involve metabolic slowdown that 
enables clams to bury themselves deep in the 
substrate to escape predation, parasitism, or un- 
favorable water conditions (Gale. 1973). In tem- 
porary ponds in Michigan, Kenk (1949) found 
that only fairly young Sphaerium ocddentale and 
S. partumemm (as S. truncatum) survived the 
dry period. 

It is sometimes pointed out that fast growth is 
of great advantage to inhabitants (such as some 
fingernail clams) of temporary ponds, because 
they can take advantage of a short growing 
period. One might conclude that, through evolu- 
tion and natural selection, the advantage of being 
able to survive short growing periods has pro- 
duced clams with tremendous growth rates. But, 
the fact that S. transversum grows rapidly but 
does not often inhabit temporary ponds, suggests 
that other factors produced rapid growth. This 
rapid growth may be a form of preadaptation. 
That S. transversum may have originated in tem- 

porary ponds and then moved to other habitats 
merits consideration. 

But, regardless of why S. transversum grows 
rapidly, the fact that it can complete its life cycle 
in about a month may be a major factor in its 
success in Pool 19, where predation pressures are 
great. If a population is to sustain itself under 
heavy predation, quick growth and reproduction 
would be advantageous, if not essential, for the 
shorter the prereproductive period, the greater 
the probability an organism has of reproducing 
before being consumed. 


Gale. W. F. 1969. Bottom fauna of Pool 19, Mississippi River 

with emphasis on the life history of the fingernail clam, 

Sphaerium transversnm. Ph.D. thesis. Iowa State Univ., 

Ames. Univ. Microfilm No. 69-20642. Ann Arbor. Mich. 
Gale, W. F. 1972. Seasonal variability in calyculism in 

Sphaerium transversum (Say). The Nautilits S6: 20-22. 
Gale. W. F. 1973. Predation and parasitism as factors affecting 

Sphaerium transversum (Say) populations in Pool 19, 

Mississippi River. Res. Popul. Ecol. 14: 169-187. 
Kenk. R. 1949. The animal life of temporary and permanent 

ponds in Southern Michigan. Misc. Publ Mus. Zioi. Univ. 

Mich. 71: ,5-66. 
Krull. W. H. 19136. Raising Musculium partumeium (Say) 

under laboratory conditions. Papers Mich. Acad. Sci. Arts, 

ami Letters 21: ^35-638. 
Thiel. M. E. 1928. Zur Biologie unserer Siisswasser-muscheln. 

Z Mnrphol Okol. Tiere 13: 65-116. 
Thiel. M. E. 1930. Untersuchungen liber den Einflti-ss der Ab- 

wasser von Hamburg-Altona auf die Verbreitung der Arten 

der Gattung Sphaerium in der Elbe bei Hamburg. Int. Rev. 

gesam. Hydrobiol. Hydrogr. 24: 467-484. 
Thomas. G. J. 19.59. Self-fertilization and production of young 

in a sphaeriid clam. The Nautilus 72: 131-140. 
Thomas. G. J. 1965. Growth in one species of sphaeriid 

clam. The Nautilus 79: 47-54. 
Thompson. .1. D. 1973. Feeding ecology of diving ducks on 

Keiikuk Pool. Mississippi River. Jmir. Wikil. Manage. 37: 


Vol. 91(1) 

January 27, 1977 





Eileen H. Jokinen 

Biology Department 
Suffolk University 
Boston, MA. 02114 


A life history study carried out in 1970-71 on a population of Stagnicola elodes 
in a temporary pond in lower Michigan reveals that a varix is laid damn at the 
cessation of a period of shell growth which may or may not be followed by a 
period of dormancy. The adult snails of the Michigan population have 2 varices, 
one deposited before estivation of the juvenile snail, the other deposited after adult 
spring growth. It appears that the number of varices cannot be used to estimate 
the age of the snails unless the annual life cycle and environmental conditions are 

The microstructure of the varix was determined by microscopic examination of 
acetate peels of shell sections made at right angles to the varix. The varix is 
fonned from greatly elongated (.5-6X normal) crystals of the prismatic layer. The 
probable function of the varix is to add strength to the outer lip. 


The freshwater snail Stagnicola elodes (Say) 
periodically puts down additional shell material, 
the varix (Baker, 1911), on the inside of the outer 
lip. In S. elodes the varix is purple-brown in col- 
or and parallels the outer lip. In Baker's opinion, 
varices, normally three in number in Lymnaea 
palustris ( = S. elodes), mark periods of "hiberna- 
tion" when the animal is "buried in 
mud" and do not represent annual growth mark- 
ings. However, Baker was not positive of this in- 

DeWitt (1954) reports that when "growth in 
Physa gyrina is interrupted for some reason, the 
inner edge of the outer lip of the aperture is 
strengthened by a triangular thickened band . . . 
Conditions which arrest growth and lead to for- 
mation of these bands are obscure; production 
does not appear to be dependent upon en- 
vironmental factors, rather they are a result of a 
physiological pattern developed within the species 
and perhaps modified to some extent by environ- 
ment." DeWitt states that the bands might be ac- 
counted for in terms of periodic drying of the 

habitat but felt it unlikely that such a thickening 
would be produced under adverse conditions of 
drought or estivation. Herrmann & Harman 
(1975) believe that varices in Helisoma anceps 
(Menke) reflect slow winter growth. 


During 1970-71 a study was carried out on the 
life history of a population of Stagnicola elodes 
(Say) in a woodland pond in the Pontiac Lake 
Recreation Area, Oakland County, Michigan. The 
annual life cycle begins in May when eggs are 
laid. Egg laying continues through July. The new- 
ly hatched generation feeds until the snails reach 
2-7 mm in length. At this point the young cease 
growth and actively leave the water to estivate 
on grasses and tree trunks above ground. The ma- 
jority of the older snails follow the receding pond 
water to become stranded on the dry pond floor 
and there be preyed upon, most commonly by 
sciomyzid (Diptera) larvae. The young estivating 
snails eventually leave their above-ground loca- 
tions and come to lie under the pond leaf litter to 


January 27, 1977 

Vol. 91(1) 

over-winter. TTie immature snails (mean shell 
length = 8 mm) become active in the spring as 
soon as the ice melts. The snails grow rapidly so 
that by June the mean shell length is approx- 
imately 15mm (Jokinen, in prep.). 

The snails of the Michigan population of S. 
elodes were noted to deposit several varices dur- 
ing their life times. In 1970, varices on the outer 
lips were first noted on July 12 on 4 snails (shell 
lengths from 10.3 to 21.7 mm) out of 123 (3.3%). 
Egg masses were in evidence by this date. By Ju- 
ly 26, 13 out of 121 snails (10.7%) had varices. On 
August 9, estivating immature snails were first 
observed and noted to have varices (100%). In 
1971, 5 snails were collected from under the ice 
in February and March. The snails ranged from 
3.7 mm to 11.8 mm and all 5 had varices on their 
outer lips. On April 20, 1971, 34 snails were col- 
lected. The winter varix was evident on all of the 
snails, and 32 had new, fragile, and thin shell 
growth beyond the varix. The mean linear incre- 
ment of new growth beyond the varix was 1.5 
mm (range .2-3.5 mm). Shell growth was rapid 
during May and egg masses appeared by the end 
of the month. By June 6, the entire sample 
population of 153 snails (except one) had 
deposited new varices. 


In order to determine the structure of the 
varix of S elodes, a portion of shell was cut at 
right angles to the aperture, so that the section 
was at right angles to the length of the varix 
(Figure 1). Acetate peels were made from 
polished shell sections following the method of 
Boardman & Utgaard (1964). 



FIG. 1. Locaticn of the varix in Stagnicola elodes (Say). 

FIG. 2A. Acetate peel of a polished shell section cut at right 
angles to the varix. The normal shell iMth i's demonstrated 
in the tipper portion of the photograph. The thicker portion is 
the varix. p., peroist racum : 1.1., longitudinal lamellar layer; 
c.1.1, first crossed lamellar layer; c.1.2, second crossed 
lamellar layer; pr., prisniatie layer. 

FIG. 2B. 7.5X magnification of the area between the arrows 
of A. There are two layers of periastracum and a space 
beneath the periostracum. p., periosiranim ; I.I., longitudinaJ 
lamellar layer; c.1.1, first crossed lamellar layer; pr. 
prismatk layer. (?50x total magnificatian). 

According to Boggild (1950), the calcareous por- 
tion of the shell of Stagnicola pitluxtriit (= S. 
elodes) is composed of aragonite deposited in four 
distinct layers. The shells of S. elodes from 
Michigan were examined and found to also 
possess four calcareous layers arranged as 
follows: (1) a very thin outer longitudinal 
lamellar layer under the periostracum; (2) a 
crossed lamellar layer; (3) a prismatic layer; and 
(4) a second crossed lamellar layer (Figure 2). As 
illustrated, the varix is formed by an increase in 
the length of the crystals of the prismatic layer. 
The crystals are approximately 5-6 times as long 

Vol. 91(1) 

January 27, 1977 


in the varix as in the normal shell. Gross ex- 
amination of a ground section demonstrates that 
the purple-brown color of the varix is due to 
streaks of pigment laid down in the thickened 
prismatic layer. The thickened outer lip of 
mature Helix IThebnl pisana MUller is also formed 
by elongated prismatic crystals (Matthes, 1914). 


Field evidence shows the pattern of varix 
deposition to be associated with cessation of 
growth. Snails without a varix were rapidly 
growing individuals, including the newly hatched. 
Snails with a terminal varix were estivating 
juveniles, overwintering individuals, and egg-lay- 
ing adults which had completed their spring 
grovrth. The varix is laid down at the end of a 
period of growth and not during a period of dor- 
mancy. Therefore, the number of varices cannot 
be used to estimate the age of snails unless the 
annual life cycle and environmental conditions 
are examined. 

The number of varices in adult snails will dif- 
fer, depending upon annual activity. If a pond 
dries up in summer, gains water again before 
temperatures become too cold for gastropod ac- 
tivity, and then warms up again the following 
spring, breeding adult snails will have 3 varices; 
two representing periods of pre-dormancy and 
one the termination of growth before egg deposi- 
tion. This is probably the situation observed by 
Baker (1911) who found 3 varices normal for L. 
palustris (= S. elodes), one varix on the third 
whorl, one on the fifth, and a third on the aper- 
tural lip of the adult. 

The snails from Michigan all had a varix inside 
the outer lip in early spring before the ice 
thawed. In this case the summer-fall estivation, 
marked by a varix on the juveniles, had con- 
tinued into the overwintering period, the pond 
not refilling until freezing temperatures had ar- 
rived. Therefore, the snails were not given the op- 
portunity to renew growth in the fall. After the 
pond thawed and the water warmed, new shell 
material was rapidly laid dovm, the pur- 
ple-brown color of the summer-fall varix mark- 
ing the initiation of dormancy. By June the 

snails had grovra considerably in length and the 
new shell growth was very thin. Then linear 
growth slowed, the new shell material thickened 
and another varix was deposited. Under such con- 
ditions an adult snail will exhibit only two 

Microscopic examination suggests that the 
varix adds considerable strength to the shell lip 
as is the case with the shell lamellae found in 
Biomphalaria (Richards, 1964). It is doubtful that 
the varix would protect against desiccation since 
it extends into the shell aperture only a short 
distance. A likely function would be to 
strengthen the shell lip and thus protect against 
breakage between f)eriods of growth, whether or 
not the snails are active. 


I wish to express my sincere gratitude to Dr. 
David R. Cook for his advice and encouragement. 
Dr. Osborn B. Nye for technical instruction, and 
Dr. Peter H. Rich for critically reviewing the 
manuscript. Preparation of the manuscript was 
aided by the facilities of the Biological Sciences 
Group at the University of Connecticut. 


Baker, F. C. 1911. The Lymnaeidae of North and Middle 

America, recent and fossil. Spec. Publ. No. 3. Chicago Acad. 

Boardman, R. S. & Utgaard, J. 1964. Modifications of study 

methods for Palezoic Bryozoa. J. Palemit. 38:768-785 
Boggild, 0. B. 1930. The shell structure of the mollusca. K. 

danske Vidensk. Selsk. Skr., Natunndensk. math. Afd. (9) 

DeWitt, R. M. 1954 Reproduction, embryonic development 

and growth in the pond snail Physa gyrina Say. TVans. 

Amer. Micros. Soc. 73:124-137 
Herrmann, S. A. & Harman, W. N. 1975. Population studies 

on Helisoma anceps (Menke) (Gastropoda: Planorbidae). 

Jokinen, E. H. (in prep). Estivation in Stagnicola elodes (Say) 

(Gastropoda: L>Tnnaeidae). 
Matthes, W. 1914. Beitrage zur Anatomie von Helix pisana 

Mull. Je«a Z. Naiiirwiss. 53: 1-.50. 
Richards, C. S. 1964. Apertural lamellae as supporting struc- 
tures in Australorbis glabrattis (Say). The Nautilvs 78: 



January 27. 1977 

Vol. 91 (1) 




William H. Gilbert > 

Department of Biology 

Colby College 
Waterville. Maine 04901 

and Ellen F. Suchow 

Belle W. Baruch Institute 

University of South Carolina 

Columbia, South Carolina 29208 

The bivalve Tellina agilis Stimpson commonly 
inhabits marine, shallowwater, sand-mud 
sediments (see Maurer, et ai, 1974). These small 
clams (max. length = 1.6 cm) burrow 1-3 cm into 
the sediment and deposit -feed on the sediment 
surface with separate, extensible, inhalent 
siphons (Gilbert, 1970), movements of which may 
attract visual predators such as the commercially 
important winter flounder, Psendopleuronedes 
americanus (Walbaum). Edwards, et al. (1970) 
have shown that small flounder, Pleumnectes 
platessa (L.), in Scotland obtain a large part of 
their food by preying on siphons of Tellina tenuh 
da Costa, which can regenerate their siphons. The 
aim of our study was to seek evidence that small 
winter flounder prey on siphons of T. agilis in 

Eight winter flounder (lengths = 4-6 cm) were 
collected (27 September 1969) at the mouth of 
Barnstable Harbor (Cape Cod Bay), 
Massachusetts. The fish were captured by hand 
net during the flooding tide on a sand flat 0.5 m 
above mean low water. An abundant population 
of T. agiUs (100-600/m^) occurred on the flat, but 
other clams with similar siphons (e.g., Cumingia, 
Macoma, and Petricola) were rare or absent (see 
Edwards, 1975). The fish were placed immediately 
in 95% ethyl alcohol to terminate digestion, and 
stomach contents were examined later in the 

Stomachs of four of the eight fish contained 1-3 
siphon fragments (9 total). These fragments and 
intact siphons of T. agilis collected at the site had 
similar measurements (made at 7X power with 
an eye-piece micrometer) for total width, width 
of circular muscle bands, and width of 

longitudinal bands (Fig. 1). The length of an ex- 
tended siphon is 3-4 times shell-length; the 
fragments ranged from 0.5-2.5 mm in length and 
were usually identifiable as the siphon tip. 

Levinton (1971; Levinton & Bambach, 1975) 
report that Macoma tenia (a subtidal clam) 
deposit-feeds on detritus at night when its 
siphons are not visible to fish predators, but that 
T. agilis deposit-feeds on benthic diatoms during 
the day. Many benthic diatoms concentrate dur- 
ing the day at the sediment surface, which turns 
a golden-brown hue as a result (Sanders, et al., 
1962). Thus the efficiency of daytime grazing by 
T. agilis may outweigh the hazard of exposing 
siphons to fish predators. 

In the laboratory, we observed the behavior of 
a small winter flounder placed in a water tank 
with a tray of sediment containing several live T. 
agilis. On two occasions, the fish uncovered clams 
by lunging at the sediment surface where siphons 
were deposit-feeding. When each clam attempted 
to burrow back into the sediment, the fish took a 
bite out of its foot. 

' Present address: Environmental Studies Program, Ottawa 
University, Ottawa. Kansas 66067. 

FIG. 1. Intact .-tiphim of a Tellina agilis (shell-length = 1.0 
cm) in .W/o ethyl alcohol. 

Vol.91 (1) 

January 27, 1977 


Martin (1940) reports that T. agilis (as T. 
tenera) is an intermediate host for Monorcheides 
cumingiae, a parasitic trematode which encysts 
(as metacercariae) in siphon and foot tissues of 
the clam. Martin fed infected clams to eels and 
flounders (species unspecified) and obtained adult 
Monorcheides later from intestinal mucusa of the 
fish. Our observation that small winter flounder 
prey on T. agilis suggests that these fish might 
take in Monorcheides. Further studies are needed 
to determine (1) whether or not winter flounder 
is a definitive host for this parasite, and (2) the 
importance of T. agilis siphons in the diet of 
young winter flounder. 

We thank Drs. D. C. Edwards, J. S. Levinton, 
and F. J. Vemberg for their comments about this 


Edwards, R. R. C, J. H. Steele, and A. Trevallion. 1970. The 
ecology of 0-group plaice and common dabs in Lock Ewe. 
III. Prey-predator experiments with plaice. J. Exp. Mar. 
fto/.£coU: 156- 173. 

Gilbert, W. H. 1970. Territoriality observed in a population of 
Tellma agilis (Bivalvia: MoUusca). Biot. Bvll 139:423-424 

Levinton, J. S. 1971. Control of tellinacean (Bivalvia: 
MoUusca) feeding behavior by predation. Limnol. Oceanogr. 

Levinton, J. S., and R. K. Bambach. 197.5. A comparative 
study of Silurian and Recent deposit-feeding bivalve com- 
munities. Paleobiology 1:97-124. 

Martin, W. E. 1940. Studies on the trematodes of Woods Hole. 
III. The life cycle of Monorcheides cumingiae (Martin) with 
special reference to its effect on the invertebrate host. Biol. 
Bull. 79:131-144. 

Maurer. D., L. Watling, and G. Aprill. 1974. The Distribution 
and Ecology of Common Marine and Estuarine Pelecypods 
in the Delaware Bay area. The Nautilus 88: 38-45. 

Sanders. H. L.. E. M. Goudsmit, E. L. Mills, and G. E. Hamp- 
son. 1962. A study of the intertidal fauna of Barnstable 
Harbor, Massachusetts. Limnol. Oceanogr. 7:63-79. 




Dee S. Dundee and Anna Paine 

Department of Biological Sciences 
University of New Orleans, Louisiana 70122 


The habitat and associates of a series of populations of the prosobranch snail, 
Melanoides tuberculata (Thiaridae) introduced to a drainage canal in New 
Orleans, Louisiana, are described. These snails, and associated fish, could serve 
as intermediate hosts of the Chinese Liver Fluke, Opisthorchis sinensis. 

In the spring of 1975, two populations of 
Melanoides tuberculata (Miiller) (Thiaridae) were 
discovered in New Orleans, one in the People's 
Avenue Canal, Orleans Parish, and the other in 
the canal on the neutral ground of General 
DeGaulle Drive, Jefferson Parish. A third popula- 
tion has recently been reported to us in 1975 
from the west Metairie canal in Jefferson Parish. 

This oriental prosobranch had previously been 
reported from two localities in Texas (Murray, 
1964; Murray and Wopschell, 1965), one in 
Arizona and another in Oregon (Murray, 1971). 
Abbott (1973) summarized its spread into Mexico 
at Vera Cruz and in Panama and Puerto Rico. 
The role of M. tuberculata as an intermediate 
host in the life cycle of the Chinese Liver Fluke, 


January 27, 1977 

Vol, 91(1) 





! 1 i I f 1 I ! 


FIG. 1. A portion of the New Orleans drainage system in rela- 
tion to the Peopk's Avenue carud. 

Opisthorchis sinensis, makes the occurrence of it 
in the U. S. of more than casual interest. 

This study was done in a section of People's 
Avenue Canal which is part of the New Orleans 
storm drainage system. Since this city is largely 
below sea level, drainage is accomplished by pump- 
ing stations at intervals in the drainage canal 
network (Fig. 1). This locality (Fig. 2) is per- 

manently supplied with slightly brackish water 
from a 600' well tapped by American Standard 
Co. for use as cooling water in their air condi- 
tioning system. 


The reported habitat of Melanoides tuberculata 
elsewhere in the U. S. is freshwater springs with 
a pH of 7.0-7.5, a water temperature of 18-25° C, 
and soft mud or gravelly-mud bottoms (Murray, 
1971). The People's Avenue habitat is similar to 
this. With few exceptions the stream bed is 50-70 
cm wide and 10-40 cm deep. The flow during the 
study was 42-51 cm/sec. Once we noticed a brief 
threefold flow increase, from an unknowoi source. 
At this time the level in the basin at the north 
end rose 20 cm in a five minute period. The non- 
vegetated bottom is sandy with scattered pebbles 
and shells of Ravgia cuneata, a brackish -water 
mactroid clam which is used for gravel. Few 
Melanoides are found in this type of bottom. 
Flow is much slower and the accumulation of silt 
and detritus much greater behind the overhang- 
ing stems and protruding roots of the bank 
vegetation. This seems to be the prime 
Melanoides microhabitat, supporting up to 251 
snails/sq. ft. (2700/m^). 

The canal banks are covered with vegetation. 
The predominant cover is a prostrate species of 
medium-height grass (probably Eragrostiit) with 
Tifpha and Lysimachia constituting most of the 
rest of the cover. The grass and Lysimachia are 












FIG. 2. Histogram shounng population aye groups in the spring of 1975. 

mill IIIL^iiiik.. 

Vol. 91(1) 

January 27, 1977 




■ ■■■ 

b rrggi 

1 ♦ 

2 X 






■ Ul^ 

• ••• 

3 A 

4 A 

5 X 

6 X 

7 X - 



■ III 

■ ■1 

■ III 

7AV I — 


n , smsh 



-> 8 X 

9 X 


10 A 

11 A 

■ ■■■ 

■ pipe IXIII 
■over canal ■ 

12 A 


E N 




scale in meters 




1 Eragrostis 
O Typha 

• Phragmites 
D Spartina 

♦ Gravelly 
X Soft mud 
A Sandy 



9 253 

10 140 

11 152 

12 16 

FIG. 3. Diaymm of People s Avenue Canal showiny di. 

the only plant species directly in contact with 
Melanoides. At the stream bank they create the 
sheltered environment that Melanoides seems to 
prefer. Other plants in the area are: Polygonum 
sp., Spartina altemiflora, Phragmites communis, 
and Sagittariafalcata. 

Animal species associated with Melanoides at 
this site include insects (Ranatra and Pelocoris, 
both predaceous hemipterans; Chironomidae, 
dipterans), crayfish, oligochaetes, and fishes 
(Poecilia latipina and Heterandria formosa). The 
fishes are of particular interest since various 
poecilids are known to be second intermediate 
hosts for Opisthorchis sinensis, the human liver 
fluke which has Melanx)ides tuberculata as its 
first intermediate host. 


Square foot (.093 m) quadrat samples were 
taken starting from the northernmost end of the 
canal (Fig. 3) at 46-meter intervals downstream 
(12 stations in all) to the point where the canal 
turns westward and goes underground. Two 
samples were taken at each station, at opposite 
banks just underwater and at the surface. In- 
dividuals were returned to the lab, counted, 
measured, and whorl counts made. Histograms 
were then plotted from these data for each sta- 
tion. The population for September-October 197.5 
follows a normal curve pattern with a few young 
of 10 mm and 8 whorls, a few older individuals of 
44 mm and 14.5 whorls, and the bulk of the 
population in-between. The best-represented size 
class is 25 mm long with 12 whorls. Fig. 2 is a 
histogram of the snail total lengths— lumping all 

Uribii tlon ofsnails in relation to substrate and vegetation. 

of the stations (656 individuals) to present an 
overview of the population. The histogram 
will doubtlessly shift considerably during 
reproductive seasons. Only one cluster of young 
was found indicating that late summer is not a 
major reproductive season for these live-bearers 
here. A parthenogenetic mode of reproduction has 
been reported tor Melanoides (Jacob, 1957). 

TABLE 1. The range of physico-chemical values encountered 
for each parameter. 



chlorides in ppt 



salinity in ppt 



dissolved oxygen in ppm 



free CO; in ppm 



phenolphthalein alkalinity ex- 

pressed as ppm CaCOj 



t»tal alkalinity expressed as 

ppm CaCOa 



Temperature (water) 






The flow from the well is 4500 liter/min. This 
water has some interesting properties related to 
its origin. The usual alkalinity values en- 
countered for Lake Pontchartrain are in the 
30-50 ppm range; free CO2 is generally less than 
5 ppm. At the pH values we recorded, carbonate 
ion is absent; the high CO2 and alkalinity values 
are what might be expected for a subterranean 
water source that is far from being in 
equilibrium with the atmosphere. The low 
dissolved oxygen content (saturation at 25° C is 
8.1 ppm) also suggests this water is recovering 
from subsurface conditions. All these water quali- 
ty parameters may have been affected by passage 


January 27, 1977 

Vol. 91 (1) 

through the American Standard Company air 
conditioning system. The slight brackishness of 
this water is usual for southeastern Louisiana 
waters and does not seem to inhibit Melanmdes. 


The introduction of Meldmildpn tuberrulntd in- 
to an area where poecilid fishes occur plus the 
fact that Vietnamese people are being settled 
nearby could be highly significant, particularly if 
some of these people are infected with trematodes 
and if they are still including raw fish in their 
diet. It is not known at the time of this writing 
whether the incoming Vietnamese were screened 
for liver flukes. Since all of the ingredients for 
the Opi.'^thorchut life cycle might now be present, 
it is important that we learn more about the 
snail and continuously monitor the spread of it. 


We wish to thank Dr. Harold Murray of Trini- 
ty University for verifying our determination of 

the snails. Voucher specimens have been 
deposited in the Delaware Museum of Natural 
History, No. 113847. Also the following Univer- 
sity of New Orleans graduate students were 
equally responsible for the results of this study: 
Bill Copeland, Tom Chin, Ben Garrett, Cheryl 
Noble, Mike Rayle and Mary St. Martin. 


Abbott. R. T. 1973. Spread of Melanmdes tuberculata. The 

.lacub. .J. 19.57. Cytological Studies of Melaniidae (Mollusca) 

with Special Reference to Parthenogenesis and Polyploidy. 

I. Oogenesis of the Parthenogenetic Species of Melanoides 

(Prosobranchia-Gastropoda). Trans. Roy. Soc. Edinburgh 

63: *1 1-3.52. 
Murray, Harold D. 1964. Tarebia granifem and Melanoides 

tuberculata in Texas, (an abstract). Ann. Reports Amer. 

Malacol. Union, 15-16. 
Murray, Harold D. 1971. The Introduction and Spread of 

Thiarids in the United States. The Biologist 53(3): 133- 135. 
Murray, Harold D. and Leon J. Wopschell. 1965. Ex»logy of 

Melanmdes tuberculata (Miiller) and Tarebia granifera 

(Lamarck) in South Texas (abstract). Ann. Reports Amer. 

Malacol. Union, for 1965, pp. 25-26. 


Joseph C. Britten and Clifford E. Murphy 

Department of Biology 

Texas Christian University, 

Fort Worth, Texas 76192 


Corbicula manilensis is distnbuted through seven major drainage systems in 
Texas. Potential mechanisms of dispersal are discvssed. The species seem to prefer 
sandy substrates in Texas reser^wirs but occm's in a variety of bottom types. 
Specimens of Corbicula have been removed from stomachs of three species of 
yis/i— Lepomis microlophus, Minytrema melanops and Aplodinotus grunniens. 

The first reports of Corbicula manilensis in 
Texas were from the western portion of the state 
(Metcalf, 19(56 and Metcalf and Smartt, 1972). 
Murray (U)71) discusses the presence of Corbicula 
in S(juth Texas and notes its eastward progres- 
sion from the Rio Grande drainage to Lake Cor- 
pus Christi, 25 miles north of Corpus Christi. He 

also reports large populations of the Asiatic clam 
from Lake LBJ in the Colorado River drainage of 
Central Texas (Murray, 1972). 

Corbicula was reported in Ijouisiana waters as 
early as 1961 (Dundee and Harman, 1963). Con- 
sidering its rapid range expansion in other parts 
of the United States, it is interesting that no 

Vol. 91 (1) 

January 27, 1977 


reports of Corbicula in eastern Texas have yet ap- 
peared in the literature. It seems inevitable, 
however, that the eastern and western popula- 
tions of Corbicula will finally converge in this 

We have compiled a list of new distributional 
records of Corbicula in central, northeastern and 
eastern Texas. The first record of the species in 
northeastern Texas was from Lake Grapevine 
(Tarrant County), a reservoir of the upper Trinity 
River drainage. Mr. Donnie Roberts provided the 
senior author with several specimens collected 
from Lake Grapevine in November, 1972. Subse- 
quently, several reservoirs in Tarrant County 
were found to harbor Corbicula populations. The 
authors recovered specimens from Lake Arlington 
on January 21, 1974; from Lake Benbrook on 
February 3, 1974; and from Eagle Mountain Lake 
in September, 1974. In August, 1973, the senior 
author collected a specimen from the Colorado 
River at Marble Falls in central Texas. 

During October and November, 1974, and 
March and April, 1975, the Texas Christian 
University Research Foundation provided finan- 
cial support which enabled us to briefly survey a 
number of Texas reservoirs east of the Colorado 
River system. We visited Possum Kingdom 
Reservoir (Brazos River drainage). Lake Play 
Hubbard, Navarro Mills Reservoir, C«dar Creek 
Reservoir, and Lake Livingston (Trinity River 
drainage). Lake Conroe (San Jacinto River 
drainage). Lake Tawakoni (upper Sabine River 
drainage). Diversion Lake, Lake Wichita, and 
Lake 0' the Pines (Red River drainage), and 
Lake Sam Rayburn and Steinhagen Reservoir 
(Neches River drainage). Most of the surveys 
were not exhaustive (exceptions were those at 
Possum Kingdom, Diversion Lake and Lake 
Wichita) so the failure to detect Corbicula at a 
locality does not necessarily indicate the absence 
of the species in an area. In fact, only Lake Sam 
Rayburn and Lake Texoma yielded specimens. 
The Rayburn specimens were collected from a 
sandy substrate on the northwestern shore of the 
lake on October 18, 1974, whereas specimens from 
Lake Texoma were taken from sand along the 
northern shore of the lake near the University of 
Oklahoma Biological Station on April 24, 1975. 

Harold Murray has provided additional 
distribution data from central Texas. He has 
received specimens collected by Emily Mims from 
Lake Buchanan on June 30, 1973. On September 
21, 1973, the ecology class of Trinity University 
recovered Corbicula from Canyon Lake, 
Guadalupe River. Scott Horn provided Murray 
with specimens collected on September 8, 1974, 
from the Guadalupe River below the dam at 
Highway 90 and 90A near Seguin, Texas. 

Ray Dinges of the Texas Water Quality Board 
has provided us additional records. He has col- 
lected Asiatic clams from Lake Austin on the 
Colorado River, along the Colorado River between 
Austin and Bastrop, and in the Nueces River 
along Texas Farm Road 1025, north of Crystal 

The known distribution of Corbicula in Texas 
now includes seven major drainages: the Rio 
Grande, Nueces, Guadalupe, and Colorado Rivers, 
with dispersal apparently occurring within these 
systems generally from west to east, the upper 
Trinity River drainage and the Red River 
drainage with populations recruited from an 
uncertain source, and the Neches River drainage 
with this population possibly recruited from 
Louisiana (see Figure 1). Considering the ap- 
parent lack of Corbicula populations immediately 
adjacent to the upper Trinity River assemblage, 
it seem possible that the species gained access to 

FIG. 1. The knoum distribuiion of Corbicula manilensis in 
Texas through April 1975. 


January 27, 1977 

Vol. 91 (1) 






T T 





T T 



































FIG. 2. Size frequency di.ftrihulidii of a nindom sample nf 
paired rnlres of Corbicula manilensis collected from Lake 
Benhrook. Texas. November. l!)7Jt. 

North Texas waters as a result of introduction 
from a remote source. Many live-bait 
establishments obtain minnows from Arkansas or 
Louisiana, transporting several hundred gallons 
of water with each shipment of minnows. 
Perhaps Corbicula larvae may have been 
transported with this water. Fisherman could 
just as likely bring an establishing population in- 
to the area in a live-bait hold of a boat. The pat- 
tern of distribution of Corbicula in Texas is 
decidedly trending along a roughly north to south 
axis. This fact may be due only to coincidence, 
but since it parallels closely a migratory bird 
flyway, it may suggest an alternative dispersal 

From whatever source that Corbicula became 
established in Tarrant Cbunty reservoirs, it is 
certain the Asiatic clam is firmly entrenched 
there. In 1973, Britton, Murphy, Keith and 
Mauldin completed a study of the bivalve fauna 
of Tarrant County Reservoirs. From June 1971 to 
August 1972, extensive bivalve collections were 
made in Benbrook and Eagle Mountain reser- 
voirs. At that time there was no evidence of Cor- 
bicula in either lake. By November 1974, shell 
debris accumulations of Corbicula along portions 
of the western shore of Benbrook Lake yielded 
densities in excess of 800 valves per foot. A ran- 
dom sample of 140 paired valves was taken from 
this shell debris material. Measurements were 
made of each individual in the sample. The 

length of the largest was 30.4 mm. A frequency 
distribution of length or height measurements ob- 
tains a distinctly bimodal curve, suggesting two 
major age classes among the Benbrook Corbicula 
population (Figure 2). This correlates well with 
the time available for the species to have become 

Considering the rapid spread of Corbicula in 
southwestern Texas and among the Tarrant 
County reservoirs, it is interesting that the 
species apparently has not yet entered the Brazos 
River system (or, at least the upper Brazos from 
Possum Kingdom Reservoir to Waco, Texas). In 
the summer and fall of 1974, we made extensive 
collections of bivalves from Possum Kingdom 
Reservoir during a period when the lake was 
significantly below normal. Corbicula was never 
observed. In addition, Mr. Chuck Fontainer has 
been intensively studying unionid populations in 
the Brazos River near Waco. He has employed 
numerous collecting techniques including SCUBA 
diving to recover clams. To date he has not en- 
countered Corbicula in the Waco area. The 
Brazos drainage should be monitored closely dur- 
ing the next few years, as it is the only major 
river system between western and eastern Cor- 
bicula populations which still lacks the species. 

The substrate preferences of Corbicula in Texas 
are variable. We have taken the species from san- 
dy gravel, sandy mud and muddy sand, and from 
deeper water muds. The most abundant popula- 
tions seem to be on or in sandy or muddy sand 
substrates. Clams can be found on the surface of 
the substrate or buried as much as two cen- 
timeters below the surface. At Sam Riiyburn 
Reservoir we found a population of Corbicula in 
a muddy sand substrate. The clams were approx- 
imately 2 cm below the surface, but produced a 
hole which emerged at the sandy water-substrate 
interface for water currents to enter the mantle 
cavity. The origin of this tube is curious, as the 
siphons of Corbicula are too short to be extended 
2 cm to the surface to produce it. Although we 
have tried to reproduce the situation with 
laboratory specimens, we have not been suc- 

The largest concentrations of Corbicula have 
been collected from shore to depths of about 8 

Vol. 91 (1) 

January 27, 1977 


feet. Living specimens have been recovered by 
dredging in silty substrates in Lake Benbrook at 
a depth of approximately 20 feet. 

Our students have removed Corbicula from 
stomachs of three fish species from North Texas 
waters. A red ear sunfish, Lepomis microlophuii, 
from Lake Benbrook was found to contain Cor- 
bicula shells up to 5 mm in length. A spotted 
sucker, Minytrema melanops. from the same lake 
had ingested shells up to 3 mm in length. From 
Eagle Mountain Lake a freshwater drum, 
Aplixiinotus gmnniens. had five specimens of 
Corbicula in the gut ranging from 3 to 5 mm in 


Britton, Joseph C. C. E. Murphy, D. E. Keith, and Virginia 

Mauldin, 1973. A quantitative and (jiialitative survey of the 
plankton and benthic invertebrates including bivalves of 
Eagle Mountain and Possum Kingdom Lakes Part III, 
Bivalves Texas Electric Service G)mpany Research Report 
178. 101 pp. 

Dundee, D. S. and W. J. Harman. 196."!. Oirbicula fluminea 
(Mailer) in Louisiana. The Nauiduii 77(1): 30. 

Metcalf. Artie L., 1966. Corbicula manilensia in the Mesilla 
Valley of Texas and New Mexico. The Nautilus 80(1 ): 16-20. 

Metcalf, Artie L. and Richard Smartt, 1972, Records of in- 
troduced mollusks: New Mexico and western Texas. The 
A^aM/i7«s 85(4): 144-145. 

Murray. Harold D., 1971. New records of Corbicula manilensis 
(Philippi) in Texas. The Nautilux 85(1): 3.5-36. 

Murray. Harold D.. 1972. Freshwater mussels in Lake LBJ, 
Te.\as. Bulletin of the American Malacological Union for 
1971, pp. .36-37. 

Sinclair, Ralph M., 1971. Annotated bibliography on the exotic 
bivalve Corbicula in North America. 1900-1971. Sterkiana 
43: 11-18. 


Elizabeth V. Carlo 

Ichthyological Associates, Inc. 

Box 70-D, R. D. 2, West Brook Lane 

Absecon, New Jersey 08201 


An intensive ecological survey in the incinity of Little Egg Inlet, New Jersey 
found three species of opisthobranchs which are new to New Jersey (Pleurobran- 
chaea tarda, Onchidoris bilamellata, and Facelina bostoniensis) and southern 
range extensions for Dendronotus frondosus and Tergipes tergipes. The occurrence 
of cold water opisthobranchs in New Jersey is explained in part by ocean water 
temperatures which rarely exceed 25°C, by the numerous submerged artificial 
structures, and by the predominant southwest flow of coastal water which may 
transport eggs and young from breeding populations located to the north. 


In October, 1971, Ichthyological Associates, Inc. 
began an ecological survey of the New Jersey 
coast from Long Beach Island to Brigantine 
Island. Since March, 1972, invertebrates were 
systematically collected by a variey of methods 
including substrate panels, clam dredge, ponar 
grab, lobster pots, trawl, and SCUBA gear as 
reported by Carlo, Hondo, and Miller (1975) and 

McCullough (1975). 

Recent reports by Franz (1968a, 1970) and 
Loveland, Hendler, and Newkirk (1969) recorded 
nudibranchs from Shark River, Delaware Bay, 
Manasquan River, and Bamegat Bay. Loveland et 
al. (1969) provided a checklist which summarized 
distributional records of nudibranchs from New 
Jersey. Franz (1968b), Marcus (1958), Miner 
(1950) and Pruvot-Fol (1954) discussed their tax- 
onomy and distribution. 


January 27, 1977 

Vol. 91(1) 










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Vol. 91 (1) 

January 27, 1977 



More than 325 macroinvertebrate taxa were 
collected from the study area during the period 
between 1971 and 1975. Opisthobranchs were 
taken between Little Sheepshead Creek and 15 
kilometers southeast of Little Egg Inlet (Fig. 1). 
Nine species of opisthobranchs (represented by 
1,082 specimens) are discussed below (Table 1). 
Specimens are deposited in the collections of 
Absecon Laboratory of Ichthyological Associates, 

Some 95% of the specimens collected were 
taken from artificial structures which included 
lobster pots, substrate panels, buoy lines, ship 
wrecks, and a weather tower. The rest were col- 
lected from natural substrates such as shell rub- 
ble encrusted with bryozoans and drifting 

Pleurobranchaea tarda (Verrill 1880) 

Thirteen specimens were collected by trawl 
during August, October, and November, 1975, ap- 
proximately 15 kilometers southeast of Little Egg 
Inlet. Specimens were taken at depths of 18 to 20 
m. Bottom water temperature at the time of col- 
lection ranged from 14.2° to 17.0° C and salinity 
was 32.0 ppt. 

Abbott (1974) reported specimens off 
Massachusetts and Delaware at depths from 51 to 
567 m. Moore (1964) noted specimens from 
floating Saiyassum in Vineyard Sound, Mass. and 
in dredge samples taken at depths from 60 to 
400 m. Our specimens are the first reported oc- 
currence for New Jersey. 

Acanthodoris pilosa (Miiller 1776) 

Forty-four specimens were collected from 27 
April 1972 through 3 September 1974. They were 
taken in Little Sheepshead Creek, and from Lit- 
tle Egg Inlet to a point 4.8 kilometers southeast 
of Little Egg Inlet at depths of 2 to 11 m. Bottom 
temperatures were 6.5° to 25.0° C and salinities 
were 29.0 to 30.5 ppt. Egg masses were collected 
in June when bottom temperature was 16.0° C 
and salinity was 29.0 ppt. 

Acanthodoris pilosa was found on shell rubble 
which was covered with encrusting bryozoans 
(particularly Alcyonidium sp.) and on cement 
and masonite substrate panels colonized by Al- 


l/J NEW 



Bexh Haven Inlel 


FIG. 1. Area sampled in the vicinity of Little Egg Inlet, 
New Jersey. 

cyonidium, Obelia Jlabellata, and Tubularia 
crocea; 7 were found on the gamma stage 
of Cliona sp. The color of A pilosa varied from 
gray to gray-pink to yellow and blended with the 

Abbott (1974) reported that it was found from 
the Arctic to Ocean City, Maryland and in the 
north Pacific, Japan, and Europe. A specimen 
found in Delaware Bay, New Jersey, was 
reported by Loveland et al. (1969). Acanthodoris 
pilosa is established in natural and man-made 
habitats near Little Egg Inlet but is uncommon. 

Onchidoris bilamellata (Linnaeus 1767) 
(Lamellidoris fusca in Abbott 1974, On- 
chidoris fusca in Moore 1964) 
Eight specimens were collected on a lobster pot 
set from 23 July to 14 August 1973 near a wreck 
located approximately 6.4 kilometers southeast of 
Little Egg Inlet. They were relatively small (total 
length ranged from 5.7 to 6.9 mm; mean 6.3 mm). 
The depth ranged from 14 to 16 m; the bottom 
temperature was 12.5° C, and salinity was 30.5 

Abbott (1974) reported its range in the Atlan- 
tic from the Arctic to Massachusetts and Europe. 


January 27, 1977 

Vol. 91(1) 

These are the first specimens reported from south 
of Ijong Island, New York (Rozsa 1974). 

Dendronotus frondosus (Ascanius 1774) 

One specimen (1.8 mm total length) was col- 
lected on a masonite panel which was set from 23 
April to 1 July 1974. The panel was placed ap- 
proximately 5 m below mean low water on a 
weather tower located 3.7 kilometers southeast of 
Little Egg Inlet. The bottom temperature was 
20.0° C and the salinity was 29.5 ppt. Den- 
dnmotus was associated with the hydroids Obelia 
flahellata and Tubularia crocea. 

Abbott (1974) reported its range in the 
Atlantic is from the Arctic to New Jersey and 
Europe. Loveland et al. (1969) found hundreds of 
specimens associated with Tubularia on a floating 
wharf in Shark River, N. J. 

Tergipes was reported previously from the Arc- 
tic to New Jersey and Europe and Brazil (Abbott 
1974). Loveland et al. (1969) stated it was rare in 
New Jersey; the two previous records were from 
the Shark River. 

Facelina bostoniensis (Couthouy 1838) 

Three specimens were collected between 29 
August 1972 and 8 October 1973 from lobster pots 
and a buoy line located between 3.2 and 4.0 
kilometers southeast of Little Egg Inlet in depths 
of 9 to 10 m. Bottom temperatures were 19.0° to 
22.0° C and salinities were 29.0 to 29.5 ppt. 

Abbott (1974) gave its range as Nova Scotia to 
Connecticut. Rozsa (1974) reported specimens 
from Long Island, New York. These are the first 
reported from New Jersey. 

Doto coronata (Gmelin 1791) 

Twenty-nine specimens were collected from 
early May, 1973, to early December, 1974. Small 
specimens and eggs were collected on floating 
hydroids (Sertularidae) in May, 1973, in Little 
Egg Inlet. A few were found associated with 
Obelia flahellata on cement and masonite panels 
placed 3.7 kilometers southeast of Little Egg In- 
let. Bottom temperatures were 6.0° to 20.0° C and 
salinities were 26.0 to 30.5 ppt. 

Abbott (1974) reported it was distributed from 
the Bay of Fundy to New Jersey and Europe. 
Loveland et al. (1969) noted that it was originally 
described from a collection taken in Great Egg 
Harbor. N. J. by Verrill and Smith (1873). They 
rediscovered it in Shark River in 1968. Our find- 
ings indicate it is established but uncommon in 
the coastal waters off New Jersey. 

Tergipes tergripes (Forskal 1775), (Tergipes 
despectus in Moore 1964, and in Franz 1968a) 

Some 815 specimens were collected between 29 
August 1972 and 6 December 1974 from a 
weather tower, buoy lines, and cement and 
masonite substrate panels located between 3.2 
and 4.8 kilometers southeast of Little Egg Inlet. 
Bottom temperatures were 6.0° to 20.0° C and 
salinities were 29.0 to 31.0 ppt. Most specimens 
were found where 0. flxiheUata was abundant and 
T. crocea was common. 

Cratena pilata (Gould 1870) 

Some 164 specimens were collected between 29 
July 1972 and 5 August 1974 on lobster pots, 
buoy lines, and cement panels located 3.2 and 4.8 
kilometers southeast of Little E^g Inlet at depths 
from 8 to 15 m. Bottom temperatures were 13.0° 
to 21.5° C and salinities were 30.0 ppt. Most 
specimens were collected where T. crocea was 

It occurs from Nova Scotia to North Carolina 
(Abbott 1974) and has been reported from 
Barnegat and Delaware bays. New Jersey by 
Franz (1968a). Our findings indicate it is abun- 
dant in the coastal waters off Little Egg Inlet. 

Aeolidia papillosa (Linne 1761) 

Four specimens and several egg masses were 
collected on 11 June 1973 by SCUBA divers on a 
wreck approximately 8.8 kilometers southeast of 
Little Egg Inlet at a depth of 15 m. Metridium 
senile, the prey of A. papilhsa, was abundant on 
the wreck. Bottom water temperature was 10.0° C 
and salinity was 30.5 ppt. 

Its range in the Atlantic is from the Arctic to 
Maryland and Europe (Abbott 1974), and it has 
been reported from the Shark and Manasquan 
rivers, N. J. by Loveland et al. (1969). Our find- 
ings indicate that breeding populations exist in 
some coastal waters off New Jersey. 

Vol. 91(1) 

January 27, 1977 



Of the 9 opisthobranchs collected from the study 
area, 6 are amphi-Atlantic (occur on both sides of 
the Atlantic) and 3 are west-Atlantic endemic. 
Franz (1970) concluded that 37% of the species 
north of Cape Hatteras are west-Atlantic 
endemics and our findings agree. 

Of the amphi-Atlantic species, A. pilosa, D. cor- 
onata. and T. tergipes are boreal and successful 
reproduction cannot occur above 25° C (Franz 
1970). In this study egg masses of D. coronata 
and A. pilosa were collected at 15° C and 16° C, 
respectively. 0. bilamellata, D. frondosus. and A. 
papillosa are boreo-subarctic species and suc- 
cessful reproduction cannot occur at 
temperatures above 15-20° C. In this study egg 
masses of ^. papillosa were found at 10° C. 

Three factors contribute to successful establish- 
ment of northern nudibranchs in New Jersey. 
Temperature regimes near shore and in Little 
Egg Inlet favor boreal species. Bottom 
temperature never exceeded 25° C between 
March, 1972, and December, 1974. At depths 
greater than 15 m bottom temperature never ex- 
ceeded 21° C, however, during the summer it was 
between 20 and 21° C about 12% of the time. One 
boreo-subarctic species was found reproducing 
below the summer thermocline and this is a 
suitable area for other boreo-subarctic species to 

Loveland et al. (1969) stated that nudibranchs 
and their eggs may be transported southward and 
become rapidly established on man-made struc- 
tures in New Jersey. Some 95% of those collected 
in this study were from submerged man-made 

In summer, 1973, small specimens of 0. 
bilamellata and D. frondosa were collected on 
recently deployed substrates; this suggests they 
were transported by water currents. 
Charlesworth (1968) redrew maps from Bumpus 
(1965) which show the general southwest drift in 
the Middle Atlantic Bight. E. G. & G., En- 
vironmental Consultants (1974) found that the 
prevailing current in the study area in summer, 
1973 was southwest with an average velocity of 
12.1 km/day (surface) and 4.3 km/day (bottom). 
D. frondosa could drift from existing populations 

in Shark River to Little Egg Inlet in less than 2 
weeks. The southwest drift may transport eggs 
and young from northern populations and the 
availability of suitable habitats and thermal 
regimes in the study area facilitate their sur- 


This work is part of an ecological study for the 
proposed offshore Atlantic Generating Station 
sponsored by Public Service Electric and Gas 
Company of New Jersey. Martha M. McCul- 
lough, Jeffrey J. Hondo, and Charles B. Milstein 
collected many of the specimens. Dr. David R. 
Franz, Brooklyn College, confirmed the identifica- 
tion of Acanthodoris pilosa and Lamellidoris 
fiisca and Dr. Larry G. Harris, University of New 
Hampshire, verified the identification of Facelina 

I thank Dr. David R. Franz and Dr. Edward C. 
Raney for reviewing the manuscript, Felicia A. 
Swiecicki for the figure, and Linda N. Dill for 


Abbott, R. T. 1974. American Seashells, the marine moUusca 
of the Atlantic and Pacific coasts of North America. Second 
ed.. Van Nostrand Reinhold Co., New York, N. Y. 663 p. 

Charlesworth, L. J. 1968. Bay, inlet and nearshore marine 
sedimentations: Beach Haven— Little Egg Inlet region, New 
Jersey, Doctoral Thesis. Pts. 1, 2, and 3, University 
Microfilms. Univ. Michigan, Ann Arbor. 

E. G. & G., Environmental Consultants. 1974. Discussion of 
general circulation in the New York Bight area. p. 6-1 
through 8-1 in Summary of oceanographic observations in 
New Jersey coastal waters near 39° 28' N latitude and 74° 
15' W longitude during the period May 1973 through April 
1974. Waltham, Mass. 

Franz, D. R. 1968a. Occurrence and distribution of New 
Jersey Opisthobranchia. Vie Nautilus 82(1): 7-12. 

Franz, D. R. 1968b. Taxonomy of the eolid nudibranch, 
Cratenapilata (Gould). Ches. Set. 9(4): 264-266. 

Franz, D. R. 1970. Zoogeography of northwest Atlantic 
opisthobranch molluscs. Mar. Biol. 7(2): 171-180. 

Garlo, E. V., J. J. Hondo, and G. J. Miller. 1975. Benthic in- 
vertebrates. 2: 26-64. In Ecological studies in the bays and 
other waterways near Little Egg Inlet and in the ocean in 
the vicinity of the proposed site for the Atlantic Generating 
Station, New Jersey. Ichthyological Assoc, Inc., Ithaca, New 

Loveland. R. E., G. Hendler. G. Newkirk. 1969. New records of 
nudibranchs from New Jersey. Veliger l\{i): 418-420. 

McCullough, M. M. 1975. Epifauna, 2: 13-21. In Ecological 
studies in the bays and other waterways near Little E^g 


January 27, 1977 

Vol. 91(1) 

Inlet and in the ocean in the vicinity of the proposed site 
for the Atlantic Generating Station, New Jersey. 
Ichthyological Assoc.. Inc.. Ithaca. N. Y. 

Marcus. E. 1958. On western Atlantic opisthobranchiate 
gastropods. Amer. Mus. Nointates. No. 1906. 82 p. 

Miner. R. W. 1950. Field Bonk of Seashore Life. G. P. Put- 
nam's Sons. New York, N. Y. 888 p. 

Moore, G. M. 1964. Shell-less Opisthobranchia, p. 1.5.3-164. In 

R I. Smith (ed.) Keys to marine invertebrates of the Woods 

Hole Region. Contr. 11, System.-Ecol. Program. Mar. Biol. 

Lab.. Woods Hole, Mass. 
Pruvot-Fol, A. 1954. MoUusques opisthobranches. Faune de 

France 58: 421-436. 
Rozsa, R. 1974. Preliminary checklist of the nudibranchs and 

sacoglossa of Long Island. New York Shell Oub Notes 200: 



Wiliiam G. Lyons 

Florida Department of Natural Resources 
Marine Research Laboratory' 
St. Petersburg, Florida 33701 


Eupleura sulcidentata is reported from estuarine and coastal sites in southeast 
Florida. Cuba, and tivo Bahamian Islands, demonstrating that the species is not a 
west Florida endemic, and confirming Doll's original record fi-om Cuba. 

In 1972, I collected six freshly dead shells of 
Eupleura (Fig. 1) in beach drift along a sand spit 
at White Sound on the lagoonal side of Elbow 
Cay, Great Abaco, Bahamas. A literature search 
(part of an ongoing treatment of the shallow 
water Bahamian molluscan fauna) failed to 
reveal any Bahamian records of Eupleura, so 
specimens were sent to Dr. Emily Yokes, Tulane 
University, who identified them as E. sulciden- 
tata Dall, 1890. The specimens are deposited in 
the Marine Research Laboratory invertebrate 
reference collection (FSBC I) at St. Petersburg. 

In his original description, Dall defined the 
range of E. sulcidentata as "Gulf coast of Florida, 
shores of Cuba." Smith (1937) also listed Cuba 
within the range of the species, but Dall's Cuban 
citation was evidently considered erroneous by 
Johnson (1934), who listed only the Gulf coast of 
Florida and Florida Keys, and by Abbott (1954, 
1968), who further restricted it to west Florida. 
Lyons et al. (1971) followed the latter in consider- 
ing the species a west Florida endemic. Abbott 
(1974) listed E. sulcidentata at Bimini, Bahamas, 
revising its range to include both the west coast 
of Florida and Bimini. A report of E. sulciden- 

Contribution No. 290. 

tata from Caibarien, on the north central Cuban 
coast (Jaume and Sarasua, 1943) has evidently 
been overlooked by subsequent authors. Dr. Ab- 
bott suggested I contact Mr. J. C. Finlay, who 
allowed me to examine nine Cuban specimens 
(Figs. 2, 3) collected by him during 1957-1958 in 
depths of 3-4 m on the Varadero side of the Bay 
of Cardenas, about 200 km northwest of 
Caibarien. Mr. Dan Steger provided an addi- 
tional specimen from Varadero. Mr. Finlay also 
provided three specimens (Fig. 4) collected off 
Rickenbacker Causeway, Biscayne Bay, Miami, 
Florida, during 1949-50. Most recently, I have ex- 
amined 12 specimens (Fig. 5) collected by Mr. 
Gene Everson while night diving in depths of 5-6 
m immediately off Lake Worth Inlet, north of 
West Palm Beach, Florida. 

Eupleura sulcidentata occurs in estuaries along 
the entire Florida west coast. Tabb and Manning 
(1961) report specimens from Cape Sable and 
northern Florida Bay, Cooley (manuscript) has 
found the species at Pensacola Bay, and others 
have been reported at many points intermediate 
to these localities. The snails are common in 
Tampa Bay (Fig. 6). where they usually live on 
rocks over sand, on oyster reefe, or in grassbeds 
in higher salinity portions of the Bay: they also 

Vol. 91(1) 

January 27, 1977 


FIGS. 1-6. Eupleura sulcidentata DaH: Fig. 1 - Elbow Cay. 
Gt. Ahaco (FSBC I 10131). Pigs. 2, 3 - Cardenas Bay. Cuba 
(Finlay Coll.). Fig. 4 Biscatpte Bay (Finlay Coll.). Fig. 5 — 
Lake Worth Inlet (Everson Coll.). Fig. 6 — Tampa Bay. 
Florida (FSBC 1 2672). All figures X2. 

occur near beaches where conditions remain 
essentially estuarine. Habitat near the beach at 
Elbow Cay included sand and turtle grass, 
(Tlmlassia testudinum Konig) with occasional 
rocks scattered throughout the area. Mr. Finlay 
states that he commonly dredged E. sulcidentata 
in 2-3 m on muddy sand in the Bay of Cardenas. 
At Biscayne Bay, specimens were "not infre- 
quently found clinging to the outside of smooth 
objects such as bottles, cans, etc." Lake Worth In- 
let specimens were found in shell rubble on sand, 
apparently similar to areas where the species oc- 
curs in nearshore waters of west Florida. The 
Bahamian, Cuban, and Biscayne Bay sites are 
relatively estuarine compared to other tropical 
habitats, but faunal assemblages differ con- 
siderably from those where E. sulcidentata occurs 
along west Florida. 

Lake Worth Inlet may approach the northern 
range limit of E sulcidentata on the Florida east 
coast. Extensive collecting by me at St. Lucie In- 

let. 45 km to the north, has not produced this 
species, although its northern congener, E. 
candata (Say, 1822) has been found there. 

Mr. Finlay 's specimens, as well as the report 
by Jaume and Sarasua, confirm Ball's original 
contention that E. sulcidentata is a component of 
the Cuban fauna. Specimens from Lake Worth, 
Biscayne Bay, and two Bahamian localities 
demonstrate that the range of the species is con- 
siderably greater than has been recently 

I thank Messrs. John C. Finlay, Newark, 
Delaware, the late Dan Steger, Tampa, Florida, 
and Gene Everson, Ft. Lauderdale, Florida, for 
graciously loaning specimens, and Mrs. Sally D. 
Kaicher. St. Petersburg, for preparing the figures. 
Dr. R. Tucker Abbott. Greenville. Delaware, pro- 
vided additional information and comment. David 
K. Camp and Mark J. Poff kindly read the 


Abbott, R. T. 1954. American Seashells. D. Van Nostrand Co., 
Inc.. Princeton. 541 p. 

Abbott, R. T. 1968. Seashells of North America. Golden Press, 
New York. 280 p. 

Abbott, R. T. 1974. American Seashells. 2nd ed. Van 
Nostrand- Reinhold Co., New York. 663 p., 24 pis. 

Cooley. N. R. (Manuscript). An inventory of the estuarine 
fauna in the vicinity of Pensacola, Florida. 

Dall. W. H. 1890. Contributions to the Tertiary fauna of 
Florida, with especial reference to the Miocene silex-beds of 
Tampa and the Pliocene beds of the Caloosahatchie River. 
Part I. Pulmonate. opisthobranchiate and orthodont 
gastropods. Trans. Wagner Free Inst. Sci. Phila.. 3: 200 p. 

Jaume. M. L. and H. Sarasua. 1943. Notas sobre moluscos 
marinos cubanos. Rev. Soc. Mai. "Carlos de la Torre" 1(2): 
52-61, 1 pi. 

Johnson, C. W. 1934 List of marine mollusca of the Atlantic 
coast from Labrador to Texas. Proc. Boston Soc. Nat. Hist., 
40(1): 204 p. 

Lyons, W. G., S. P. Cobb. D. K. Camp. J. A. Mountain, T. 
Savage. L. Lyons, and E. A. Joyce, Jr. 1971. Preliminary in- 
ventory of marine invertebrates collected near the electrical 
generating plant. Crystal River, Florida, in 1969. Fla Dep. 
Nat. Resour. Mar. Res. Lab.. Prof. Pap. Ser., 14: 45 p. 

Smith, M. 1937. East coast marine shells. Edwards Brothers, 
Inc., Ann Arbor. 308 p. 

Tabb. D. C, and R. B. Manning. 1961. A checklist of the flora 
and fauna of northern Florida Bay and adjacent brackish 
waters of the Florida mainland collected during the period 
July 1957 through September 1960. Bull. Mar Set. Gulf 
Carib.. ll(4):552-649. 


January 27, 1977 

Vol. 91 (1) 


Henk K. Mienis 

Department of Zoology 

Hebrew University 

Jerusalem , Israel 


snails: Gastrocopta procera (Gould). Hawaiia 

Three North American land 
minuscula (Binney) and Zonitoides arboreus (Say) are reported fi-om Israel. 

Recent investigations have revealed the 
presence of several North American land snails 
in Israel. Preliminary information is given in 
this report in the hope that more attention will 
be paid to other cases of introduced land 
mollusks in the Middle East. 

The material on which this work is based was 
collected during field work carried out by the 
author in support of the land snail project of the 
"Fauna Palaestina Committee". 

The following North American land mollusks 
were collected in Israel: 

Gastrocopta (Gastrocopta) procera (Gould, 1840) 

In December 1972 a few empty shells of this 
species were collected by Mr. S. Davis during a 
field trip of students of the Hebrew University of 
Jerusalem to the oasis of 'En Gedi, on the 
western shore of the Dead Sea. About one week 
later, very large numbers of this minute species 
were found in litter under palm trees in the ir- 
rigated palm gardens bordering the fields of kib- 
butz 'En Gedi by Prof. G. Haas, Mr. S. Davis, 
Miss T. Felsenburg and the author. More than 
ten thousand specimens were extracted from less 
than four kilograms of litter. 

It was first identified as Gastrocopta procera 
mcclungi (Hanna & Johnston, 1913) by Dr. L. 
Forcart, but according to Mr. L. R. Hubricht (per. 
comm.) all the specimens belong to the nominate 
species Gastrocopta procera ((Jould). According to 
the latter, it is almost impossible to discriminate 
properly any subspecies within the species G. pi-o- 
cera because of the many intermediate forms. 

Hawaiia minuscula (Binney, 1840) 
Like Gastrocopta procera this species was 

found in large numbers in a litter sample taken 
in the irrigated palm gardens of kibbutz 'En 
Gedi. The identification of this species based on 
shell characters was confirmed by Dr. L. Forcart. 
Dr. A. Riedel later found the anatomy of a living 
specimen to agree in every detail with that of 
typical//, minuscula. 

Zonitoides (Zonitellus) arboreus (Say, 1816) 

Very large colonies of this species are present 
in the open tree nursery of kibbutz Netzer 
Sereni. Snails were first observed by the author 
in January 1970, but this species must have 
already been well established as thousands of liv- 
ing snails were present. The snails are living on 
and underneath containers (mainly tin cans) in 
which saplings of sub-tropical fruit trees are 
cultivated, in densities reaching 25 per container. 
Eggs and juveniles are found during the entire 
year, but are most numerous in the spring 
(March-May). With the sale of young trees, snails 
are transported to orchards and other nurseries. 

The identification of Z. arboreus from kibbutz 
Netzer Sereni has been confirmed by Dr. L. For- 
cart and Dr. C. 0. van Regteren Altena. 

Recently additional specimens of Z. arboreus 
were collected by the author in an open 
greenhouse of the Old Botanical Garden of the 
Tel Aviv University near Abu Kabir, Tel Aviv (8 
January 1975). A single specimen was found in a 
hothouse of the Botanical Garden at the Givat 
Ram campus of the Hebrew University of Jerusa- 
lem (5 June 1975). 


Zonitoides arboreus is a well known 
greenhouse species which is widely distributed 

Vol. 91(1) 

January 27, 1977 


over the whole world. (Pilsbry, 1946). It may have 
been introduced with plants imported from North 
America or from hothouses in Europe. 

In the cases of Gastrocopta procera and 
H(uraiia miymsmla. there is a clear indication 
that they were imported directly from Southern 
California. Both species were found in litter 
under palm trees which were directly imported 
from a nursery in the Coachello Valley in the 
Salton Lake area. According to Pilsbry (1948) this 
species was not known to live outside America. 

From the large numbers in which these three 
species have been collected, it is clear that all 
have adapted very well under the artificial condi- 
tions in Israel. Further passive dispersal of 
Zonitoides arboreus is currently going on. 
However, there is no positive data available 
regarding the presence of this species in other 

nurseries or orchards in Israel. Further dispersal 
of Gastrocopta procera or Hawaiia minuscula 
seems very unlikely, as both are living in the 
isolated oasis of 'En Gedi in the Judean Desert, 
and there only in irrigated palm gardens. 


Tlie author wishes to express his gratitude to 
Dr. L. Forcart (Basel), Dr. C. C. van Regteren 
Altena (Leiden), Dr. A. Riedel (Warszawa) and 
Mr. L. R. Hubricht (Meridian) for their help in 
the identification of the discussed material. 


Pilsbr>', H. A. 1946. Land MoUusca of North America (North 
of Me.xico). Acad. Nat. Sci. Philadelphia, Monog. 3. 2(1): 481. 

Pilsbry. H. A. 1948. Land Mollusca of North America (North 
of Me.xico). Acad. Nat. Sci. Philadelphia, Monog. .3, 2(2): 


S. K. Raut and K. C. Ghose 

Department of Zoology 

University of Calcutta 

35 B.C. Road, Calcutta - 70(X)19 INDIA. 

Water conservation is a serious problem in 
land snails. Aestivation is the normal mechanism 
to tide over the adverse conditions during dry 
seasons in temperate and tropical countries. 

Studies on the orientation of the shell aperture 
in hibernating snails are very few. An upwardly 
directed aperture during hibernation is common 
in many land snails (Binney, 1851), in Mesodon 
thifroidu,^ and Allogona profunda (Blinn, 1963), 
and commonly upward in A. ptychophora 
(Carney, 1967). A pronounced effect is expected in 
specimens with long periods of aestivation, which 
is supported from the studies on Achatinafulica. 


Three cages measuring 600 x 450 cm and 240 
cm high were erected in a shady place in the 

campus of Calcutta University at Ballygunge. 
Sized wood, 7.5 x 5 cm thick, and of appropriate 
length were used. The posts were fixed in the soil 
with concrete bases. The sides and the ceiling 
were covered with 1-cm expanded metal net. The 
soil of the floor of the cages was loosened with 

A limited amount of water was sprayed on the 
soil on October 13 and 14, 1974. Then 200 healthy, 
active, juvenile and adult Achatina collected from 
their natural habitat were released in each of the 
cages No. 1 and 2. The snails were acclimatized for 
18 days and water was regularly sprayed during 
the period to keep the soil sufficiently moist and 
maintain a high percentage of humidity in the 
cages. Favourite food was supplied in excess and 
strict hygienic conditions were maintained. The 


January 27. 1!)77 

Vol. 91(1) 

snails were vigorously active in the period of ac- 

To simulate the natural habitat of Achatina. 
water-spraying was stopped on 2nd November, 
but the food supply was continued. 


Nov. 7, 1974: Most of the snails in both the 
cages were partially buried in the soil or moving 
to a corner indicating preparation for aestivation. 
Some of the snails started moving up the frame 
of the cage but they were brought down and 
released on the soil. 

Nov. 11, 1974: The rest of the snails became in- 

Nov. 13, 1974: Epiphragm was formed in all 
specimens. In all cases the shell aperture was 
directed downward. 

Nov. 17, 1974: The aestivating snails in cage 
No. 1 were turned upside down, i.e., the aperture 
was directed upwards. The snails of the cage No. 
2 were left undisturbed. 

There was no rainfall until February, 1975, 
when there occurred a total rainfall of 10.2 mm 
in 5 days at certain intervals. Feb. 11, 1975: rain- 
fall 3.9 mm. Feb. 12, 1975: rainfall 3.2 mm. 

The humidity in February was maximum 95%, 
minimum 35%. Temperature mean maximum 27°, 
mean minimum 15.5°. 

Feb. 12, 1975: 173 snails became active in cage 
No. 1. The remaining were already dead. Four 
specimens pushed out the epiphragm but soon 
died. 114 snails became active in cage No. 2. Ten 
snails were found dead under the epiphragm. 

In a few days the snails in both the cages 
underwent aestivation, all with the aperture 
downward. The snails of cage No. 1 were again 
turned upside down, so that the aperture faced 

The month of March was dry. In the following 
month the total rainfall was 5.1 mm in 4 days. 
Apr. 25, 1975: Rainfall 3.2 mm; Apr. 26, 1975: 
Rainfall 1.6 mm. The humidity in April was ma.x- 
imum 91% and minimum 19%. Temperature 
mean maximum 35.4°, mean minimum 24.8°. 

Apr. 26, 1975: 107 snails became active in cage 
No. 1. They were immediately transferred to cage 
No. 3. 76 snails were active in cage No. 2. Apr. 
27, 1975: 55 snails were dead under the 

epiphragm. the foot and head of 11 snails were 
pushed out of the shell and died in that state in 
cage No. 1, and dead snails counted were 26 in 
cage No. 2. 

The snails in cages 3 and 2 aestivated within a 
few days with the aperture downward. The snails 
of cage No. 3 were again turned upside down. 

A weak monsoon appeared in the first week of 
June and with heavy showers in the middle of 
the month all live snails in the cages became ac- 
tive. The number dead was 44 in cage No. 3 and 
.56 in cage No. 2. 


The aestivation period in Stylommatophora dif- 
fers with species and the country where they live. 
For Achatina, the period is long between the 
rains in Mauritius and Ceylon (Green, 1910: Hut- 
son, 1920); during the dry spell in Singapore 
(South, 1926); November to March in Hong Kong 
(Herklots, 1948); November to June in India 
(Ghose, 1959) and February to March in Hawaii 
(Kondo, 1964). Helicella virgata aestivate for 
about 5 months in Australia (Pomeroy, 1968), 
while the period is only 2 months during summer 
for Macrochlamys glaum in India (Hora, 1928). 
Aiiophnnta is reported to aestivate in summer in 
India (Hora and Rao, 1928) but the duration is 
not on record. 

Observations on the orientation of shell aper- 
ture during hibernation in cold countries are on 
record (Binney, 1851; Blinn. 1963; Carney, 1967). 
The sole information on the influence of orienta- 
tion of shell aperture during aestivation in 
Allogona ptychophora is that of Carney (1966) in 
Montana, U.S.A., where the snails are covered 
with snow for sometime. 

The main function of epiphragm appears to be 
conservation of water. Both permeable and non- 
permeable epiphragms have been reported in dif- 
ferent Stylommatophora. The epiphragm is per- 
forated in Helix aspersa (Allman, 1894-95), but 
Smith (1899) recorded no perforation in the 
epiphragm of H. aspersa and H. pomatia. Rees 
(1964) considers the epiphragm of H. pomatia as 
slightly permeable. Perforations on the 
epiphragm have been reported from Thau mast us 
sangoae (Smith, 1904), Gessula hastula and 
Zootecus insularis (Hora, 1928) but these are 

Vol. 91(1) 

January 27, 1977 


lacking in M glauca (Hora 1928). The epiphragm 
of Achatina is not permeable and a narrow slit- 
like opening in the epiphragm against the 
pneumostome maintains communication between 
the lung and the atmosphere. Smith (1899), 
however, states that the slitlike structure in A. 
immaailata is closed. 

Loss of water, though in small amounts, is 
associated with a reduced rate of respiration dur- 
ing aestivation. It appears that to minimize the 
loss further the shell aperture in A. fidica is 
placed against the substratum, be it soil or some 
other substance. The air locked in between the 
epiphragm and the soil is considerably cooler 
than the surrounding air. After two months 
of aestivation and a week after a shower, con- 
siderable amount of moisture in the expired air 
condenses into small drops of water on the 
epiphragm. In specimens with upturned apertures 
such phenomenon was totally absent. 

In Allogona ptychoph<yra the mortality rate is 
normally 15.8%, but in specimens turned upside 
down it is 36% (Carney, 1966). In Achatina. the 
normal mortality percentage was 46 but in- 
creased to 68.5 in the upside down group. 

It appears that the method of aestivation with 
the aperture of Achatina placed against the soil 
is an adaptation towards conservation of water to 
the highest possible degree. 


Allman. G. J. 1894-95. Note on the Formation of the 

Epiphragm of Helix futpersa. Pruc. Linn. Soc. Land. 25: 

Binney. A. 1851. The terrestrial air-lnvathing moltusks of the 

United States and adjarent territories of North America. 

Vol. 4. Little & Brown. Boston. 
BHnn, W. 1963. Exrology of the land snails, Mcsodon thifroidtts 

and Allogona profunda. EkoUiyyM: 498-505. 
Carney, W. P. 1966. MortaUty and apertural orientation in 

Allogona ptychophora during winter hibernation in Mon- 
tana. The Naiddus 79(4): 1.34-36. 
Ghose. K. C. 1959. Observations on the mating and oviposition 

of two land pulmonates, Achatina fidica Bowdich and 

Macrochlamys indica Godwin-Austein. J. Bombay Nat. Hist. 

Soc. 56(2): 183-87. 
Green, E. N. 1910. African snail {Achatina fidica). Trap. 

Agriculturist 35(4): 311. 
Herklots, G. A. C. 1948. Giant African snail Achatina fulica 

Fer. Food and Flowers 1(1): 1-4. 
Hora, S. L. 1928. Hibernation and aestivation in gastropod 

molluscs: on the habits of a slug from Dalhousie (Western 

Himalayas), with remarks on certain other species of 

gastropod molluscs. Rec Ind. Mus. 30: 3.57-73. 
Hora, S. L. and Rao. H. S. 1927. Hibernation and aestivation 

in gastropod molluscs. Rec. Ind. Mus. 29(2): 49-62. 
Hutson. J. C. 1920. The African snail (Achatina fulica). Trap. 

Agricidturist 55: 217-25. 
Kondo, Y. 1964. Growth rates in Achatina fidica. The 

Pomeroy, D. E. 1968. Dormancy in the land snails. Helicella 

virgata (Pulmonata). Aust. J. Zool. 16: 857-69. 
Rees. W. J. 1964. A review of breathing devices in land oper- 

culate snails. Proc. Malac. Soc. Land. 36: .55-67. 
Smith, E. A. 1899. Notes on the Epiphragm of Achatina im- 

maculata Lam. Pirx-. Malac. Soc. Land. 3: 309-310. 
Smith, E. A. 1904. Notes on the Epiphragms of Thaumastus 

sangoae and T. tntaeniatus. Proc. Malac. Soc. Lond. 6: 3-4. 


Shell Club will host the A.M.U. during its 42nd 
Annual Meeting July 11-15,1977. There will be a 
symposium on the Evolution of Mollusca, as well 
as regular papers. Contact President George M. 
Davis, Academy of Natural Sciences of Philadel- 
phia, 19th and the Parkway, Philadelphia, Pa. 
19103. Accommodations will be in the spacious 
Naples Beach Club Hotel ($19 single; $22 double). 
Contact Jerome M. Bijur, 135 Seventh Avenue 
North, Naples, Fl. 33940. Detail notices are being 
mailed to A.M.U. members. 


January 27. 1977 

Vol. 91 (1) 


Ralph W. Taylor and Clement L. Counts. Ill 

Department of Biological Sciences 

Marshall University 
Huntington. West Virginia 25701 

In the growing mass of literature concerning 
the Asiatic clam, Corhieula manilensis (Philippi), 
few references have been made to their use as a 
food item by other organisms. Lowery (1974) 
noted in his mammal survey of Louisiana that 
the northern raccoon, Procyon lot(yr (L.) utilizes 
many molluscs in its diet. Many small streams in 
West Virginia attest to this habit as sand bars in 
these streams are often littered with many 
broken, empty shells of bivalves surrounded by 
footprints and scats of P. lotor. The present note 
reports the use of C. manilerms as a component 
in the diet of F. lotor in West Virginia. 

Shells of C. manilensis were found in great 
numbers along the southern bank of the Ohio 
River, adjacent to a marsh, 2 miles north of 

Lesage, Cabell County. West Virginia, in 
September 1976. Many of the shells were broken 
and found in scattered heaps. Surrounding the 
shells were the footprints and scats of P. lotor. 
Analysis of the scats revealed the presence of 
shell fragments and one intact valve of a young 
C. trianilensis, as well as assorted varieties of 

Voucher specimens have been placed at the 
Delaware Museum of Natural History (DMNH 


Lowery. G. H., .Jr. 1974. The Mammals of Louisiana and Its 
Adjacent Waters. Louisiana State Univ. Press (Baton 
Rouge). xxiii:.565pp. 


Carl M. Thompson and Richard E. Sparks 

Illinois Natural History Survey 
Havana. Illinois 62644 


In 197i-75, specimens of the Asiatic Clam, Corbicula manilensis. were col- 
lected at six locations on the Illinois River. Aye determinations of clams col- 
lected suggest that Corbknla first appeared in the Illinois River in 1970-71. 

Recent collections of the introduced Asiatic 
clam, Corbicula manilensis, at six locations on 
the Illinois River indicate a rapid range exten- 
sion into this river system. On 23 August 1974, 
we found 3 non-living shells of Corbicula on the 
gravel shore of the Illinois River just downstream 

from the ferry landing at Kampsville, Calhoun 
County, Illinois (Illinois River mile 32.0).' The 
.second find was made on 18 September 1974 at 

' River miles above the confluence with the Mississippi River 
as recorded in Charts of the Illinois Waterway. 1970, U. S. 
Army Corps of Engineers. 

Vol. 91(1) 

January 27, 1977 


Turkey Island Chute, Illinois River above 
Kingston Mines, Fulton County, Illinois (River 
mile 148.3). As before, the specimens were col- 
lected on shore— this time in a concentration of 
dead and weathered mollusk shells. In all, 12 in- 
dividuals were collected at Turkey Island, 6 of 
which contained tissue. Three specimens were 
tightly closed and were found at water's edge, 
suggesting recent desiccation. On 28 October 1974, 
a third collection of 6 dead shells was made at 
the lower end of Bath Chute, Illinois River below 
Bath, Mason County, Illinois (River mile 106.7). 
Once again, all specimens were found on shore in 
a deposit of dead mussel shells. Clam collections 
were made after a rapid July-August drop in 
pool water levels of 18 feet at Bath and Kingston 
Mines and 8 feet at Kampsville. Prior to this, the 
nearest previous locality record was for the 
Mississippi River at Granite City, Madison Coun- 
ty, Illinois— first appearing there in 1965 
(Thomerson and Myer, 1970). Three new records 
were made in 1975: four specimens were found 
on-shore at Upper Bath Chute (Illinois River mile 
113.5) on 20 August, 1975. They ranged in shell 
length from 10 to 14 mm, indicating they were 
two-year-old clams. One live individual was col- 
lected with an Eckman dredge from Sugar Creek 
Island Chute (Illinois River mile 95.0) on 3 
September, 1975. Shell length was 8 mm, also a 
clam of the second-year-class. One other live 
specimen was collected by Eckman dredging at 
Sugar Island Chute (Illinois River mile 260.5) on 
25 September, 1975. It was 12 mm long, a two- 
year-old individual. 

Other knovm Illinois records include the entire 
length of the Ohio River bordering Illinois; at 
two localities on the Wabash River— below New 
Haven, Gallatin County and below Rising Sun, 
White County (Parmalee, 1965); Granite City, 
Madison County (Thomerson and Myer, 1970); the 
Kaskaskia River near Baldwin, Randolph County, 
25 miles above the confluence with the Mississip- 
pi^ Crab Orchard Lake, Williamson County'; 
and at Lake Sangchris, a 2700-acre Com- 

' Personal communication, Mr. Donald W. Dufford. Aquatic 
Biologist. Illinois Natural Historj- Survey. 
' Personal communication, Dr. R. Weldon Larimore, Aquatic 
Biologist. Illinois Natural History Survey. 

monwealth Edison power company impoundment 
near Springfield, Sangamon County'. At this lat- 
ter site, Corbicula has impeded water flow in the 
plant cooling system. 

National distribution records have been com- 
piled by Sinclair (1971). A recent discovery near 
Lansing, Iowa (Eckblad, 1975) establishes the 
northernmost extent of Corbicula in the 
Mississippi River System and the Midwest. It is 
noteworthy that Corbicula at Lansing occurs in 
heated effluent from a power plant. Also, the Il- 
linois River in the vicinity of our collection sites 
is warmer than the Mississippi at approximately 
the same latitude. In 1973 during the period 1 
November to 28 February, there were 103 days 
when the water temperatures were measured on 
the same days on both the Mississippi River at 
Alton, Illinois and 75 miles north on the Illinois 
River at LaGrange (River mile 80.2) (USGS, 
1973). Even though the Illinois River location was 
farther north than the Mississippi River station, 
there were only 19 days when the minimum daily 
temperature was at the freezing point on the Il- 
linois and 36 days at the freezing point on the 
Mississippi. The yearly mean temperature on the 
Illinois at Havana (River mile 119.6) was 55° F. 
while the Mississippi at Keokuk, Iowa, at approx- 
imately the same latitude was 49° F. (Illinois 
EPA, 1972). The thermal tolerance and preference 
of Corbicula need to be determined before any 
definitive statements can be made about the 
probable northern limits of its range extension. 

Identification of Corbicula manilensis was 
made by descriptive characters given by Sinclair 
and Isom (1963) and Burch (1972). Shell length 
measurements were made on all specimens and 
compared with published grovvth values (Sinclair 
and Isom, 1961) for approximate age determina- 
tion. All three valves found at the Kampsville 
location were 12 mm in length indicating they 
were clams of the second "year-class". Of the 
specimens taken at Turkey Island seven ranged 
from 12-18 mm and five ranged from 20-26 mm, 
two- and three-year-old clams. Valve lengths for 
the Bath Chute collection ranged from 17-29 mm, 
also two- and three-year-old specimens, with the 
largest individual, 29 mm, possibly representing 
the fourth year-class. If the clams collected in the 


January 27, 1977 

Vol. 91(1) 

Illinois River are considered tx) be representative, 
Corhk'ula first occurred in the river in 1970-1971. 


Burch. J. B.. 1972. Freshwater Sphaeriacean clams (MoUusca: 
Pelec>'peda) of North America. Biota of Freshwater Eco- 
systems Identification Manual No. 3. U. S. Elivironmental 
Protection Agency. .'11 p. 

hxkbiad, .James N.. 197.5. The Asian clam Corbiaila in the up- 
per Mississippi River. The Nautiltis 89(1): 4. 

Illinois Environmental Protection Agency, 1972. Water quali- 
ty network. 1972 summary of data. Vol. 2. Illinois, Fox. 
Sangamon, and Kankakee Basins. 243 p. Vol. 4. Mississippi 
River (South. South Central, Central, North Central, 
North), Big Muddy River. Kaskaskia River, and Rock River 
Basin, 538 pp. Springfield. Illinois. 

Ingram. William M., 19.59. Asiatic clams as potential pests in 
California Water Supplies. Journal American Water WwA".s 
Association 51(3): 3a3-370. 

Ingram. William M.. L. Keup, and C. Henderson, 1964. Asiatic 
Clams at Parker, Arizona. The Nautilus 11 (i): 121-124. 

Parmalee. Paul W.. 1965. Asiatic clam (Gwbicula) in Illinois. 

Transactions of the Illinois State Academy of Science 58(1): 

Sinclair. Ralph M. and Billy G. Isom. 1961. A preliminary 
report on the introduced Asiatic clam Corbicula in Ten- 
nessee. Tennessee Department of Public Health. Tennessee 
Stream Pollution Control Board. 33 pp. 

Sinclair. Ralph M. IWi!. Effects of an introduced clam (Cor- 
bicula) on water quality in the Tennessee River Valley. 
Proceedings of the Second Industrial Waste Conference, 
Vanderbilt University. Tennessee Department of Public 
Health Tennessee Stream Pollution Control Board. 14 pp. 

Sinclair, Ralph M. and B.C. Isom, 1963. Further studies on the 
introduced Asiatic Clam (Corbicula) in Tennessee. Ten- 
nessee Department of Public Health. Tennessee Stream 
Pollution Control Board. 75 pp. 

Sinclair, Ralph M., 1971. Annotated bibliography on the exotic 
bi-valve Corbicula in North America, 1900-1971. Sterkiana 
43: 11-18. 

Thomerson. Jamie E. and Donal G. Myer. 1970. Corbicula 
manilensi.'i: range extension upstream in the Mississippi 

United States Geological Survey. 1973. Water resources data 
for Illinois. District Chief. Water Resources Division. U. S. 
(jeological Survey. Champaign. Illinois. 300 pp. 


Pseudothecosomata, Gymnosomata attd 
Heteropoda (Gastropoda). By S. van der Spoel. 
1976. 484 pp., 246 figs. Bohn, Scheltema and 
Holkema, Utrecht. Hardbacii, $60.00 U.S. 

This book serves to bring together most of the 
current information on the pelagic pteropods and 
heteropods. A large mass of data, identification 
keys and drawings, and distributional maps will 
assist oceanographers working on plankton. The 
bibliography is extensive. The book, however, is 
difficult to use. 

The several indices are tucked away in various 
places in the text, and upon finding a reference 
the reader is led, not to a page number, but to a 
species number located on pages 16-22. Finally at 
this point the figures, maps and page numbers 
are revealed. The main treatment of a species 
does not give any geographical information, nor a 
reference to the proper maps at the end of the 
book. One must search first among the systematic 
table of contents to find a reference to the maps. 


The nomenclatorial treatment of the 
heteropods is very unsatisfactory, with a few 
names being entirely ignored, such as Atlanta in- 
flata Orbigny, 1836. The Atlanta names 
legitimately proposed by Orbigny in 1836, Man- 
dralisca in 1840 and J. E. Gray in 1850 are 
erroneously considered to be nomina nuda 
(tesselata [sic] Gould, 1852 and pulchella Verrill, 
1884), presumably in an attempt to conserve cer- 
tain better-known names. However, Gray's 1850 
Cavolinia names are accepted. The genus 
Mirrodonta Bonnevie, used by van der Spoel. is 
three times a homonym, and should be replaced 
by Prionoglossa Tesch, 1950. 

Some additional illustrations of recently 
described, shelled pteropods and newly recognized 
forma are included with convenient keys. The 
new subfamily Glebinae is proposed in the Cym- 

R. Tucker Abbott 
Delaware Museum of Nation History 

Vol. 91(1) 

January 27, 1977 


Portrait o/All-j/n G. Smith taken in 1955 
by Moulin Studios of San Francisco. 



With the passing of Allyn G. Smith on August 
18th, 1976, malacology lost one of its most ad- 
mired and knowledgeable students of West 
American mollusks. Bom June 4, 1893, in Hart- 
ford, Connecticut, Allyn went to California in 
1908, and later attended the University of 
California at Berkeley, receiving a B. S. in Elec- 
trical Engineering in 1916. After serving in the 
U. S. Army in World War I, he returned to his 

Alma Mater, to chair the Technical Department 
in the Extension Division (1920-1924). In 1925, he 
joined the Pacific Telephone and Telegraph Co., 
where he held the title of Supervisor of Personnel 
at the time of his retirement in 19.55. 

His special interests in pulmonate gastropods 
and the chitons was initially generated by his 
close friend, S. Stillman Berry, who fondly refers 
to him as "one of my boys". He also knew the 
Californian malacologist, Jo.siah Keep. During his 
business career Allyn devoted much of his spare 
time to field work, and he contributed numerous 
malacological articles to journals. A major con- 
tribution was a survey of "The Marine Mollusks 
and Brachiopods of Monterey Bay, California and 
Vicinity" (with Mackenzie Gordon, Jr.) published 
in 1948. 

Upon his retirement, he had hoped to devote 
full time to research, but his administrative 
talents were drafted by the California Academy 
of Sciences, where he had served as a Research 
Associate in Malacology since 1939. There he 
started a new career in the capacity of Executive 
Assistant to the director, 1955-1960, and as 
Chairman and Associate Curator, he later 
revitalized the Department of Invertebrate 
Zoology, 1960-72. Despite these duties, he 
prepared the section on "Amphineura" for the 
Treatise on Invertebrate Paleontology, 1960, and 
he continued publishing and field work, including 
participation in the Galapagos International 
Science Project in 1964. Author of 104 papers, 
two of which appeared in 1976, he was active 
until shortly before his death. 

An energetic and compassionate man of many 
interests and achievements, Allyn will be sorely 
missed by his many friends and colleagues. He 
leaves his wife, Katharine, and three children. 

William K. Emerson, Curator of Mollusks 

The American Museum of Natural History 

New York, New York 

Murex Shells of 
the World 

An Illustrated Guide to the Muricidae. 
George E. Radtvin & Anthony D'Attilio. Photos 
by Davtd K. Mt4lliner. Prepared for the ama- 
teur collector as well as the professional 
conchologist and malacologist, this exhaustively 
detailed work is the first reliable taxonomic 
treatment of the Muricidae since 1880. It offers 
many innovations in classification, and pro- 
vides descriptions, range data, and synonymy 
for some 390 species (15 described here for the 
first time). Illustrations include full-color 
photos of 456 specimens, 61 black-and-white 
drawings or photos, and 179 line drawings. 
Introduction, Glossary, Bibliography, Index. 

Marine Algae of 

Isabella A. Abbott & George J. Hollenberg. 
Contributions by specialists. This first complete 
systematic study of California seaweeds, an 
extension of G. M. Smith's classic Marine Algae 
oj the Monterey Peninsula, covers 80 percent 
of the species known from Alaska to Panama. 
Designed as a combined laboratory and field 
reference, it illustrates each of the 701 taxa 
treated by one or more line drawings, and 
includes comprehensive information for all 
species treated, an Introduction, a history of 
West Coast algal study by G. F. Papenfuss, 
maps, a Master Key to Genera, Glossary, 
Bibliography, Index. $2.2.. 50 

Stanford University Press 


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APRIL 25, 1977 



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Volume 91, number 2 — April 25, 1977 


Twila Bratcher 

Deshayes' Terebrid T>'pes in Ecole des Mines, Paris 39 

John H. Rodgers, Jr., Donald S. Cherry, et. al. 

The Invasion of Asiatic Clam, Corbicula manilensis, in the New River, Virginia 43 

Robert C. Wall 

Seasonal Movements of the Pond Snail, Lymnaea catascopium, in a Northern Lake 47 

Eva Pip 

Frequent Scalariformy in a Population of the Pond SnaW Zymnaea stagnalii 52 

Robert F. McMahon 

Shell Size- Frequency Distrihutions of Corbicula manilerisis Philippi from a Clam-fouled 

Steam Condenser 54 

M. G. Harasewych 

Abnormal Hyperstrophy in Littorina lineolata (Gastropoda: Littorinidae) 60 

Leroy H. Poorman and Forrest L. Poorman 

Four Opisthobranchs Living on Marine Algae from West Mexico 62 

Clement L. Counts, III 

The Miocene Bivalve Cumingia medialis (Semelidae) from South Carolina 66 

Tom M. Spight 

Latitude, Habitat, and Hatching Type for Muricacean Gastropods 67 

Walter 0. Cemohorsky 

Comis viola, a New Name for C. inolacea Reeve 72 

Tom M. Spight 

Is Tfiaiii canalicidata (Gastropda: Muricidae) Evolving Nurse Eggs? 74 

Branley A. Branson 

The Chinese Apple Snail, Cipangopaludina chinensis,on 

Orcas Island, Washington 76 

Fred G. Thompson 

The Polygyrid Genus McLeawm in Hispaniola 77 

Publications received v Recent Deaths 80 


Yonge. C. M. and T. E. Thompson. 1976. Liiing Marine 
Molluscs. 228 pp., 162 text figs., 16 color pis. A well-written 
textbook introduction, with the two opisthobranch chapters 
by T. E. Thompson. Distributed in the U.S. by Amerirnn 
Malai-nhKitsts. Publ., Box 42t)8, Greenville. De. 19807. $13.9.5. 

Alonso, M. R. 1975. Fauna Malocologica Terrestre de la Depre- 
sion de Granada (&pana). II. H Genero Helkella Ferussac, 
1821. Cuademos de Ciencias Biologicas Granada, vol. 4, no. 
1, pp. 11-28; I Pulmonados Desnudos, pp. 71-88. 

Warmuth, John H. 1976. The Biogeography and Numerical 
Taxonomy of the Oegopsid Squid Family Ommastrephidae 
in the Pacific Ocean. Bull. Scripps Institute Oceanography, 
vol.2;?,90pp. Paper.$:B..%. 

Paraense, W. Lobato. 1976. Helisoma trivolris and Some of Its 
Synonyms in the Neotropical Region (Mollusca: Planor- 
bidae). Rev. BrasU. Biol. 36(1): 187-204. 

Paraense, W. Lobato. 1975. Estado Atual da Sistematica dos 
Planorbideos Brasileiros. Arg. Mus. Nac. RJ, vol. 55, pp. 
105-128, 69 figs. Anatomy and shells well-illustrated. 

Abbott, R. Tucker (Editor). April 1976. ne Best of ne 
Nautilus. A Bicentennial Anthology of American Con- 
chology. viii + 280 pp., 1 color pi., text figs. American 
Malacologists, Publishers, Box 4208, Greenville, De. 19807. 
Hardback, $13.95. Presentation copy with slip box, $38.00. 

Hastings, Louise B. 1976. Index to the Taxonomic Names in 
Edwin A. Joyce, Jr., 1972, A Partial Bibliography of 
Oysters, with Annotations. Florida Dept. Natural 
Resources, St. Petersburg. Pamplet, 40 pp. Available from 
Delaware Museum of Natural History, Box 3937, Greenville, 
De. 19087, by sending 3 13-cent postage stamps. 

Quayle, D. B. 1975. Tropical Oyster Culture-A Selected 
Bibliography. 40 pp. (267 entries). International Develop- 
ment Research Center, Box 8500, Ottawa, Canada KIG 3H9. 

Gasull, Luis and Juan Cuerda. 1974. Malacologia del Conten- 
ido Gastrico de las Grandes E^trellas de Mar. Bol. Soc. Hist. 
Nat. Baleares. vol. 19, pp. 1,5,5-173, 3 pis. 

Franchini, Dario A. (EMitor). 1976. Simposio sui molluschi ter- 
restri e dulcicoli dell' Italia Settentrionale. Mantova. 102 
pp., 9 pis., text figs. 11 articles on such mollusks as 
Cingulifera, Ancylus. Lartetia. Paladilhiopsis and 

Tchang. Si, et al. 1975. A Checklist of Prosobranchiate 
Gastropods from the Xisha Islands, Guangdong Province, 
China. Studia Marina Sinica. no. 10 pp. 105-132, 7 pis. (7 
Nan-Hai Rd., Tsingtao, People's Republic of China). 

Handel, Klaus. 1976. Morphologie der Gelege und Okologische 
Beobachtungen an Buccinaceen (Gastropoda) aus der 
Siidlichen Karibischen See. Bonn. Zool. Beitr., vol. 27, pp. 
98-1X3. Also treats with fasciolariid and turbinellid egg cap- 
Hubendick, B. and A. Warren. 1976. Framgalade Srackor fran 
Svenska Vastkusten. Collection of 7 articles on the marine 
prosobranchs of Sweden. Excellent illustrations in this 
usefull handbook originally published 1969-1976. Box 11049, 
Naturhist. Mus., Goteborg, Sweden 400.30. 25 kronors. 

Shells and Shores of Texas 

By Jean Andrews 

This guide to the mollusks of the shallow marine 
waters of Texas and the Gulf coast is arranged 
according to the latest classification system, and 
each entry Is accompanied by an illustration. 
This book contains the clear, detailed depiction 
of more minute species than any other one 
source as well as one of the most extensive bibli- 
ographies in the field. 

512 pages, 24 color plates, 367 b&w photo- 
graphs, 77 line illustrations 
$19.95 through Dec. 31 , 1977; $24.95 thereafter 

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Vol. 91 (2) April 25, 1977 THE NAUTILUS 39 


Twila Bratcher 

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It has been well over a hundred years since 
Cierard Paul Deshayes published his descriptions 
of 95 new terebrid taxa. The 33 species published 
in 1857 in the Journal of Conchyliologie were 
written with surprising detail for that period. 
Those written by most of his contemporaries were 
sketchy descriptions in Latin and could fit any 
number of species. Deshayes followed his Latin 
descriptions with excellent word pictures in 
French of the species he was describing. Deshayes 
must have loved each species he described. He 
discussed them with such phrases as "beautiful 
and precious," "this very beautiful and 
remarkable species," "charming species." In one 
description he said, "All the shell is smooth, 
polished, shining as though it were made of 
porcelain." The figures in his 1857 monograph are 
exceptionally good in quality and detail. 

The 62 taxa Deshayes described in the Pro- 
ceedings of the Zoological Society of London, 
1859, are less easy to evaluate. Although the 
Latin descriptions are somewhat more detailed 
than most of that period, they were not followed 
by his fine French descriptions. They were 
published without figures. Some of the taxa were 
subsequently figured by Reeve. Some have never 
been figured. In all his descriptions Deshayes 
stated whether the material was from the Cum- 
ing collection, now in the British Museum 
(Natural History), or from his own collection, 
now in the Ecole des Mines, Paris. In 1944 in his 
"Deshayes Review of Terebra in the Journal of 
Conchology," Tomlin stated, "Probably there is 
more synonmy to be worked out with regard to 
Deshayes" new species. It would-be a great ad- 
vantage to get the types at the Ecole des Mines 

When I visited the Ecole des Mines in the 
spring of 1975, I located nine of the holotypes and 
one probable holotype in the Deshayes collection. 
Deshayes' detailed French descriptions, in addi- 
tion to his original measurements, made this task 

easier than it might have been. Because of his 
careful attention to detail, specimens differing 
substantially in measurement from those 
published by Deshayes could not be accepted as 
holotypes. An exception was Terebra eximia 
Deshayes, 1859. Deshayes' measurements were 92 
x 8 mm, which is evidently a misprint. The 
specimen which appears to be the holotype 
measures 46 x 8 mm. It is obvious that if a 
specimen of this species should reach a length 
should reach a length of 92 mm , the diameter 
would be greater than 8 mm. 

Some of the Deshayes taxa represented as be- 
ing from his own collection could not be found at 
all. The measurements of some differed substan- 
tially from the original Deshayes measurements, 
and are here considered paratypes. 


Terebra archimedis Deshayes, 1859, holotype, fig. 
1 & lA. Not previously figured. Dimensions 31 x 
5.8 mm. Original measurements 31 x 6 mm. In his 
description Dehayes stated that this species was 
representated in his collection only. Therefore I 
believe the specimen in the Ecole des Mines is 
the holotype rather than the specimen in the 
British Museum (Natural History) cited as the 
type by Cemohorsky (1969) which measures 32.7 
mm in length. Type locality unknown. This is 
conspecific with the Indo-Pacific species, T. 
funicidata Hinds, 1844, and T. langfordi Pilsbry, 
1921, as there are integrades between the forms. 
Schepman illustrated T. archimedis in his Siboga 
Expedition report, but the figure was of the 
funicidata form rather than the archimedis form. 

Terebra approximata Deshayes, 1859. No figure 
was published. Type locality unknown. Reeve con- 
sidered this taxa to be a junior synonym of T. un- 
dulata Gray, 1834, a fairly common Indo-Pacific 
species. No specimens of this taxa were found in 
the Deshayes collection . 


April 25.1977 

Vol. 91 

Terebra argeninllii Deshayes, 1859. No figure was 
published. Type locality unknown. Reeve places 
this taxa in synonymy with T. strigilata Lin- 
naeus, 1758. No specimens of this taxa were 

Terebra chilensis Deshayes, 1859, holotype, fig. 2. 
No figure previously published. Dimensions 40.2 .\ 
7.9 mm. Original measurements 42 x 8 mm. TVpe 
locality Chile. Tliis is a synonym of T. gemmidata 
Kiener, 1839, a rare species reported from Chile, 
Patagonia, and Brazil. 

Terebra chinensis Deshayes, 1859. No figure was 
published. Type locality is China Seas. Reeve con- 
sidered this conspecific with T. cingnlifera 
Lamarck, 1822, a common Indo-Pacific species. 
No specimens of this taxa were found. 
Terebra columnam Deshayes, 1859. No figure 
was published. Type locality unknown. Reeve con- 

FUJ. 1. Terebra archimedis IJeshayes. 18.59, holotype. 

FIG. 2. Terebra chilensis Deshayes, 18.59, holotype. 

FIG. X Terebra crassula Deshayes. 18.59, paratype. 

FIG. 4. Terebra crosxei Deshayes. 18,59. holotype. 

FIG. 5. Terebra exiniia Deshayes. 18.59, holotype. 

FIG. 6. Terebra mat heroniana Deshayes, 1859, holot>T)e on 

left, paratype on right. 

sidered this conspecific with T. cingulifera 
Lamarck, 1822, as did Tryon. No specimens of 
this taxa were found, 

Terebra crassula Deshayes, 1859, paratype, fig. 3. 
No figure was previously published. Dimensions 
23. 6 X 5.2 mm. Original measurements 27 x 7 
mm. Differences of measurements are sufficient 
that this must be considered a paratype. Type 
locality unknown. This is a synonym of Ha,'>tula 
hmtata (Gmelin, 1891), a common western Atlan- 
tic species. 

Terebra crossei Deshayes, 1859, holotype, fig. 4. 
No figure was published previously. Dimensions 
24 X 5 mm. Original measurements 23 x 5 mm. 
Type locality Indian Ocean, this is a synonym of 
Hastula penicillata (Hinds, 1844) a common 
Indo-Pacific species, 

Terebra difficilis Deshayes 1859. Figured by 
Reeve, Conch. Icon. vol. 12, pi. 18, fig. 86. Type 
locality unknown. Reeve said of this species, "a 
shell of solid growth, partaking somewhat of the 
character of T. laiDoefomm. in which the fine 
ribs are so crowded as almost to lap one on the 
other. It comes even nearer to T. souleyti " Tryon 
said it is conspecific with T. cancellafa Quoy & 
Gaimard, 18.32. No specimens were found in the 
Deshayes colletion. 

Terebra dispar Deshayes, 1859. Figured by Reeve, 
pi. 25, fig. 1.37. Type locality unknown. Reeve 
said, "shining-white, semi-transparent. Very 
closely resembles T. micans. " Tryon said it equals 
both cinerea (Bom, 1778) and aciculina (La- 
marck), two species which are quite distinct from 
one another. No specimens found in the Deshayes 

Terebra eximia Deshayes, 1859, probable 
holotype, fig. 5. Figured by Reeve, pi. 21, fig. 106. 
Dimensions 46.2 x 8 mm. Original measurements 
92 X 8 mm, evidently a typographical error. Type 
locality unknown. This is conspecific with T cor- 
rugata Lamarck, 1822. 

Terebra fimbriata Deshayes, 1857, holotype, fig. 
10. Figured by Deshayes, pi. 5, fig. 1. Length 88.6 
mm. Original measurements 88 x 19 mm. Type 
locality unknovwi. There is a paratype in the 
British Museum (Natural History). This taxa is a 

Vol. 91 (2) 

April 25, 1977 


junior synonym of T. crenulata Linnaeus, 1758. 
Terebra glabra Deshayes, 1857. Figured by 
Deshayes. Type of locality is China Seas. No 
specimen was found in the Deshayes collection in 
the Ecole des Mines. There is a specimen in the 
British Museum (Natural History) marked Type, 
T. glabra, which is obviously erroneous. Cemohor- 
sky (1969) pointed out that "The specimen pres- 
ent in the Cuming collection and measuring 43.3 
mm in length (original measurement 70 mm) is 
not the type; the holotype is probably in the 
Ecole des Mines in Paris". The specimen in the 
British Museum is a worn specimen of T. consors 
Hinds, 1844, and Tomlin said it equals T. consors. 
Deshayes said in shape, size, and coloration it 
more nearly resembles T. cingulifera Lamarck, 
1822. He also stated that the shell is all white or 
of a white washed with pale beige. He made no 
mention of the yellow blotches typical of T. con- 
sors. Tomlin made his evaluation from the 
specimen in the British Museum, and whether 
that specimen- is the same species as Deshayes' T. 
glabra probably will not be known unless the 
Deshayes holotype is found. 

Terebra histrio Deshayes, 1857. Figured by 
Deshayes. Type locality unknown. Reeve and 
Tomlin both mention that the type is cited from 
the Deshayes collection but that there was one in 
the Cuming collection which is merely a form of 
T. cormgata Lamarck, 1822. Neither Deshayes' 
description nor his figure is that of T. corTugata. 
No specimen found in the Deshayes collection. 

Terebra matheroniana Deshyes, 1859, holotype, 
fig. 6 paratype, fig. 6 (right). Not previously 
figured. Dimensions 17.4 x 3.3 mm. Original 
measurements 18 x 3 mm. Type locality Tahiti. 
TTiis is a species about which there has been 
much confusion. E. A. Smith considered it a good 
species and Tomlin agreed, citing Terebra lauta 
Pease, 1869 as a synonym. I agree with that. 
Reeve considered T. matheroniana a synonym of 
T. aciculina Lamarck, 1822, to which it bears no 

Terebra nbsoleta Deshayes, 1859, holotype, fig. 7. 
Figured by Reeve, pi. 21, fig. 107. Dimensions 38.9 
X 7 mm. Original measurements 40 x 7 mm. Type 
locality unknown. Reeve mentioned that this 
shell had indications of a brown band at the base 

FIG. 7. Terebra obsoleta Deshayes, 1859, holotype. 

FIG. 8. Terebra pundicidata Deshayes, 18.59, holotype. 

FIG. 9. Terebra splendens Deshayes, 1859, holotype. 

FIG. 10. Terebrafimbriata Deshayes, 1857. holotype. 

FIG. 11. Terebra subanguluia Deshayes, 18.59, holotype. 

FIG. 12. Terebra verreaun Deshayes, 1857, holotype. 

which may have faded during the last hundred 


Terebra puncticuLata Deshayes, 1859, holotype, 
fig. 8. Previously figured by Reeve, pi. 20, fig. 99. 
Dimensions 24.6 x 6.2 mm. Original measure- 
ments 25 X 6 mm. Type locality unknown. 
Synonyms: T flava Hinds, 1844 (non Gray, 1834); 
f. lutescens E. A. Smith, 1873. 

Terebra souleyeti Deshayes, 1859. Figured by 
Reeve, pi. 17, fig. 78. Type locality Gulf of Mexico. 
No specimens fotmd. 

Terebra splendens Deshayes, 1857, holotype, fig. 9. 
Figured by Deshayes, pi. 5, fig. 11. Dimensions 
73.8 X 12.6 mm. Original measurements 75 x 12 
mm. Type locality is China seas. This is T. 
dimidiata Linnaeus, 1758. 

Terebra semidecussata "Deshayes". This is 
evidently a manuscript name. It equals T 
dislocata (Say, 1822). 


April 25,1977 

Vol. 91 (2) 

Terebra subangidata Deshayes, 1859, holotype, 
figs. 11. Previously figured by Reeve, pi. 18, fig. 
87. Dimensions 33.6 x 6.8 mm. Original measure- 
ments 34 X 7 mm. Typ)e locality unknown. 

Terebra verremtxi Deshayes, 1857, holotype, figs. 
12 & 12 A. Figured by Deshayes, pi. 5, fig. 3. 
Dimensions 37.9 x 7.8 mm. Original measure- 
ments :38 X 9 mm. Type locality unknown. This is 
a synonym oiHastula strigilata (Linnaeus, 1758). 


I am indebted to the personnel of the Ecole des 
Mines in Paris, particularly Mme. E. Fatton, for 
the privilege of working with and photographing 
the Tcirhridac in the Deshayes collection and for 
help through correspondence since my return. I 
also wish to thank Sally Kaicher for her advice 
on shell photography and for her work in making 
prints for publication from my negatives taken at 
the Ecole des Mines; Dr. James McLean for his 
comments and suggestions regarding this man- 
uscript: and Dr. R. Tucker Abbott for the use of 
his picture of the holotype of Terebra fimbriata 


Bom, Ignatius von. 1778. Indei Rerum Naturalium Muxpi 

Casenrpl Vi iidnbonens-is. Part 1; Testacea pp. 1-458, 1 pit. 
Cernohorsky, Walter Oliver. 1969. List of Type Specimens of 

Terebridae in the British Museum (Natural History). The\0-2i. 
Deshayes. Gerard Paul. 1857. Descriptions de nouvelles especes 

du genre Terebra. Jmtr. de Conchyl. 6: 65-102, pits. 3-.5. 1859. 
Deshayes, G. P. 18.59. A general review of the genus Terehni. 

Rare and Exotic Specimen Shells 
for the discriminating collector 
Free price list 



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Bnjoklyn, New York 11236 USA 

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and a description of new species. Pnic. Zool. Sue. London, 
pp. 270-321. 

Gmelin. Johann Frederich. 1791. Carol! a Linne Systema 

naturae per regna tria naturae. Editio decima tertia. pp. 

Gray. John Edward. 1834. Enumeration of the species of the 
genus Terebra, with characters of many hitherto un- 
described. /Voc Zoal. Soc. Umdim for 1832, pp. 59-63. 

Hinds. Richard Brinsley. 1844. Descriptions of new Shells, col- 
lected during the voyage of the Sulphur, and in Mr. Cum- 
ing's late visit to the Philippines. [On new species of 
Terebra]. Proc. Zool. Soc. London for 1843, pp. 149-68. 

Lamarck, J. B. P. A. de M. de. 1822. Histoire naturelle des 
animaux vertebres, pp. 238-91. 

Linnaeus. Carolus. 1758. .Systema naturae per regna tria 
naturae. Eiiitio decima. reformata. pp. 741-42. 

Pilsbry, Henry Augustus. 1921. Marine Mollusks of Hawaii 
Vlli-XIII, Proc. Acad. Nat.. Set Philadelphia, pp. 300-09, pi. 

Reeve. Lovell Augustus. 1860. A monograph of the genus 
Terebra. Conch. Icon. vol. 12, Terebra, pis. 1-27. 

Reeve, Lovell A. 1860. A commentary of M. Deshayes's Revi- 
sion of the genus Terebra. Proc. Zool. Soc. London, pp. 

Say, Thomas. 1822. An account of some of the marine shells of 
the United States. Joitm. Acad. Nat. Sci. Philadelphia 2: 

Schepman, Matteus Martinus. 1912. The Prosobranchia of the 
Siboga Expedition, part 5, Toxoglossa, Terebra, pp. 369-77, 
pit. 25. 

Smith, Exigar Albert. 1873. Remarks on a few species belong- 
ing to the family Terebridae and descriptions of several 
new forms in the collection of the British Museum. Annals 
and Magazine of Natural History ll(4th): 262-71. 

Tomlin, John Read le Brocton. 1944. Deshayes' review of 
Terebra. Jam. Conch. 22: 104-8. 

Tryon, George Washington. 1885. Man. of Conch., vol. 7, 
Terebridae. pp. 3-64; 12 pis. 

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Vol. 91 (2) 

April 25, 1!»77 



John H. Rodgers, Jr., Donald S. Cherry, James R. Clark, 
Kenneth L. Dickson and John Cairns, Jr. 

Center for Environmental Studies 
and Department of Biology 
Virginia Polytechnic Institute and State University 
Blacksburg, Virginia 24061 


Corbicula manilensis appems to have successfully invaded the New River at 
Glen Lyn. Giles County, Virginia in 1975. Mean population densities of 18 Cor- 
bicula, m'^ were recovered doumstream from, a coal-fired generating plant while 
29 individuals m'^ were found immediately upstream. This seems to be the pre- 
sent limit of Corbicula immigration in the New River as no specimens were 
taken from .^ampliiig si fes farthe r upstream. Relationships between shell deniensions 
and shell weights, and viscera wet and dry weights were calculated from the 
one size "year class" present. Correlation coefficients ranged from 0.9683 for 
shell length and viscera wet weight to 0.6135 for shell dry weight and viscera 
dry weight. 


The present paper is the first report of Cor- 
bicula manilensis Philippi in the New River, 
Virginia, and to our knowledge, only the second 
report of Corbicula in this state (Diaz, 1974)'. Un- 
til recently, extensive investigations of benthic 
macroinvertebrates of the New River (con- 
sidered by many to be the second oldest river in 
the world) and its tributaries had not reported 
any specimens of this clam. The range extension 
of the Asiatic clam up this river is being careful- 
ly monitored, since the New River is an impor- 
tant source of water for various industries and 
municipalities. The biology of this organism and 
its relationships to other benthic and molluscan 
fauna can be studied, since pre-invasion data are 
available and this potential problem was revealed 
in its infancy. 

Forty specimens of Corbicula manilensis were 

' Tlie Delaware Museum of Natural History has numerous 
adult specimens collected in 1974 by Mrs. Betty Piech near 
Lanexa. Virginia, in the Chickahominy River which flows in- 
to the James River. 

randomly selected from quantitative collections 
starting on 12 October 1976, from sites above and 
below a coal-fired generating plant located on the 
New River at Glen Lyn in Giles County, Virginia 
(latitude-37°22'20", longitude-30°51'45", river 
mile 95) (Fig. 1). The upriver station was 
established 45 m above the intake pump station 
through which water is drawn for condenser cool- 
ing in the power plant. The plant generating 
capacity is approximately 300 MW with a max- 
imum of 340 MW. After passage through the 
plant, the heated water may be raised to a max- 
imum of 8 C above above ambient; however, dur- 
ing these collections there was a 3 C difference 
between the upriver and downriver stations (13 C 
and 16 C respectively). The substrate was 
characterized by gravel, sand and silt with sand 
and silt comprising minor portions (after Hynes, 
1970). The downriver station was located approx- 
imately 50 m below the pipe through which the 
heated water is discharged. The heated effluent 
was usually chlorinated three times daily to con- 
trol biofouling of the condenser pipes. At this sta- 
tion, the substrate ranged from cobbles and peb- 
bles to very fine sand with a predominance of the 
former. During sampling, water depth at both 


April 25.1977 

Vol. 91 (1: 

Stations ranged from 0.5 to 0.9 m with average 
flows of 18-21 cm see"'. Alkalinity (as CaCOj), pH 
and turbidity were 39 mg 1"', 7.80 and 35.0 
Jackson Turbidity Units, respectively. 

Samples were taken at each station using a 
0.25 m^ quadrant and a net to a depth of 15 cm. 
Clams were picked from each sample, counted, 
placed in water on ice and transported to the 
laboratory for further analyses. Travel time was 
less than two hours and samples were processed 
immediately. Dimensions and weights were deter- 
mined as described by Joy and McCoy (1975). 


FIG. 1. Kanawha River basin and sampling sites on the 
New River. X—Mud River, (hbell (.krunty. West Virginia; 
second report of Corbicula from West Virginia, 10 October 
1973 (Joy and McCoy. 197,5); h—Oielyan. Kanawha Qnmty. Virginin; first report of Corhicnld from West Virginia, 
17 July 196:1 -population had been established .iince 1961 by 
size "year class" data (Thomas and Mackenthun. 1961,1; 
C—den Lyti. (riles County. Virginia; Corbicula collected IJ 
October 1976 -pcrpulation had been estahlvihed since 197!> by 
size "year class" data (River Mile 95); D—Ltirich. (riles 
(hiinty, Virginia (River Mile 97); E— Narrows, (riles (hunty. 
Virginia (River Mile i(>2); ¥— McCoy, Montgomery County. 
Vi rgi n ia (Ri ver Mile 1 .11). 


The invasion rate of Corhieida in the Upper 
Ohio and Kanawha River Drainage basin can be 
estimated from available reports. Due to the 
distinctive morphology of the adults and larvae, 
the Asiatic clam is easily and likely to be 
distinguished from indigenous bivalves. A collec- 
tion of Corbicula reported from Chelyan. West 
Virginia, (Fig. 1) indicated, by size "year classes," 
that a population had been established there 
.since 1961 (Thomas and Mackenthun, 1964). A 
subsequent collection in Cabell County, West 
Virginia, was made in 1973 (Joy and McCoy, 
1975). If the downriver area is the source of pro- 
pagules for the population becoming established 
at Glen Lyn, Virginia, the clams would have 
traversed a distance of about 138 river miles in a 
period of 15 years, or an average rate of about 9 
miles year"'. Several physical barriers encoun- 
tered alone the suspected path of invasion include 
London Lock and Dam above Chelyan, Kanawha 
County, West Virginia, and Kanawha Falls and 
Bluestone Dam at Hinton, Summers County, 
West Virginia. This dam forms Bluestone Lake, a 
reservoir which is utilized for both flood control 
and hydroelectric power. The relatively rapid 
movement of the clam implies some augmenta- 
tion of its natural dispersive mechanisms. It is 
highly improbable that the nonparasitic plank- 
tonic veliger larvae would be capable of moving 
against the current at such a rate. Since no 
parasitic stage is present in the life cycle, a fish 
host would not be involved in dissemination 
(Sinclair, 1964). More likely, their movement was 
probably aided by fishermen as fishing pressure 
is relatively intense in this river system. Addi- 
tionally, transportation may have been provided 
by waterfowl since Clench (1970) stated that Cor- 
bicula may be able to pass through the intestinal 
tracts of ducks in viable condition. Live 
specimens are being sold and shipped to fish hob- 
byists around the country (Abbott, U)75). Subse- 
quent intensive sampling of the New River 
upstream from Glen Lyn at Lurich, Narrows and 
McCoy, Virginia, did not yield any specimens 
(Fig. 1). These results indicated that the clam had 
not yet been able to invade these areas. 

Based on approximations of age from shell 

Vol. 91 (2) 

April 25, 1977 


TABLE 1. Means l± S E) and ranges of parameters meaKured far Corh\cu\a sampled friiin upriver and dmenriver stations. 



Measured Pnrameler 





Shell Length (mm) 

9.8 ± 0.37 

7.2 - 12.3 

9.6 ± 0.32 

7.1 - 12.0 

Shell Width (mm) 

6.6 ± 0.27 

5.0 - 8.3 

6.6 ± 0.25 

.5.1 - • 8.4 

Viscera Wet Weight (mg) 

26.8 ± 1.34 

18.7 - .^5.1 

25.9 ± 1.09 

19.0 - 34.1 

Vise-era Dry Weight (mg) 

8.0 ± 0.45 

5.2 - 10.7 

8.7 ± 0.54 

5.7 - 14.6 

Shell Dry Weight (mg) 

105.4 ± 9.74 

8.9 - 141.1 

1066 ± 7.99 

8.3 - 140.9 

lengths (Joy and McCoy, 1975), it was apparent 
that the Corbkida collected at Glen Lyn were in 
their first year (Table 1). Most of these specimens 
were probably sexually mature (Gardner et al., 
1976) and should have been in the area since 
1975. Mean density at the downriver station of 18 
clams m"^ was significantly less (t-test, 0.05 level) 
than the mean density of 29 m'^ at the upstream 
station. This difference may be attributed to the 
influence of the power plant discharge or a 
substrate-associated distribution phenomenon. 
This subject as well as seasonal density dynamics 
will be further examined in future research. 

Least squares regressions (of the form y = a 
+ bx) and Pearson product-moment correlation 
coefficients (r) were calculated for ten relation- 
ships between shell dimensions and weights, and 
viscera mass weights (Table 2). All correlations 

TABLE 2. Regression analysis equations (y = a + bx) and 
correlation coefficients for various relationships between shell 
dimensions and weights, and wet and dry viscera weights of 


- Vaki. 

W = - 

- 0.1613 

+ 0.7072 L 


S= - 

- 92.5123 

+ 20.5729 L 


VWW = - 

- 6.5322 

-1- 3.4099 L 


VDW = - 

- 2.2559 

-1- 1.0988 L 


S = - 

- 55.0134 

-1- 1.0988 L 


VWW = - 

- 1.4196 

-1- 4.2002 W 


VDW= - 

- 2.5536 

-1- 1.6476 W 


VWW = 


-1- 0.10(»S 


VDW = 


-1- 0.0345 S 


VDW = 


+ 0.ia34VWW 


'W = width of shell (mm) 

L = length of shell (mm) 

VWW = wet weight of visceral mass (mg) 

VDW = dry weight of visceral mass (mg) 

S = dry weightof shell (mg). 

' Significance level, P = 0.0001. 

were highly significant (P<0.01) although the cor- 
relation coefficients were slightly less than those 
of Joy and McCoy (1975). This can be explained 
by the variability associated within the one size 
class in this study compared with a range of size 
classes (from about one to more than four years) 
collected by Joy and McCoy (1975). It is in- 
teresting to note that the width of their 
specimens averaged about 66% of the clams' 
lengths which agreed closely with the average of 
70% in this study. Sinclair and Ingram (1961) 
reported somewhat different morphology in 
specimens from the Tennessee River (shell width 
about 89% of length based on their published 
photographs). Only the correlation between shell 
length and viscera wet weight was greater in this 
study (r = 0.9683) than in the investigation of 
Joy and McCoy (1975) (r = 0.9407). Results of this 
study agreed with the observation of Joy and Mc- 
Coy (1975) that viscera wet, rather than dry, 
weight correlation coefficients are greater and in- 
dicate that noncombustible mineral uptake 
varied more per individual than water content. 

It is anticipated that the impact of Corbicula 
on this river system will be exhibited primarily 
in two different areas: 1) decline in populations 
of other bivalves as seen during the invasion of 
the Altamaha River in Georgia (Gardner et al., 
1976); and 2) increase in problems associated 
with industrial and municipal water use (Sin- 
clair, 1964, 1971). The survival of indigenous 
species of Margaritifera, Tristigonia, Elliptio, 
Sphaerium and Piddium in the New River ap- 
pears to be seriously threatened. 


Appreciation is expressed to James H. Ken- 
nedy, Biology Department, Virginia Polytechnic 
Institute and State University, for confirming 


April 25,1977 

Vol. 91 (2) 

identification of Corbicula and to employees of 
Applachian Power Company's Glen Lyn Plant for 
cooperation during the river collections. 


Abbott. R. Tucker 197.5. Beware the Asiatic Freshwater Oam. 

Tropical Fish Hnhhi/ist. 23: 1.5 (Feb.). 
Clench. W. J. 1970. Corbicula manilensis (Philippi) in lower 

Florida. The Nautilus 84(1): 36. 
Diaz, R. .J. 1974. Asiatic clam, Corbicula manilensis (Philippi), 

in the tidal .James River, Virginia. Chesapeake Sci. 15(2): 

Gardner, J. A., Jr., W. R. Wo<xiall, Jr., A, A. Staats, Jr. and J. 

F. Napoli. 1976. The invasion of the Asiatic clam {Corbicula 

manilensis Philippi) in the Altamaha River. Georgia. The 

NautUus90{:i]: 117-12.5. 

H>Ties, H. B. N. 1970. The Ecology of Running Waters. Univ. 
of Toronto Press, Toronto. 555 pp. 

Joy, J. E. and L. E. McCoy. 1975. Comparisons of shell dimen- 
sions and viscera mass weights in Corbicula manilensis 
(Philippi, 1*4«). The Nautilus 89(2): .51-.54. 

Sinclair, R. M. 1964. Clam pests in Tennessee water supplies. 
Jour. Amer. Water Works Assoc. 56: 592-599. 

Sinclair, R M. 1971. Annotated bibliography on the exotic 
bivalve Corbicula in North America, 1900-1971. Sterkiana 

Sinclair, R. M. and W. M. Ingram. 1%1. A new record for the 
Asiatic clam in the United States, the Tennessee River. The 
Nouh/iAs 74(3): 114-118. 

Thomas, N. A. and K. M. Mackenthun. 1964. Asiatic clam in- 
festation at Charleston, West Virginia. The Nantilux 78(1): 

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Vol. 91 (2) April 25. 1977 THE NAUTILUS 47 


Robert C. Wall 

Division of Mathematics and Science 

Lake-Sumter Community College 

Leesburg, Florida 32748 


These data from a 3-year study in Lake Ann, located north of Interlochen in 
the northern Lower Peninsula of Michigan, indicate that the freshwater 
pulmonale snail Lymnaea catascopium (formerly L. emarginata) does not 
migrate into deep water with the approach of winter. Tfii^'i behavior pattern dif- 
fers from that reported by Cheatum (1931t). The observations indicate that while 
these snails do move within the popdation, their movements are random in 
nature with no tendency to migrate into deeper off-shoal water in the fall. If 
anything, the data collected actually show their movements were more toward 
shore than away from it. The difference in migration reported could be due to 
differerwes in the periods the observations were made. The studies by Cheatum 
and Brackett were primarily in late summer, early fall, and late spring; thw 
study covered all seasons in the course of 3 years, i.e.. late fall winter, and 
early spring as ivell as the periods designated by Cheatum and Brackett. It was 
established that while there were snail movements within the population as ex- 
hibited by L. catascopium during the winter, those movements were random in 
nature, and not migratory. 

INTRODUCTION migration patterns of pulmonate snails in 

Some pulmonate snails that inhabit temperate Douglas Lake. The following information was 

lakes are known to migrate from shallow into obtamed durmg a 3-year study of Lymnaea 

deeper water with the onset of cold weather in catascopium Say, 1817 (of which L emarginata 

the fall; they return from deeper water onto Say, 1821, is a synonym, fide H. J. Walter, 

shoals of the lakes in the spring. This pattern of 1969). The observations were made in Lake 

migration has been assumed to be normal for ^nn, north of Interlochen in the northern I^wer 

most of the larger pond and lake snails and Peninula of Michigan to determine whether this 

malacologists assumed it was the usual pattern. ^nail shows any appreciable seasonal migratory 

However, data obtained in a 3-year study in- movement. 

dicates that the seasonal migration of at least Snails involved in the transmission of a skin 

one species does not follow that pattern. disease in the Great Lakes region known as 

Earlier work by Cheatum (1934) in Douglas schistosome dermatitis or swimmers' itch, are 

Lake, Cheboygan County, Michigan indicated often in colonies or "beds" covering fairly exten- 

there was seasonal movement of several aquatic sive areas in shallow water (less than 1.5 meters 

gastropod species which he interpreted as in depth). Assuming a seasonal migration takes 

"migration." Later, Brackett (1940) concluded place and the host snails migrate into deeper 

that snails he observed did not have an annual water in the fall to assemble in smaller and 

migratory cycle, but remained "year round in restricted profundal areas, control could then be 

the vicinity of where they hatched." Un- easier, more efficient, and less costly. Under 

fortunately, neither Cheatum nor Brackett ob- those circumstances less damage would occur to 

tained winter data from Michigan's northern the biota in the lake than with the treatment 

lakes. More recently, Clampitt (1972a,b) studied methods currently utilized. The best method of 


April 25.1977 

Vol. 91 (2) 

control would involve applying chemical treat- 
ment just after fall migration or early in spring 
before the snails come back into shallower 
water. Such considerations tend to stress the im- 
portance of resolving the controversial question 
as to whether host snails migrate or not in the 
seasonal way described. 


This investigation was started August 1966 
and terminated in June 1969 at the beginning of 
the annual breeding season of Lynniaea 
catascopium. During the summer of 1966 an ex- 
tensive survey was undertaken in the Lower 
Peninsula of Michigan to determine which lakes 
were reported to have outbreaks of schistosome 
dermatitis. Among them, Lake Ann, Benzie 
County, had on its northern shoal a thriving 
colony of Lymnaea (Stagnicola) catascopium. 
the snail reported by Cort (1950) as a principal 
vector of schistosome dermatitis. Although 
"swimmers' itch" was reported in that lake and 
copper sulphate treatment had been applied, 
several years had intervened prior to this study, 
so that the snail population had again become 
well established. 

Lake Ann is 13 miles southwest of Traverse 
City, Michigan in Benzie County, T. 27N, R. 
13W, Sections 22, 23, 26 and 27, and covers 515 
acres; its maximum depth is 23 meters. The bot- 
tom of the lake, at about 12 meters in depth, is 
covered with a pulpy peat. In the more shallow 
areas marl covers the bottom; a narrow band of 
sandy shore occurs only along the north and 
east with a long stretch of beach to the west. 
The snails studied were on a sandy shoal along 
the north side of the lake where they were most 
abundant in the area extending from shore to 8 
meters out into water up to 0.5 meters deep. 
Snail density near shore averaged 240 per square 
meter; it declined sharply with increased depth 
of water, so that beyond 39 meters from shore 
and at depths greater than 1.5 meters, snails 
were scarce. Using a motor boat and wire-mesh 
dredge, quadrat sampling was made from 1.5 
meters of depth to 12 meters of depth; however, 
no live specimens of L. catascopium were 
recovered. The snail bed clearly was confined to 
that shallow shoal area. 


The First Year: Trips were made from Ann 
Arbor to the study area at Lake Ann on a 
schedule as follows: August 15, September 25, 
October 6 and 25, and November 17, 1966; 
January 24, March 28, April 27, June 1, July 12, 
and September 28, 1967-a total of 11 trips dur- 
ing the first year of the study. On October 25, 
1966, 1280 snails were marked with red nail 
polish covered by lacquer. Specimens varied in 
size from 11 to 22 mm in length (measured from 
apex to base of aperture). As soon as the mark- 
ings were dry, the snails were returned to the 
area from which they were collected and scat- 
tered randomly over the snail bed. 

During the periodic visits to that site in the 
fall, winter and spring of 1966 to 1967, it was 
clearly evident that, contrary to information ob- 
tained from Cheatum's earlier studies, these 
snails did not exhibit a seasonal migration. 
While they tended to "group" in two's or three's, 
there was no mass movement of that population 
into deeper water as compared to their position 
on the shoal area then inhabited during August. 
Observations made of their position on the 
shoals and under the ice during January and 
March 1967 also indicated that they remained in 
the same area inhabited during that fall and 
winter. In January and March a thick ice cover 
was found on the lake except for a strip about 3 
meters wide along the shore. Snails were seen 
from the water's edge outward. Since the opa- 
queness of the ice made observations through it 
impossible, a hole was chopped and live snails 
were seen on the substrate. Many of the marked 
snails were observed among others in the open 
water near shore; however, none of the marked 
individuals were seen through the hole in the 
ice. Although the red nail-polish on the marked 
snails had faded badly, it still was visible. In 
April, soon after the ice had melted, a quadrat 
sampling was made using a wire dredge. Sam- 
ples were taken at approximately 25 meter inter- 
vals from near shore (in a southwesterly direc- 
tion) out into water 12 meters deep. The total 
distance of the quadrat was about 350 meters. No 
snails other than a few small Campeloma 

Vol. 91 (2) 

April 25, 1977 


decisum were recovered in water deeper than 2 

The number of marked individuals seen dur- 
ing the June visit was estimated to be about 10 
per cent of the sample marked. By this time the 
nail polish had almost completely faded making 
it extremely difficult to distinguish marked from 
unmarked individuals. Even with the aid of a 
glassbottom bucket, wave action made observa- 
tion difficult in shallow water. 

Very few (about 5 per cent) of the marked, 
dead (shells) were recovered during the April and 
June visits. Possible explanations for the small 
percentage of "sightings" of marked individuals, 
both living and dead, are: fading of the nail 
polish made them difficult to spot; many in- 
dividuals were almost completely buried in the 
substrate; disappearance as caused by various 
snail "predators;" marked individuals may have 
been selected because of their conspicuousness; 
marking materials may unknowingly have been 
toxic to the animals; wave action which tended to 
be quite severe on this shoal made seeing them 
difficult. For whatever reason, the true 
significance of this study was finding marked 
animals only in the immediate vicinity of the 
shoal where they had been placed rather than 
where these snails were subsequently recovered. 
Although during the 3-year period numerous 
checks made in all directions from the area in 
which marked individuals were placed. No 
marked individuals, living or dead, were ever 
found more than 2 meters from the shoal on 
which snails had been placed. 

The Second Year: Based on information ob- 
tained during the first year, the frequency of 
visits to the study area during the next 2 years 
was reduced from 11 to 5 trips. However, 
throughout the 3 years, observations were made 
at the study site every month of the year except 

In October of the second year, 3 study 
quadrats, each covering one quarter square 
meter, were laid out as follows: Plot I, 14 meters 
from shore in water .12 meters deep; Plot II, 27 
meters out in water .51 meters deep; and Plot III, 
39 meters from shore in water .69 meters deep. 
These measurements were made from the shore 

to each study plot, compass readings were made, 
and onshore landmarks were recorded so that 
several criteria were available to help relocate 
the study plots on subsequent visits. The purpose 
of these quadrats was to determine whether the 
snails moved around within the larger snail bed. 
The number of snails in each of the 3 plots was 
counted and a sample of 15 snails per plot was 
marked with red India ink and then returned to 
their respective plots. Because of its longer 
lasting quality, India ink was used instead of the 
nail polish to mark those shells. There were 115 
snails in Plot I; 41 in Plot II; and 35 in Plot III. 
During subsequent visits the number of marked 
and unmarked snails per plot was determined. 
Visits to the study area were made on November 
16, 1967; February 14 and May 15, 1968. 

During the November visit the weather was 
cold (air temperature 1.5''C, water temperatue 
3.0°C) and windy. Many snails were tossed about 
by wave action, others were observed buried to 
various degrees of submergence in the substrate: 
only 2 snails (unmarked) were seen in Plot I; 
some may have been buried in the substrate. In 
order not to disturb the study plot, it seemed ad- 
visable not to dig into the substrate. Two marked 
snails (13.2% of the sample placed in this area) 
were sighted .5 meter from Plot I toward shore; 
12 snails, including 2 marked individuals, were 
seen in Plot II. Two additional marked snails were 
found .3 meter inshore from Plot II. Thus, 26.4% 
of the marked snails placed in this area were 
seen. Fourteen snails were observed in Plot III, 
none of which had been marked. Two marked 
specimens were observed .3 meter inshore from 
this plot. The area around each study plot, out to 
a distance of 3 meters, was checked. No other 
marked snails were seen. Although more speci- 
mens were observed outside the study plots than 
inside, they were less numberous everywhere 
than in October. Many were now buried in the 

During the following February a heavy ice 
cover was on the lake ranging from 5 cm at the 
shoreline to 45 cm at 27 meters from shore. 
Although snails were seen at the shore and 
through a hole chopped in the ice 27 meters from 
shore, no marked snails were seen during this 


April 25,1977 

Vol. 91 (2) 

visit. On May 15, the air temperature at Lake 
Ann was 25.5°C and the water temperature was 
16.0°C. Only one marked snail (6.6% of the 
marked sample) was found in the area around 
Plot I; it was 3 meters west of the plot. Three 
marked animals (19.8% of the sample placed in 
Plot II) were found inshore within 5 meters of 
Plot II. None of the marked snails placed in Plot 
III was found. Since all snails had been marked 
with the same color of India ink, there was no 
way to determine the plot from which they had 
come. As expected in terms of the annual cycle, 
population density again dropped drastically 
from an average of 240 per square meter in Oc- 
tober to an average of 30 per square meter in 
mid-May. Population densities were greatest near 
shore and declined rapidly toward deeper water 
during all of the months in which observations 
were made. 

The results of the first year were again 
substantiated since these snails did not migrate 
into deeper water off the shoal, but remained 
where they had been during summer and fall. 
While there were movements of snails within the 
population, it was impossible to determine 
whether these movements gave evidence of a pat- 
tern or were of a random nature. 

The Third Year: Based upon the studies of the 
first and second years, some innovations were 
made this third and final year of investigation. 
The three established quadrat plots were left in- 
tact. Three samples, each with 200 individuals, 
were marked but a different color of a paste In- 
dia ink was used for each of the samples. Sample 
one was yellow; sample two, red; and sample 
three, blue. Specimens in sample one (yellow) 
were then scattered in a 20 meter radius arc in 
the study Plot I, some 14 meters from shore; the 
sample two (red) snails were scattered in a 30 
meter arc in Plot II at a distance of 27 meters 
from shore; and the sample three (blue) snails 
were likewise scattered in a 40 meter arc in Plot 
III at 39 meters from shore. Care was taken to be 
sure that these samples passed through each of 
the 3 earlier study quadrats established during 
the second year of the study. This arrangement 
served to determine the extent to which the 
snails ranged within the total population area. 

The 3 snail samples were marked October 25, 
19()8. Subsequently, 3 trips to examine the extent 
of movement were made to the study area on 
March 7, April 19 and June 16, 1969. An unfore- 
seen accident made visits to the study area im- 
possible during December or January as original- 
ly planned. 

By March 7 the air temperature was 4.0°C and 
the water was 4.5°C. TTie lake was still covered 
with a thick cover of ice except for a strip about 
6 meters wide along the shore. Although all 3 
study plots were ice covered, 4 yellow-marked 
snails (2% of the total sample) and numerous un- 
marked animals were seen in that open water. 
The population density again had decreased con- 
siderably as in the previous 2 years. 

On April 19 it was ascertained that the ice on 
that lake disappeared about April 15. The air 
temperature on the 19th was 15.0°C, the water 
was 5.0°C. Using a glass-bottom bucket and the 
distance guide used for setting the 3 plots, a 
careful survey was made in each area. Dredgings 
were made with sweeps on the arcs established 
for Plots I, II and III; additional sweeps were 
made at 1 meter intervals between plots. Only 
those snails marked with the color designated 
within the plot distances (Plot I, yellow; Plot II, 
red; Plot III, blue) were found within the plot 
arcs. With but one exeption, all marked snails 
observed at other than the plot arc distance from 
shore were inshore from their respective plot 
arcs. The exception was 2 red-marked individuals 
found 3 meters out from the Plot II distance arc. 
A total of 77 per cent of the marked snails 
recovered were at plot arc distance from shore, 19 
per cent were inshore from their plot arc 
distance, and only 4 per cent of the marked snails 
recovered were out beyond their plot distance 
arc. Of the 2(K) yellow marked specimens 23 or 
11.5% were seen on this visit; 13 or 6.5% of the 
2(H1 red: and 17 or 8.5% of the blue were found. 

During the final visit on June 16, the air 
temperatue was 22.0"C; the water was 21.0°C. A 
general survey of the whole snail bed revealed 
that most adult snails had already died. Many 
shells had eggs attached to them; however, no 
young snails were found. As during the April 19 
visit, a careful survey was made of the studv 

Vol. 91 (2) 

April 25, 1977 


area. In sweeps made at 1 meter intervals from 
shore outward to 2 meters beyond the Plot III 
distance from shore, very few live sails were seen 
and but a few shells. The following marked shells 
and 1 live, marked snail were found: 1 yellow 
shell at Plot I arc distance from shore; 1 red shell 
1 meter inshore from the Plot II arc distance: 1 
blue shell 3 meters inshore from Plot III arc; 1 
blue shell 2 meters inshore from Plot III arc 
distance; 1 live blue marked near Plot III; and 2 
blue marked shells (one with eggs attached) 2 
meters out from Plot III arc distance from shore. 


The investigation was supported (in part) by 
PHS Training Grant No. 5 TI 41 from the Na- 
tional Intitute of Allergy and Infectious Diseases, 
U.S. Public Health Service, Washington, D.C. 

The assistance of Henry van der Schalie and 
Elmer G. Berry, curators in the Mollusk Divi- 
sion, Museum of Zoology, University of Michi- 
gan is gratefully acknowledged. The work in the 

field was supported by several members of the 
Mollusk Division and my family. 


Brackett, Sterling. 1940. Studies on schistosome dermatitis. 

VIII. Notes on the biology of the snail hosts of schistosome 

cercariae in Wisamsin and epidemiological evidence for life 

cycles of some avian schistosomes. Amer. J. Hyy.. 32: 85-104. 
Cheatum, Elmer P. 1934. Limnological investigations on 

respiration, annual migratory cycle, and other related 

phenomena in fresh-water pulmonate snails. TVan.s. Micros. 

Soc. 53: 348-407. 
Clampitt, P. T. 1972a. Seasonal migrations and other 

movements in Douglas Lake pulmonate snails (Abstract). 

Malacol. Review, 5(1): 11-12. 
Clampitt. P. T. 1972b. Seasonal migratory cycle and related 

movements of the freshwater snail Physa integra 

(Pulmonata: Basommatophora) (Abstract). Bull. Ecol. Soc. 

.4mpr.. 53(2):21. 
Michigan Department of Natural Resources. Institute for 

Fisheries Research. 1950. Lake Inventory Map: Lake Ann. 
Wall, Robert C. 1968. An analysis of the current status of 

schistosome dermatitis problem in Mighigan. Doctoral 

Thesis. University of Michigan. 
Walter. Harold J. 1969. Illustrated biomorphology of the 

"angulata" lake form of the Basommatophoran snail. Li/m- 

luwn ratn.'^rdpiiim Say. Mnlncnl. Rev.. 2: 1-102. 



C. M. Yonge and T. E. Thompson 


Two distinguished British marine biologists have combined their knowledge and talents to 
produce a compact, well-rounded account of the largest marine group of animals. 

"The first modem book on the biology of marine mollusks 
that is of textbook quality, yet so beautifully written 
and illustrated that the legions of amateur conchologists 
will readily absorb its wealth of information"— R. Tucker 
Abbott, Ph.D. 

Send check or money order to: 
American Malacotogists, Publ. 

P.O. Box 4208 
Greenville, De. 19807 U.S.A. 



Cldthbound, 288 pp., 162 text figures, 16 plates with 18 glorious color photographs of living 
marine molluscs. Only $13.95. 


April 25,1977 

Vol. 91 (2) 


Eva Pip 

Department of Botany 

University of Manitoba 

Winnipeg, Manitoba 

Canada R3T 2N2 


T7VI) populations of Lymnaea stagnalis that had been exposed to chronic low- 
level (jammn radiation in situ were examined for the presence of shell ab- 
normalities. One population shoived no abnonnalities. In the other population 
sea la ri form y UHhs found at a frequency of 0.5%, and occurred nmsi.-itentlij in ini- 
tiallti non-scalar shells. Gnmnin mdintinn )'.s apparently nut a direct cause if 

Scalariformy in natural populations of Lym- 
naea stiujuulis (Linnaeus) is normally a rare and 
isolated occurrence, the causes of which are 
unknown. Studies of this phenomenon are dif- 
ficult because of the very few, scattered and poor- 
ly documented specimens known to be in ex- 
istence (Pip, 1975) and because the probability of 
recurrence in wild populations that have pro- 
duced such individuals is too low to merit obser- 
vation. However there is evidence that popula- 
tions showing a relatively high frequency of 
scalariformy exist. F. C. Baker (1911) cited a 
population sample from Spoonbill Slough, Deuel 
County, South Dakota, that contained several 
scalariform individuals. This study documents the 
discovery of another such population of L. 
stmjncdis. Perhaps coincidentally, this population 
has been exposed to chronic low-level gamma 


The study sites were located in an area, 1 km 
in diameter, of mixed boreal forest that had been 
reserved in the late 1960's for a radiation ecology 
study within the Whiteshell Nuclear Research 
Establishment's controlled area near Pinawa in 
eastern Manitoba. Chronic gamma radiation 
began in early 1973 by a 10,000 effective curie '" 
Cs source located at the top of a 20 m tower 
placed at the center of the area (Dugle and 

Thibault, 1974). Irradiation continued at an 
average of 19 hours per day. By the end of 
August, 1975, the area had received a total of 
17,000 hours of irradiation. The western portion 
of the area contained numerous small shallow 
ponds that had originated as gravel excavations 
prior to 1965. Of these ponds, two contained 
populations of Lymnaea stagnalis, their centers 
located 300 m (site 1) and 480 m (site 2) from the 
irradiator respectively. Site 1 was densely col- 
onized by cattails (Typha latifolia); small patches 
of open water contained the pondweeds 
Potamogeton gramineus, P. pectinatus and P. 
nutans (nomenclature after Scoggan, 1957). The 
mean dose rate at site 1, estimated during the 
growing season by lithium fluoride dosimeters 
placed 1 m above the center of the pond's surface, 
was 12.428 mrad/h. Site 2 was much more ex- 
posed: there was no emergent vegetation except 
for one small stand of cattails. The sparse 
submerged vegetation consisted of Potamogeton 
fnliosvs and a species of the algal stonewort 
Chara. The mean dose rate 1 m above the center 
of the pond's surface was 3.082 mrad/h. Because 
of the pond's exposure, water temperatures dur- 
ing midsummer reached 30 C. Although both 
ponds were less than 1 m deep, temperatures at 
site 1 were consistently lower because a large 
proportion of the water surface was shaded. Sur- 
face water samples collected in July, 1975 were 
analyzed according to methods recommended 

Vol. 91 (2) 

April 25, 1977 


by the American Public Health Association 
(1971). The two sites showed few differences in 
the monitored variables: pH 7.7 - 8.7, total 
filtrable residue 135 mg/1, alkalinity 80 mg 
CaCOj/l, sulphate mg/1, chloride mg/1, nitrate 
1 mg/1, orthophosphate 2 mg/1 (site 1) and 7 
mg/1 (site 2). Besides L. xtagnali.^ site 1 also con- 
tained Staynicola pal ustris while site 2 contained 
S. palustris and Physa gyrina. 

During the 1975 season all visible live and dead 
individuals of L. stagnalis at the two sites were 
scored for presence or absence of shell ab- 
normalities. Individuals of other species were ex- 
amined as well. 


The small populations of L. stagnaliji and S. 
palustris at site 1 showed no evidence of mor- 
phological abnormalities. The larger population of 
L. stagnalis at site 2 showed a constant frequency 
of scalariformy during the 1975 season of 5 per 
1000 individuals. Scalariformy occurred con- 
sistently in initially non-scalar shells (Fig. 1), a 
characteristic noted in previous reports (Pip and 
Paulishyn, 1970; Jackiewicz, 1972; Pip, 1975). 
Onset of scalariformy was abrupt and well- 
defined. In approximately 75% of the affected in- 
dividuals, scalariformy commenced in the fourth 
and fifth whorls. In the remainder of specimens 
scalariformy was apparent earlier; in some in- 
dividuals it occurred as early as in the second 


FIG. 1. Scalariform shells of Lymnaea stagnalis cnlleeted nt 
site 2 in Manitoba, Canada, during 1975. i'/> 

whorl. One specimen showed onset of scalari- 
formy in the sixth whorl; this was the only 
specimen where mechanical injury to the shell 
was apparent. Scalariformy was frequently ac- 
companied by curvature or breakage of the shell 
axis. Other aberrations were not observed in L. 
sta/inalis. The small populations of S. palustris 
and P. gyrina at site 2 were morphologically nor- 

The unusually high frequency of scalariformy 
at site 2 is difficult to explain. Because site 1 
received 4 times the mean dose rate of site 2, 
with no scalariformy or other abnormalities 
recorded, radiation appears to be an unlikely 
direct cause. Radiation may have contributed 
towards the stress already placed on the 
organisms by elevated temperatures. The two fac- 
tors are related in that elevated temperatures in- 
crease the time breathing at the surface 
(McDonald, 1973). Since attenuation of radiation 
with increasing water depth is considerable, the 
snails are exposed to the maximum dose rate 
when they are at the surface. The additional ex- 
posure to radiation, combined with the effects of 
heat stress, may result in some disturbance to 
growth. Because scalariformy occurs, as a rule, 
relatively late in the development of the snail, 
the causative agent is not operating at the 
nuclear level. Verdonk (1973) has shown that in 
L. Stagnalis few gene deficiencies become active 
beyond the veliger stage. It is therefore likely 
that mechanical or physiological agents are 
among the responsible factors. The occurrence of 
Cham at site 2 is interesting in that Geyer (1929 
in Jackiewacz, 1972) and Pip (1975) have noted 
the presence of this alga in habitats where 
scalariform snails have been collected. Further 
study is necessary before this phenomenon is 


I would like to thank Drs. J. Dugle and J. 
Guthrie of the Whiteshell Nuclear Research 
Establishment for their advice and encourage- 
ment during the pursuit of this problem. 


April 25.1977 

Vol. 91 (2) 


American Public Health Association. 1971. Standard Method'^ 
for the Eiaminatifm of Water and Wastewaters.^. 874 pp. 

Baker. F. C. 1911. The Lymnaeidae of North and Middle 
America. Ot icago Acad. Sri. Spec. Pub. No. .y. 539 pp. 

Dugle. J. R. and D. H. Thibault. 1974. Ecology of the Field 
Irradiator-Gamma area, 111. Revisions to botanical methods 
and vegetation sampling procedures (AECL-41.3.5). Atomic 
Energy of Canada Limited, report AECI^4668. 41 pp. 

Jackiewicz. M. 1972. Anormalnosci w budowie shorupki 
niekorych mi^zakow wodnych. Przeglad Zoologiczny 16:1: 
95-98. (in Polish). 

McDonald, S.C. 1973. Activity patterns of Lymnaea atagnalis 

(L.) in relation to temperature conditions: a preliminary 

study. Malacolngia 14: 39,5-396. Abstract only. 
Pip, E. 1975. Scalariformy in the pond snail. Li/mnaea 

stagnalis. The Nautilus 89: 36-37. 
Pip, E. and W. F. PaulishvTi. 1970. Unusual fr«sh water 

mollusk collected. Hawaiian Shell News 18: 11: 6. 
Scoggan, H. J. 19.57. Flora of Manitoba. Nai. Mus. Canada, 

Bull. No UO, 619 pp. 
Verdonk. N. H. 1973. Gene expression in early development of 

Lifmnof a stagnalis. Devel. Buil. 35: 29-35. 




Robert F. McMahon 

Department of Biology 

TTie University of Texas at Arlington 

Arlington, Texas 76019 


Specimens and empty whole and half ahelh of the introduced Asiatic freshwater 
clam. Corbicula manilensis, were collected from the inlet (cold water) box. con- 
denser tubes and outlet (warm water) box of a clam-fouled steam condenser of an 
electric generator utilizing raw water from Lake Arlington, Texas. Size-frequency 
distributions of length, height, and width of shells removed from these three sec- 
tions indicated that the clams were not growing in the condenser but had been 
carried into it with intake currenUi from an external population in the intake em- 
bayment and tunnel. It appers that the condenser tubes acted as a sieve becoming 
fouled only unth shells of an appropriate size to become lodged in the tubes while 
smaller specimens passed thnmgh and larger shells were retained in the inlet box. 
It is siHjge.'ited that increasing tube inside diameter to 29.0 mm or mitre icill (illmr 
even the largest specimens of C. manilensis to /la.w thnoigli cinidniscrs mid 
therehii a void fouling problems with th /.s' species. 

The introduced Asiatic freshwater clam, Cor- 
bicula manUetisis. was first recorded in the Col- 
umbia River, Washington, in 1938 and has since 
spread through a large portion of the freshwater 

' Supported by grant number 16-6.53 from Organized Research 
Funds of The University of Texas at Arlington to Robert F. 

environments of the southern United States 
(Sinclair, 1971, and references within). The high 
reproductive capacity and fast growth of this 
clam has allowed it to become a major pest 
species in many drainage systems (Ingram, 1959; 
Sinclair and Isom, 1961. 1963; Sinclair, 1963, 1964, 
1970; Prokopovich and Herbert, 1965; Prokopo- 
vich, 1969). Recently C. manilensis has been 

Vol. 91 (2) 

April 25, 1977 


reported to have fouled raw watercooled steam 
condensers of electric generating and other in- 
dustrial facilities in several regions of the United 
States (Ingram, 1959; Sinclair and Isom, 1961. 
1963: Sinclair, 1963, 19&4, 1970; Thomas and 
MacKenthun, 1964; Thomerson and Myer, 1970; 
Diaz, 1974). This report describes the distribu- 
tions and means of shell size for specimens of C. 
manilerms collected from a clam-fouled steam 
condenser of an electrical generator and proposes 
a possible design solution to the problem of foul- 
ing by the shells of this species. 


On 12 January, 1976, whole specimens and 
whole and half shells of Corbieida manilensis 
were collected from the clam-fouled steam con- 
denser of the Number Two electrical generator of 
the Handley Steam-Electric Generating Plant, 
maintained by the Texas Electric Service Com- 
pany on Lake Arlington, Texas (USGS map 
quadrangle, Arlington, 32° 43' 15" N: 97° 12' 57" 
W). This plant utilizes raw lake water as a 
coolant for the steam condensers of its three 
generating units. The maximum flow of lake 
water through the condensers is 1.298X10* liters 
per minute (1.870X10' 1/day) and the monthly 
average discharge rate is 1.052X10* 1/per minute 
(1.514X10' 1/day (Hall, 1972; McMahon. 1975). 
The clams were collected from three areas in the 
steam condenser: the inlet or cold water box 
(CWB) which receives raw lake water for cooling 
from the intake canal; the condenser tubes (CT) 
which carry water from the CWB and which are 
used to cool and condense the steam passed over 
them before it is returned to the generator's 
boilers: and the outlet or warm water box 
(WWB) which receives warmed water from the 
condenser tubes. Water is passed from the WWB 
to the discharge canal and is then returned to the 
lake (for a more complete description of the 
Handley Power Plant's operation see McMahon, 

The condenser tubes of the Number Two 
gererator have an outside diameter of 22.2 mm, 
an inside diameter of 19.7 mm and a tube wall 
thickness of 1.24 mm. The Number Two generator 
is a "peaking" unit which operates only during 

periods of high demand. It has an output of 80 
MW and a maximum flow through its condenser 
of 132,469 1/min. Average water velocity in the 
intake tube to the condenser is 2.44 m/min and 
velocity increases to 2.26 m/sec in the condenser 

C. manilenda was first observed in Lake Ar- 
lington during the spring of 1973 (John Barnett, 
personal communication) and it first fouled the 
Number Two condenser at the Handley Power 
Plant in the summer of 1974. Since that time the 
Number Two unit has been shut down several 
times in order to remove C. manilensis shells 
from its condenser tubes. Such fouling has never 
occurred in the larger Number Three unit, a con- 
tinuously running "base load" generator, with an 
output of 400 MW and a water flow through its 
condensers of 435,322 1/min. This unit's water 
velocities are similar to that of the Number Two 
unit, but the condenser tubes are larger with an 
outside diameter of 25.4 mm, an inside diameter 
of 22.9 mm and a tube wall thickness of 1.24 mm. 

Living specimens and empty whole and half 
shells of C. manilensis were collected from the 
Number Two condenser 72 hours after the 
generator had been shut down on January 9, 
1976. Samples were randomly removed from each 
of three areas (CWB, CT and WWB) and re- 
turned to the laboratory. For each individual in 
each sample three shell dimensions were meas- 
ured to the nearest 0.05 mm using a dial microm- 
eter. The shell dimensions recorded were: shell 
length (SL), the greatest dimension anterior- 
posterior across the shell; shell height (SH) the 
greatest dimension dorsal -ventral across the shell 
from the umbones to the ventral edge of the 
valves: and shell width (SW), the greatest lateral 
dimension between the two valves (for single 
valves shell width was estimated by multiplying 
the greatest lateral dimension by two). No sig- 
nificant differences occurred in the mean dimen- 
sions of whole and half shells in each sample (P 
> 0.10); therefore, the dimensions of whole shells 
and single valves were combined, allowing the 
computation of a mean SL, SH and SW with cor- 
responding standard deviations for each of the 
three samples (CWB, CT. WWB). The distribu- 
tions of sample shell dimensions from all three 


April 25,1977 

Vol. 91 (2) 

collection sites were then compared for sig- 
nificance using students' t test. 


Figures one, two and three illustrate the shell 
size distributions of C. nunulrnsis collected from 
the cold water box (CWB) (Fig. 1), the condenser 
tubes (CT) (Fig. 2) and the warm water b)X 
(WWB) (Fig. 3) of the Number Two steam con- 
denser. Approximately 20-30% of the shells 
removed from each of the three portions of the 
condenser contained intact soft parts. There was 
no evidence of byssal attachment by the clams to 
tube walls or any other portion of the condenser 
as has been previously suggested for fouling by 
this species (Sinclair and Isom, 1961, 1963). 

The 122 shells collected from the intake or cold 
water box (CWB) had a mean SL of 21.1 mm (s.d. 
= ±6.19 mm, range = 5.7 - 33.(S mmj.a mean SH 
of 19.98 mm (s.d. = ±5.29 mm, range = 4.9 - 28.1 

— I r 


10 15 20 25 


FIG. 1. Lfiujth frequency distrihutiona of Corbiciihi 
niiinilensis sheik collected from the inlet or cold water box 
(CWB), condenser tubex (CT) and outlet or warm ivater box 
(WWB) of a steam condenser utilmng raw lake water as a 
roolivit. The vertical axis is per cent of total sample mimhers 
and the hwizontal axis is shell length (SL) in millimeters. 
The darkened circles represent mean shell lengths for each 
s<tmple and bars aboid the means, .itandard deirialions. Tlie 
.■itipled vertical line represents the inside diameter (19.7 mm) 
of the condenser tubes. 

1 r 

10 15 20 25 


FKi. 2. Height freqnencii distributions of C. nianilensis 
■fhells collected from the inlft or cold unter btix (CWB), con- 
denser tubes ((JT) and outlet or warm box (WWB) of a steam 
coiuietiser utilizing raw lake water as a coolant. The vertical 
axis is per cent of total sample numbers and the horizontal 
axis is shell height (SH) in millimeters. The darkened circles 
represent mean shell heights for ench somplc and the liars 
about the means, statutard deiiations. The stipled vertical line 
represents the inside diamenter (19.7 mm) of the condenser 

mm) and a mean SW of 12.37 mm (s.d. = ±3.48 
mm, range = 3.8 - 20.0 mm). Corresponding 
mean shell dimensions for the 51 shells removed 
directly from the condenser tubes were: mean SL 
= 24.4 mm (s.d. = ±4.17 mm, range = 10.6 - 
32.0 mm); mean SH = 20.95 mm (s.d. = ±3.74 
mm, range = 8.2 - 27.8 mm); and SW = 14.22 
mm (s.d. = ±2.41 mm, range = 6.1 - 18.8 mm) 
(Fig. 2). Mean dimensions for the sample of 150 
shells drawn from the warm water box (WWB) 
were: mean SL = 16.72 mm (s.d. = ±3.75 mm, 
range = 4.6 - 23.1 mm); mean SH = 14.28 mm 
(s.d. = ±3.75 mm, range = 3.4 - 19.7 mm); and 
mean SW = 9.89 mm (s.d. = ±2.17 mm, range 
= 2.7 - 13.6 mm) (Fig. 3). The shell sjimples 
drawn from all three regions of the condenser 
(CWB, CT. WWB) were significantly different 
from each other (P <(U)5) in all three dimen- 
sions measured (SL, SH, SW). 

Vol. 91 (2) 

April 25, 1977 



Since 1960 there have been a series of reports 
recording the fouling of water-cooled steam con- 
densers by C. manilensds in both steam-electric 
power plants and other industrial facilities 
(Ingram, 1959; Sinclair and Isom, 1960, 1963; 
Sinclair, 1963, 1964, Thomas and MacKenthun, 
1964; Thomerson and Myer, 1970, Diaz, 1974). 
Several of these reports suggest that C. manilen- 
ds attach as young by a byssus to the walls and 
insides of tubes carrying cooling water in the 
condensers (Sinclair, 1963, 1964; Sinclair and 
Isom, 1960, 1961). Unlike these previous reports 
no small clams (SL < 5 mm) and no evidence of 
byssal attachment could be observed in any part 
of the Handley Power Plant's Number Two con- 
denser even though living clams with intact soft 
parts represented a significant proportion of all 
three samples. 

A comparison of the size distributions of the 
three samples indicates that the clams fouling the 
condenser are not a resident population, but in- 
stead, must have been carried into it from an ex- 
ternal population. The distribution of SL in the 
CWB had a mean of 21.1 mm. (s.d. = ±6.19 mm) 
(Fig. 1) which was significantly different (P < 
0.05) from the distributions of SL of both the CT 
and WWB. The distribution of SH in the sample 
of C. manilensis shells dravm from the condenser 
tubes was significantly different from both the 
samples taken from the CWB and WWB (Figs. 1, 
2 and 3) and had a mean SH of 20.95 mm and a 
rather narrow distribution of shell height about 
the mean (s.d. = ±3.74 mm) (Fig. 2). The inside 
diameter of the Number Two unit's condenser 
tubes at 19.7 mm is almost equal to the mean SH 
(20.95 mm) of the shells sampled from them. As 
shell height (SH) approximately represents the 
smallest diameter across the plane between the 
two valves, these data appear to indicate that C. 
manilensis shells are transported into the con- 
denser tubes and only those of an appropriate 
size (i.e., an SH closely approximating the inside 
diameter of the tube) would become lodged in the 
tubes at points of slight constriction (primarily at 
regular bends in the condenser tubing). The few 
smaller shells (SH < 17 mm) found in the con- 
denser tubes were taken from tubes already oc- 


FIG. .3. Width frequency distributions of C. manilensis 
shells collected from the inlet or cold water box (CWB). con- 
denser tubes (CT) and outlet or warm water box (WWB) of a 
steam condenser utilizing raw lake water as a coolant. The 
vertical axis is per cent of total sample numbers and the 
horizontal axis is shell width (SW) in millimeters. The 
darkened circles represent mean shell widths for each sample 
and the bais about the means, standard demations. The 
stipled vertical line represents the inside diameter (19.7 mm) 
of the condenser tubes. 

eluded with larger wedged shells which prevented 
their passage. In the outlet or warm water box 
(WWB) only shells with a SH less than the inside 
diameter of the condenser tubes (SH < 19.7 mm) 
were taken (Fig. 3), the sample from this area 
having significantly smaller shell dimensions (P< 
0.05) than the samples from both the CWB and 
CT. Thus, it appears that the shells in the WWB 
must be carried from the CWB through the con- 
denser tubes to the WWB and that only clams 
with an SH smaller than the inside diameter of 
the condenser tubes may pass through them. In- 
gram (1959) has reported a similar accumulation 
of C. manilensis shells in tubes with an inside 
diameter of 15.8 mm from a condenser in Califor- 

In this sense the condenser acts as a sieve. 
Clams are drawn into the CWB from an external 
population with intake currents and therefore 


April 25.1977 

Vol. 91 (2) 

shell size distributions in this are are represent- 
ative of those in natural Lake Arlington popula- 
tions of C. manilensis (Aldridge, 1976). Of those 
shells drawn into the CWB those with SH's of 
less than the inside diameter of the condenser 
tubes eventually pass through the condenser to 
the discharge canal leaving the largest shells in 
the CWB. The condenser tubes themselves become 
initially fouled only with those shells with a SH 
approximately their inside diameter. These shells 
apparently become lodged at slight constrictions 
in the tubes or at bends in the tubes. Water 
velocities in the condenser tubes at 2.26 m/sec 
are probably much too great to allow veliger set- 
tlement and therefore shells must be transported 
into this portion of the condenser. 

Relatively dense populations of C. manilensis 
occur both in the intake canal of the power plant 
and in the shallow shore areas of Lake Arlington 
(Aldridge, 1976). Throughout the year living 
specimens of C. manilensis in Lake Arlington 
have been observed to move entirely out of the 
substrate and be carried over the bottom by cur- 
rents and wave action. Similar observations have 
been made for a C. manUensis population on the 
James River, Virginia (R. J. Diaz, personal com- 
munication). C. manilensis may move out of the 
substrate when environmentally stressed and be 
carried by currents in the pwwer plant's intake 
canal to traveling screens in front of the intake 
tunnels to the condensers. The traveling screens 
of the Handley Power Plant on Lake Arlington 
have a mesh size of 12.7 mm which prevents 
clams large enough to foul the condensers from 
entering the intake tunnels. However, smaller 
clams with an SH less than 12.7 mm, spat and 
veligers will pass easily over the screens. If these 
clams settle in the embayments behind the 
screens or in the intake tunnels where water cur- 
rents are relatively slow (2.44 m/min) they will 
grow very rapidly and reach an SH large enough 
to allow them to lodge in condenser tubes (ap- 
proximately 19 mm) in two to six months (Al- 
dridge, 1976). Thereafter, if the quality of lake 
water drawn into the intake canal is lowered by 
natural means (i.e., high summer temperatures or 
low oxygen concentration) or as the result of 
human activity (shock chlorination and other per- 

turbations) the now resident Corbicida popula- 
tions behind the screens may move out of bottom 
slits to be carried by intake currents into the 
condensers. Such populations of adult C. manilen- 
sis have been observed behind the traveling 
screens at the Handley Power Plant on Lake Ar- 
lington (M. W. Zengerle, personal communica- 

It has been reported that adult C. manilensis 
are not susceptible to shock chlorination as a 
method of control (Sinclair and Isom, 1960, 1961; 
Sinclair, 1963, 1964); instead, constant chloration 
of intake waters at levels of 1.5-10 ppm (up to 50 
ppm for two weeks) have been recommended as a 
means of preventing this species from impinging 
upon condensers (Sinclair and Isom, 1960, 1963; 
Sinclair, 1963, 1964). Present Environmental Pro- 
tection Agency regulations generally prohibit 
constant chlorination of raw intake water used 
for cooling purposes and shock chlorination may 
actually enhance condenser fouling by stressing 
resident populations. 

It is notable that the larger Number Three 
generating unit at the Handley Power Plant on 
Lake Arlington has never had its steam con- 
densers fouled with C. manilensis. The only 
discemable difference in the operation of its con- 
densers and those of the often-fouled Number 
Two unit is that the inside diameter of its con- 
denser tubes is larger at 22.9 mm (see Methods). 
As such it would only stop clams with an SH 
greater than 22 mm which represents only about 
1.51% (s.d. = ±2.22%, range - 8.9%, N = 28) of 
the normal Lake Arlington C. manilensis popula- 
tion over 1975 while the Number Two unit's con- 
denser tubes have a smaller inside diameter (19.7 
mm) and would stop about thirteen times as 
many clams (19.45%, s.d. = ±13.41%, range = 
3.7 - 64.4%, N = 28) (Aldridge, 1976). Since so 
few clams of the appropriate size for fouling im- 
pinge upon this larger unit's steam condenser (in- 
side diameter 22.9 mm), it is hypothesized that 
the high water velocities in its condenser tubes 
abrade and break up lodged shells at a rate 
which prevents serious fouling. In contrast, a far 
greater number of appropriately sized shells im- 
pinge on the smaller tubes of the Number Two 
unit's condenser (inside diameter = 19.7 mm) 

Vol. 91 (2) 

April 25, 1977 


allowing a steady accumulation of lodged shells 
in the condenser tubes, eventually impairing the 
condenser's efficiency. 

It may be possible to avoid Corbindn fouling in 
water-cooled steam condensers of future electrical 
generating and industrial facilities by designing 
steam condensers with condenser tubes of inside 
diameters greater than 29.0 mm, the approximate 
SH of a specimen of C. manUends 50 mm in shell 
length (Aldridge, 1976). A specimen of this shell 
length (50 mm) was the largest ever taken in over 
a year of bi-weekly collections of ('. mariilcusix 
on Lake Arlington (Aldridge, 1976) and is 
roughly equal to or less than the maximum shell 
lengths reported for other populations of this 
species near fouled condensers (Sinclair and Isom, 
1961, 1963; Sinclair, 1963, 1964; Thomas and 
MacKenthun, 1964; Thomerson and Meyer, 1970; 
Diaz, 1974). Therefore, designing condensers 
which would allow passage of even relatively 
large specimens of C. manilensis (inside diameter 
of condenser tubes > 29.0 mm) might eliminate 
all possiblity oiCorbicula fouling. 


I wish to express my deep appreciation to Mon- 
ta Zengerle, Texas Electric Service Company 
Biologist, who allowed me to be present when the 
condenser was inspected and who supplied data 
on the steam condenser's operation; to David W. 
Aldridge for his advice and discussions on the 
biology of C. manilensds; and to Nancy B. Banks, 
for her assistance with the preparation of the 


Aldridge, D. W. 1976. Growth, reproduction and bioener- 
getics in a natural population of the Asiatic freshwater 

clam, (hrbinda manilen.tis Philippi. Maiytfr'n Thexis. TTie 
University of Texas at Arlington. 93 pp. 

Diaz. R. J. 1974. Asiatic clam, Girhinda manUends (Philippi). 
in the Tidal James River, Virginia. Chesapeake Si-i. 15: 

Hall. F. M., III. 1972. Species diversity and density of the ben- 
thic macroinvertebrates inhabiting a reservoir receiving a 
heated effluent. Master's The^s. The University of Texas at 
Arlington. 82 pp. 

Ingram, W. M. 19.59. Asiatic clams as potential pests in 
California water supplies. Jour. Amer. Water Works Assoc. 
51: 36.3-.369. 

McMahon. R. F. 1975. Effects of artificially elevated water 
temperatures on the growth, reproduction and life cycle of 
a natural population of Physa iri.rgata Gould. Ecology 56: 

Prokopovich, N. P. 1969. Deposition of clastic sediments by 
dam&.JmrSed. Petrology 39: 891-901. 

Prokopovich, N. P. and D. J. Hebert. 1965. Sedimentation in 
the Delta-Mendota Canal. Jour. Amer. Water Works Assoc. 
57: 375-382. 

Sinclair, R. M. 1963. Kfects of an introduced clam (Corbicula) 
on water quality in the Tennessee River Valley. In Pro- 
ceedings of the Second Indiistnal Waste Conference. 
Vanderbilt University. Tennessee Department of Public 
Health. Tennessee Stream Pollution Control 3oard. pp. 

Sinclair, R. M. 1964. Clam pests in Tennessee water supplies. 
Jour. Amer. Water Works Assoc. 56: 592-599. 

Sinclair, R. M. 1971. Annotated bibliography on the exotic 
bivalve Corbieida in North America, 1900-1971. Sterkiana 
40: 11-18. 

Sinclair. R. M. and B. G. Isom. 1%1. A preliminary report on 
the introduced Asiatic clam Corbiada in Tennessee. Ten- 
nessee Stream Pollution Control Board. Tennessee Depart- 
ment of Public Health. 31 pp. 

Sinclair. R. M. 1963. Further studies on the introduced 
Asiatic clam in Tennessee. Tennessee Stream Pollution Con- 
trol Board. Tennessee Department of Pulbic Health. 51 pp. 

Thomas. N. A. and K. M. MacKenthun. 1964. Asiatic clam in- 
festation at Charleston. West Virginia. The NautUus 78: 

TTiomerson, J. E. and D. G. Myer. 1970. Corbiada manilensis: 
Range extension upstream in the Mississippi River. 
Sterkiana 37: 29. 


April 25,1977 

Vol. 91 (2) 


M. G. Harasewych 

College of Marine Studies 

University of Delaware 

Newark, Delaware 19711 


A specimen of Littorina lineolata Orbigny from Oistint^ Bay. Barbados was 
found to have a normal orthostrophic protoconch and an abnormal. 
hypertrophic teleoconch. based on examination of anatomy, shell, protoconch 
and (rperculum. This is believed to be the first report of such an abnormality in 

The occurrence of anomalous shell mor- 
phologies is well documented in the Littorinidae 
of tropical as well as boreal waters (Rosewater, 
1972). It was therefore not too surprising to 
discover what appreared to be a sinistral 
specimen of Littorina lineolata Orbigny. 1840 
while sorting material collected in Oistins Bay, 
Barbados. Closer examination, however, revealed 
this specimen to be dextral and hyperstrophic. 

It is necessary at this point to make a distinc- 
tion between asymmetry of the shell and asym- 
metry of the soft parts. The terms dextral and 
sinistral, in the strict sense, refer to the orienta- 
tion of organ systems in the gastropod body. The 
vast majority of prosobranchs are dextral and 
have lost the osphradium, ctenidium, hypobran- 
chial gland and auricle on the post -torsional right 
side of their body. This was accompanied by a 
shifting of the anus to the right side of the body 
and modification of the right kidney into a 
reproductive organ. The reverse is true of 
sinistral gastropods, which are mirror images of 
their dextral counterparts. Dextrality or 
sinistrality is detectable as early in development 
as the late two cell stage (Crampton, 1894), long 
before even the first appearance of a shell. 

The terms orthostrophy and hyperstrophy refer 
to the orientation of the asymmetrical shell with 
regard to the soft parts. The term orthostrophic is 
applied to gastropods in which the spire is on the 
same side of the body as the anus and pallial 
reproductive organs, while the term hyper- 
strophic is applied to gastropods in which the 

spire is on the same side of the body as the un- 
paired osphradium, ctenidium, hypobranchial 
gland and auricle. Tlie direction of coiling is 
determined in the larval stage, but, in some gas- 
tropods, is changed at the time of metamorphosis 
(e.g. Architectonicidae, Pyramidellidae). 

Robertson and Merrill (196;3) reported the ab- 
normal occurrence of post -larval hyperstrophy in 
two species of Heliarus. in which the normal 
hyperstrophy of the protoconch was abnormally 
retained by the teleoconch. The specimen of Ldt- 
torina lineolata discussed here, however, is be- 
lieved to be the first reported occurrence of a gas- 
tropod with a normal orthostrophic protoconch 
and an abnormal hyperstrophic teleoconch. This 
specimen (figure 1), in the collection of the 
Academy of Natural Sciences of Philadelphia 
(ANSP no. 342287), was compared to normal 
specimens from the same locality (ANSP no. 
342286) and proven to be dextral and hyper- 
strophic on the basis of the following evidence. 

Anatomy. Tissue as far up as the rear of the 
mantle cavity was well preserved. The orientation 
of the mantle cavity organs was that of a de.xtral 
animal, the anus and capsule gland being on the 
right side of the body, while the osphradium, 
ctenidium and hypobranchial gland were on the 

Operculum. As demonstrated by Pelseneer 
(1893, fide Robertson and Merrill, 1963), the 
direction of coiling of the operculum can be used 
to distinguish between dextral and sinistral 
animals, the former producing opercula which 

Vol. 91 (2) 

April 25, 1977 


FIG. 1. .4, luirmiil apecunen nf Littorina lineolata Orbigny 
fmm Oistins Bay. Barbados. x2. B. Hifperstrophic specimen 
from the .same locality. xS. 

coil counter-clockwise when viewed externally, 
and latter produce opercula which coil in the 
clockwise direction when viewed externally. The 
operculum of the specimen in question (figrure 2) 
is coiled in the counter-clock-wise direction, in- 
dicating that the animal which produced it was 

ProtoctDirh. As there is considerable pitting of 
the early whorls, it is not possible to locate the 
exact boundary between protoconch and 
teleoconch stages, but there is clearly a change in 
the direction of coiling of about 140 degrees bet- 
ween the axis of the early whorls of the pro- 
toconch and the axis of the adult shell (figure 3), 
indicating that the specimen was initially dextral 

FIG. 2. Ertenial mew of operadum of the hifperstrophic 
Littorina lineolata. xlO. 

FIG. 3. Early whorls of the hifperstrophic Littorina lin«)- 
lata. xl2. 

and orthostrophic but became abnormally 
hyperstrophic near the time of metamorphosis. 

Shell. There are two major shell characters 
which attest to the hyperstrophy of this 
specimen: the location of the major spiral cords 
relative to the shoulder, and the direction of the 
brown axial bands relative to the columella. Nor- 
mal specimens are characterized by having 11 or 
12 major spiral cords on the apical side of the 
shoulder and a variable number of very fine 
spiral threads on the adapical side of the 
shoulder. This situation is reversed in the 
hyperstrophic specimen, the fine spiral threads 
being located on the apical side, while 11 major 
spiral cords are located on the adaptical side of 
the shoulder. When viewing the orientation of 
the brown axial lines relative to the columella, it 
can be seen that in normal individuals the brown 
bands approach the columella tangentially, while 
in the hyperstrophic specimen the bands appear 
to be almost perpendicular to the columella. 

It should be noted that the actual shape of the 
aperture relative to the animal is not very 
drastically changed, the left side being more 
spacious than the right. This would have de- 
creased the compression of the ctenidium, which 
would have been a serious impediment to the sur- 
vival of the organism. 

I thank Dr. Robert Robertson (Academy of 
Natural Sciences of Philadelphia) for reviewing 
the manuscript. 


April 25.1977 

Vol. 91 (2) 


Crampton, HE. 1894. Reversal of Qeavage in a Sinistral 
Gastropod. Annals N. Y. Aaui. Sci 8: 167-170. pi. .5. 

Pelseneer. P. 1893. A propos de 1' "Asymetrie des Mollusques 
univalves." Jtmrn. Qmchyliologie iO: 229-23.3, 1 fig. 

Robertson. R. & Merrill, A.S. 196:?. Abnormal Dextral 
Hj^perstrophy of Post-Larval Heliacius (Gastropoda: Ar- 
chitectonicidae). The VeliyerG: 76-79, pi. 13-14. 

Rosewater, J. 1972. Teratologicai Littorina scabra angulifera. 
The Nautilus 86: 70-71. 6 fig. 


Leroy H. Poorman and Forrest L. Poorman 

Los Angeles County Museum of Natural History 
Los Angeles, California 90007 


Field notes on Lobiger souverbii, Oxynoe panamensis, Berthelina chloris, 
and Phyllaplysia padina, nil from HV,s-/ Mexico, are munmarized. 77n'.s' inrlndetf 
descn{jtion,s of the living animals and obseirations on their habits and habitats. 
Range extensdons northwaM into the Gulf of California are recorded for the 
first three species. Geographical rongcs in the Tropical Eastern Pacific arc 
<] ircn for all four species. 

The last several years have presented op- 
portunities for intensive collecting and observa- 
tion of Panamic opisthobranchs. Collecting sta- 
tions ranged from Cabo Tepoca. Sonora, to Man- 
zanillo. Colima. Mexico. Several stations on the 
east coast of Baja California at Bahia de Concep- 
cion and Bahia de Los Angeles were visited. 
Opisthobranchs were observed and photographed 
in the field and in aquaria. Numerous species 
were preserved and are on deposit at the Natural 
History Museum, Los Angeles County, California. 
Copies of 35 mm slides are also on deposit. 

A review of our field notes reveals some in- 
teresting information on four of the opistho- 
branchs living on marine algae. We believe that 
these notes and comments will be of some in- 
terest and will stimulate further field observa- 

Lobiger souverbii Fischer, 1857 

On February 17, 1974, during^ a series of low 
tides, we were collecting at Bahia de Tenacatita, 
Jalisco. On Caulerpa racemosa var. turbinata 

(type 1), which resembles bunches of tiny grapes 
(Keen & Smith. 1961), we found 25 specimens of 
Lobiger souverbii Fischer, 1857. Several were 
crawling over the surface of the Caidoim: but 
most were in nests along the lower edge of the 
algae, usually adjacent to sand. Sometimes, as 
many as five animals were in the same nest. A 
number of specimens were kept alive in an 
aquarium for several days for observation and 
photographing. The living animal is well-figured 
in Keen. 1971. 

Lobiger souverbii has four parapodia which are 
lateral extensions of the foot and are not to be 
confused with cerata which are dorsal appen- 
dages containing diverticula associated with 
digestion. The parapodia are extensions of the 
foot below the four corners of the shell and curl 
upward. The branches are like long narrow leaves 
with ruffled edges. They are a lighter green than 
is the body, which is the green of the algae. On 
approximately half of the animals observed, there 
was an orange band on the upper side of each 
branch, inset slightly from the margin. The 

Vol. 91 

April 25, 1977 


parapodia were normally extended upward at an 
angle of 45° and were partially rolled inward. 
When disturbed, the animals flexed and recurled 
these in a rapid cyclic sequence. When oxygen 
was depleted, the animals became lethargic and 
the parapodia were completely extended horizon- 

The caplike shell is on the dorsum, exactly 
between the four branches of the parapodia. Mot- 
tled green of the internal organs and a strong 
blue veining shows through. When removed from 
the animal, the shell is clear but became translu- 
cent when dry. 

While the animals were in the tank, auto- 
tomizing of the parapodia was observed. Several 
individuals had previously discarded one or more 
of the lobes. No instance of regeneration was ob- 

This species appears to be very social. Not only 
did several animals share a common nest, but 
when 25 specimens were placed in an acquarium, 
they at once formed a close group. Within min- 
utes, sexual activity was observed, involving two 
or more individuals at the same time. Within 
hours, the algae was covered with gelatinous 
strings containing thousands of microscopic, 
spherical yellow eggs. 

In December, 1975, we found one specimen of 
Lobiger sourerbii sharing a common nest with 
two other opisthobranchs. They were on a dif- 
ferent type of Caiderpa (type 3) at Bahia de 
Algodones, Guaymas Area, Sonora. This is a 
northward range extension for the species. The 
known range is now from Bahia de Algodones, 
Sonora, to Bahfa de Tenacatita, Jalisco, on the 
mainland of Mexico. It is also recorded from Cabo 
San Lucas, Baja California Sur (Larson & Bertsch, 
1974) and from the Galapagos Islands, Ecuador 
(Sphon & MuUiner, 1972). 

Oxynoe panamensis Pilsbry & Olsson, 1943 

A single specimen of Oxynoe panamensis 
Pilsbry & Olsson, 1943, was found on the Caider- 
pa at Bahia de Tenacatita. Like Lobiger. it had 
the ability to cling to the algae by suction of the 
foot. When attempts were made to remove the 
animal from the algae, a greenish white mucus 
was excreted from glands along the side of the 

foot. This mucus seemed to have adherent proper- 
ties for the animal. It is more probable that the 
mucus served as a defense mechanism (Sphon & 
Mulliner, 1974). 

Oxynoe panamensis was described from a 
single shell in the beach drift on Isla Bocas, Golfo 
de Panama (7° 30' N, 80° 37' W). The living 
animal is figured in Keen, 1971. The body is long, 
slender, and slightly humped (30 x 4 x 4 mm). 
The first one-fourth of the body is made up of the 
head and neck. The second one-fourth comprises 
the shell, most internal organs, and two para- 
podia, one on each side. The posterior one-half of 
the body is the tail. The head is small and blunt 
with relatively large, nonretractable, inrolled 
rhinophores projecting horizontally from the lat- 
eral extremities. The angle between the rhino- 
phores is 90-120°. The mouth is on the underside 
of the head and is preceded by two rounded lips. 

The short neck extends back to the rounded 
anterior end of the shell. This is broad and cap- 
like on the dorsum and contains most of the vital 
organs. Behind the shell, the body tapers narrow- 
ly into a sharp tail. There is a ridge extending 
from just behind the shell along the back to the 
posterior extremity. 

Tine foot is extended laterally into two para- 
podia which rise upward over the shell to meet 
dorsally. Normally, the shell is completely 
covered except for the forward edge. The para- 
podia extend around the shell to the rear but do 
not quite meet until about 1 mm behind, where 
they fuse to form the ridge down the back. Ex- 
cept for the head, the body and parapodia are 
sparsely covered with sharp papillae. 

Overall color of the animal is the green of the 
algae. The papillae are white and there are small 
white dots over the entire animal, most numerous 
along the lower edge of the foot and toward the 
extremities of the rhinophores. Black spots alter- 
nate with white dots along the foot margin and 
are scattered with white on the upper one-half of 
the rhinophores. Blunt papillae and white spots 
are concentrated along the posterior dorsal ridge. 

When the parapodia are removed, the internal 
organs are revealed through the transparent 
shell. The organs are varying shades of green and 
clearly show a pattern of white dots. 


April 25,1977 

Vol. 91 

In November, 1974, 32 specimens of Orjfnoe 
panmnptifns from 4 to 30 mm in length were col- 
lected from a feathery form of Caulerpa (type 2) 
at Tinajas, Bahia de Bachwibampo, Sonora. This 
algae resembled Calerpa racemosa var. ser- 
tularioides reported by Keen & Smith, 1961, from 
Lsla Flsp'ritu Santo. One year later, the algae in 
the same region had greatly diminished in quan- 
tity and deteriorated in quality and only a few 
animals were found. 

The collected animals were kept in an aerated 
aquarium for six weeks. Fresh algae was pro- 
vided at intervals. The animals moved about free- 
ly on the algae and tank walls, exhibiting the 
same social habits as Lobiger except for the flex- 
ing of the parapodia. This species seems to be less 
e.xcitable than Lobiger. When placed in the tank, 
the animals began sexual activity at once. Soon, 
the glass walls showed numerous spirally coiled 
egg masses containing microscopic, spherical 
yellow eggs. Actual laying of the eggs was ob- 
served and photographed through the glass as the 
egg mass was deposited. One animal moved along 
an irregular path with the gelatinous ribbon ap- 
pearing from the broad front of the foot to be 
deposited on the glass. Two other animals 
crowded close on the right side and just behind 
the head of the animal that was depositing the 
egg mass. 

We further noted that Lobiger souverbii from 
the southern part of the range was abundant, 
with the animals large, brightly colored, and 
vigorous; but that the specimen from Bahia de 
Algodones was in poor condition. In contrast to 
this, ()xi/)io(' paudmcnsis was abundant at 
Guaymas. The animals were in fine condition 
compared to the single pale specimen from Bahia 
de Tenacatita. 

Autotomizing of the parapodia, which is not 
uncommon with Lobiger. was not observed with 
OxifHoe. However, the latter have been reported 
able to autotomize the tail section. The actual act 
was not observed in our tank; but several tail 
sections were found on the bottom of the tixnk 
and several animals without tails were observed. 
When dropped into alcohol, almost all of the 
animals seperated the tail se.lion from the body 
at a point just behind the parapodia and the 

The recorded range for Oxijnoe panamensis is 
at lsla Espiritu Santo, Gulf of California, (Keen, 
1971). and from the Guaymas area, Sonora. Mex- 
ico, to Golfo de Panama (type locality). 

BertheIiniachloris(DaIl, 1918) 

We were collecting at the south end of Bahi'a 
de Algodones on November 29, 1975. At low 
water, we were out on the reef, which is 2 or 3 
acres in extent. The tangled mass of Caulerpa 
(type 3) was encountered for the first time. We 
picked up a small rock with a clump of the algae 
attached, thinking to e.xamine the holdfast where 
we had previously found Sulcoretusa. Nestling 
among the branches was what seemed to be a 
small green bivalve. When the specimen was 
removed to a vial of sea water, a small green 
slug-like body emerged and began to crawl about. 
There were two valves inverted on its back with 
what appeared to be the hinge oriented upward 
and to the rear. Four small clumps of the algae 
yielded 13 specimens. We knew that we had 
found our first Betihelinia chloris (Dall, 1918). 
This is a range extension northward from lsla 
Espiritu Santo (Keen, 1971). The known range is 
now Abreojos to La Paz, Baja California Sur. 
Keen. 1971, states that the species possibly occurs 
at Guaymas. This is now confirmed. The species 
has also been reported from the Galapagos 
Islands. Ecuador (Sphon & Mulliner. 1972). The 
living animal was illustrated in Sphon & Bertsch, 

When collected, all of the animals were 
withdrawn and with the shells closed. One nest in 
a cavity in the algae yielded eight specimens. 
Several very small individuals were in this nest 
and would have been overlooked except that they 
were clinging to the shells of the adults. As the 
animals were removed, they were found to be at- 
tached to the algae with the fine elastic threads 
which have been previously reported (Sphon & 
Mulliner, 1972). Betihelinia were subsequently 
observed to produce large amounts of mucus from 
glands along the posterior foot margin. TTie 
mucus soon sets, in the salt water, into elastic 
threads which the animal spins. 

When first placed in the aquarium, the ani- 
mals clung together in a tight ball. As they slow- 
ly dispersed, the young ones continued to cling to 

Vol. 91 (2) 

April 25, 1977 


the shells of the larger ones. Sexual activity was 
not observed. The presence of so many juveniles 
in November may indicate that reproduction is 
seasonal and occurs in late summer. 

The largest specimen had a shell 9.5 mm long. 
When placed in sea water, the valves parted 
slightly and the narrow slug-like body appeared, 
oriented so that the shell would be supported by 
the branches of the algae. On the bottom, the 
animal could support the weight of the shell in 
an upright position for only a few seconds before 
it would fall to one side. The animal moved with 
an alternating motion between the front part and 
the back part of the foot. The animals in the tank 
tended to crawl up the sides to the surface where 
they would form a cup with the bottom of the 
foot and use surface tension to float upside dovm 
with the heavy shell hanging down. 

Most of the internal organs appeared to be in- 
side the heavy shell and gave it a mottled green 
color. The shell opened only about 1' 2 mm as the 
small green body extended in front about 4 mm 
and the tail showed only slightly behind. The 
body was about 2 mm in height and less in 
width. On the front of the head were two rolled, 
yellow-tipped rhinophores which were about 2 
mm in length. The forepart of the foot was slight- 
ly extended and widened. Just above the exten- 
sion of the foot was a flangelike lip. Behind the 
rhinophores on top of the neck was a small tur- 
retlike hump with two eye spots on the front. A 
slight ridge extended from this hump along the 
neck and into the shell. Under 20 magnifications, 
the body was clear and gelatinous, with horizon- 
tal rows of microscopic green nodules as inclu- 
sions. There was a row of small white dots along 
the margin of the foot and on the rhinophores. 

When the animal withdrew, a sequence of 
events took place. The foot folded downward 
along a central line, the rounded cheeks folded 
inward, the rhinophores came together vertically, 
and the body disappeared into the shell which 
then closed. 

The shell was translucent yellow-green with 
several clear rays extending from the umbones to 
the margins. Two dark rays were on either side 
of each umbone and extended laterally for about 
1 mm. The tightly coiled nucleus of the em- 
bryonic shell was attached to the umbone of the 

left valve and extended horizontally across the 
umbone of the right valve. 

Phyllaplysia padina Williams & Gosliner, 1973 

In March, 1975, a number of specimens of 
Phyllaplysia padina Williams & Gosliner, 1973 
were collected from Padina in tide pools at Cabo 
Tepoca, Sonora. The animals were observed, 
photographed, and preserved. Several shells were 
extracted and photographed. Excellent drawings 
of the animal have been published (Williams & 
Gosliner, 1973a); but the living animal has not 
been figured. 

Numerous specimens have since been taken 
from Padina intertidally in the Guaymas Area as 
far north as Bah'a de Algodones. In May, 1975, 
and again in May, 1976, large numbers of these 
animals were observed at Bahi'a de Los Angeles, 
Baja California Norte. On Isla Smith in this 
region, there is a man-made turtle pond. When 
the tide is out, water pours over a six foot dam 
into a pool. There is some Padina in this pool. In 

1975, six Phyllaplysia padina were taken from 
here but there were no animals found in 1976. At 
Punta la Gringa, across the channel on the 
mainland, the species was abundant on the algae 
from low water out to at least 10 meters. In May, 

1976, high wind and rough water left large 
amounts of Padina at the high tide line. The 
algae was populated with this species. Twenty- 
four hours later, the algae was drying in the hot 
sun and wind. A few animals were still clinging 
to it and revived completely when placed in fresh 
sea water. 

We did observe a previously unrecorded fact 
concerning the coloring of the living animal. 
When studied under 20 magnifications, the body 
was uncolored and clear. The apparent greenish 
brown color was due to inclusion in the tissue of 
longitudinal rows of microscopic nodules. Several 
photographs show this so clearly that individual 
nodules can be distinguished. Individual animals 
differed widely in the concentration of the 

The normal habitat and range for this species 
seems to be wherever Padina will grow and from 
the head of the Gulf of California at least as far 
south as the Twenty-eight Parallel. 


April 25.1977 

Vol. 91 (2) 


TVie p;uidance of Mr. Gale Sphon, Curatorial 
Assistant, Natural History Museum of Los 
Angeles County, in the preparation of the 
manuscript is gratefully recognized. We also 
thank Dr. James McLean, Curator of Invertebrate 
Zoolog>', Natural History Museum of Los Angeles 
County, who read the manuscript and made 
helpful suggestions. 


I>dll, W. H. 1918. Description of new species of shells, chiefly 

from Magdalena Bay. Lower California. Pi-oc. Hiol. Soc 

Wiish tnijtwL 31: .5-8 (Feb. 27). 
Fisc-her. Paul. 18.57. Description d'especes nouvelles. Jour, de 

Co/ic/if//. 5(2): 273-77 (.Jan.). 
Keen, A. Myra. 1960. The riddle of the bivalved gastropod. 

ne Velujer 3(1): 28-.30 (.July 1). 
Keen, A. Myra. 1971. Sea sheik of tropical West Ameiica : 

marine mollusks from I5aja California to Peru. Stanford 

Univ. Press. Stanford. Calif, i-xiv-t-1066 pp.; ca. 4000 figs., 

22colorplts. (Sept. 1). 
Keen. A. Myra and Allyn Smith. 1961. West American species 

of the bivalved ga,stroix)d genus Berthelinia. Proc. Calif. 

Acad. Sci. 30(2): 47-66; figs. 1-33; 1 pit. (March 2f)). 
Larson, Mary and Hans Bertsch. 1974. Northward range ex- 
tensions for Lobiger souverbii (Opisthobranchia: 

Sacoglossa) in the Eastern Pacific. The Veliger 17(2): 225 

(Oct. 1). 
Pilsbry. H. A. and A. A. OLsson. 194.3. New marine mollu.sks 

from the west coast. Ue Nautibu, 56: 78-81, pit. 8 (Feb. 15). 
Smith, Allyn. 1961. Notes on the habitat of Berthelinia sp. 

nov. from the vicinity of I^ Paz, Baja California, Mexico. 

The Veliger 3(3): 81-82 (.Jan. 1). 
Sphon. Gale. 1971. New opisthobranch records for the Eastern 

Pacific. Tfie Veliger 13(4): .368-69 (Oct. 1). 
Sphon. Gale and Hans Bertsch. 1974. Green Dragons. Terra 

(Quarterly Mag. Nat. Hist. Mus. Ljs Angeles Co.. Calif.) 

12(3): 21-29; color illustrated (Winter). 
Sphon, Gale and David K. Mulliner. 1972. A preliminary list 

of known opLsthobranch from the Galapagos Islands w^llected 

by the Ameripagos expedition. The Veliger 15(2): 147-.52; 1 

map (Oct. 1). 
Williams. G. C. and T. M. Gosliner. 197.3a. A new species of 

anaspidean optisthobranch from the Gulf of California. Ihe 

VW(!/f;- 16(2): 216-.32 (April 1). 
Williams, G. C. and T. M. Gosliner. 1973b. I^nge extensions 

for sacoglossan opisthobranchs from the coasts of California 

and the Gulf of California. The Veliger 16(1): 112-16; 2 

maps (.July 1). 


Clement L. Counts, III 

Department of Biological Sciences 

Marshall University 
Huntington, West Virginia 25701 

Previous reports of the Miocene bivalve Cum- 
imjid DK'dialis Conrad, lS()(i have been almost en- 
tirely limited to North Carolina, Maryland and 
Virginia. Glenn (1904) reported C. mcdiali.^ from 
the Miocene of Maryland and cited localities for 
specimens taken from Virginia and North Caro- 
lina. Shimer and Shrock (1944) also reported (\ 
nicdialis from the Choptank Formation of 
Maryland and gave ranges of Maryland, Virginia, 
North Carolina and South Carolina without 
citing specific localities. Richards (1947) reported 
a specimen taken from a well, 18.3 m from the 

surface, dug at Edenton, Chowan County, North 
Carolina. This specimen was placed in the collec- 
tion of the Academy of Natural Sciences of 
Philadelphia (ANSP 16773) where the holotype 
and paratypes, from James River, Vii-ginia, also 
reside (ANSP 18839). The present note reports 
the second locality in South Carolina from which 
C. mi'diulit< has been taken. 

A right valve of C. medialift was found in 
sea-wrack at the high tide line at Crescent 
Beach, Horry County, South Carolina 18 

Vol. 91 (2) 

April 25, 1977 


August 1975. The shell was believed to be of re- 
cent origin and was sent to Dr. R. Tucker Ab- 
bott for confirmation. However, upon examina- 
tion by Dr. Abbott at the Delaware Museum of 
Natural History, it was properly identified as a 
fossil or subfossil and accessioned DMNH 
103141. It was suspected by Dr. Abbott that the 
shell may have washed up from a fossil outcrop 

A specimen from the Peedee River, just south 
of the new locality, was reported by Glenn 
(1904). This specimen was the only such find of 
C. medialis in South Carolina prior to the pre- 
sent report. 

Mr. Robert H. Schlutter (personal com- 
munication) has noted that the specimens 
reported by Glenn (1904) from Maryland are 
most probably not from Maryland but from 

Virginia. Thus, the possibility that C. medialis is 
a Maryland form is doubtful and its citation as a 
representative bivalve of Maryland dubious. 
This was pointed out by Glenn (1904) but later 
references to the species place it in Maryland 
without noting this possibility. 

The author wishes to thank Dr. R. Tucker 
Abbott and Mr. Robert H. Schlutter for their ad- 
vice and assistance. 


Glenn. L. C. 1904. Mollusca (Pelecypoda). Maryland Geol. 

Survey, Miocene. 274-401. 
Richards, H. G. 1947. Invertebrate fossils from deep wells 

along the Atlantic coastal plain. Jour. PaleontoL 21(1): 

Shimer. H. W., and R. R. Shrock. 1944. Index Fossils of 
North AmeHca. MIT Press (Cambridge, Mass.). ix + &37 


Tom M. Spight 

Woodward-Clyde Consultants 
3 Embarcadero Center, Suite 700 
San Francisco, California 94111 


Among rocky shore and oyster-reef muricaceans. all high latitude species 
hatch as young stiails, while all tropical species hatch as veiigers. In contrast, 
species from other habitats at all latitudes generally hatch metamorphosed 
Among prosobmnchs in general, more species of both hatching types are fonnd 
at low latitudes than at high latitudes and, m Europe, on continental suites 
rather than on islands. 

One of the most intriguing generalizations of 
prosobranch ecology is that in some places most 
species hatch as planktonic larvae, while in other 
places most species hatch as fully formed snails. 
The predominant hatching type varies both with 
latitude and with habitat. Typically many species 
have planktonic larvae at tropical sites and in 

shallow waters, while in the deep sea or in the 
arctic, most hatch metamorphosed (Thorson, 
1950). These generalizations raise two questions: 

(1) are species that hatch metamorphosed in cold 
water areas replaced by ecological equivalents 
with planktonic larvae in warm-water areas; and 

(2) is one hatching type replaced more completely 
in some habitat types than others? 


April 25,1977 

Vol. 91 (2) 

The latitudinal change in prevailing hatching 
ty'pe does not require species replacements. The 
change parallels a large change in community 
diversity. As long as most species added along the 
latitudinal gradient have swimming larvae, the 
prevailing hatching type will change, whether 
species with metamorphosing larvae are replaced 
or are about equally numerous everywhere. In 
the data presented by Thorson (1965) for Euro- 
pean prosobranchs, about equally many species 
with metamorphosed hatchlings are found at all 
latitudes, while the diversity of species with 
swimming larvae rises abruptly between 30°N 
and eO^N (Fig. 1). Thorson's data (Fig. 1) include 
50-60% of the total fauna and therefore 






o 100 - 



50 60 


FIG. 1. Pint of estimated number af ftpecies of prnnohrnnrh 
snaik hatching metnmorphoaed (triangles) and hatching as 
.•fwimming larvae (circles) for various European localities as a 
functon of latitude. Each paint is obtained by midtiplying the 
estimated total number of prosobranchs for the site by the 
fraction of species for each hatching type, as based on a sam- 
ple of iO-60% of known hatching lifpes. Data fnmi Thorson 
(19U and 1965). Solid figures and solid lines, mainland sites: 
open figures and dotted or dashed lines, island sites. The lines 
are fitted by linear regression and have the follouing r' 
valties: metamorphosed, mainland O.Oi, island 0.01; smmming 
larvae, mainland 0.81, island 0.87. 

estimates of faunal composition based on these 
are both relatively unbiased and comparable to 
each other. Within the 40-70" latitudinal range, 
and among prosobranchs as a whole, species 
hatching metamorphosed are supplemented 
rather than replaced by species with plantonic 
larvae. Figure 1 also demonstrates an additional 
habitat variable: isolation. At all latitudes, island 
sites have fewer species of both hatching types. 

Frequencies of the larval types also vary from 
one habitat to another. Most tropical .shore 
species have planktonic larvae (91% o( 21 species, 
Lewis, 1960; 100% of 13 species, Ostergaard, 
1950), while in deeper waters (here "deep" refers 
to waters in the range of lO-l(X) m) many species 
hatch metamorphosed (25%, Thorson, 1940a: 69%, 
Knudsen, 1950). Hatching types were obtained for 
relatively few species in these studies, and the 
selection undoubtedly reflects the particular tax- 
onomic groups these authors chose or were able 
to study. To confirm the habitat-larval type rela- 
tionships, further data are required. 

Larval types of many species have been 
reported incidentally, and these can be used to 
confirm the pattern of changes observed in the 
regional faunal studies. With this in mind. I have 
reviewed the published data on members of one 
major group, the superfamily Muricacea 
(including the thaidids). 


The available habitat descriptions (obtained 
from the papers cited or from standard works) 
fall into 4 major categories: intertidal rocky 
shores, oyster reefs, shallow-water sand bottoms, 
and deeper waters (10-100 m, as opposed to the 
deep sea). Thais cornnata, found on mangroves, 
fits into none of these categories, and is arbitrari- 
ly included with the oyster reef species. The 
oyster reef species appear to be found on more 
kinds of substrates than the other species are; in- 
dividuals of most of these species can be found 
feeding on clams on muddy bottoms or barnacles 
on rocky shores as well as on oysters. 

Larval types are summarized by wide lati- 
tudinal bands (Table 1). Latitudinal bands were 
chosen to approximate equatorial, tropical, sub- 
tropical, temperate, and boreal areas. Too few 

Vol. 91 (2) 

April 25, 1977 


TABLE 1. Percentage of species 0/ Muricaceans hatching as 
long-term veligers (more than 1 week) as a function of 
lot it tide and habitat. Number of species in parentheses. 

































data are available to identify local patterns, and 
therefore no attempt was made to accommodate 
more subtle features of species distributions. 

The latitudinal band for each species was ob- 
tained from the site at which observations were 
made rather than from the species range. Single 
sites were used to avoid the bias of including 
wide-ranging species in more than 1 band. How- 
ever, of 6 species studied by more than one 
author, 3 were studied in different latitudinal 
bands (Cuma turbinoides = Thais carinifera?, 
Occnebra japonwa = Tritonalia japonica, and 
Thais floridana = Thais haemastoma floridana) 
and are entered twice in Table 1. Three species 
were studied by two authors within the same 
latitudinal band: Thais fasciata (T. rustica). 
Acanthina lapilloides (A. spirata), Favartia 
ceUulnsus. These 3 species are entered only once 
in Table 1. 


Each species is listed as given by the original 
author, together with the approximate latitude of 
the original author's observations. 

Intertidal Rocky Shores 
Hatch as veligers: Thais bufo (Lamarck) 8''N 
(Natarajan 1957), Thais tissoti (Petit) S^N 
(Natarajan 1957), Vitularia salebrosa (King and 
Broderip. 1832) 9''N (D'Asaro 1970b), Thais 
tieltoidea Lamarck LTN (Lewis 1960), Thais 
flofidana Conrad 13°N (Lewds 1960), Thais patula 
Linnaeus 13°N (Lewis 1960), Cuma turbinoides 
Blv. 22°S (Risbec 1935), Thais rustica Lamarck 
25°N (D'Asaro 1970a), Thais carinifera (Lam.) 
27°N (Thorson 1940a), Jopas francolinuyn 
Bruguiere 27''N (Gohar and Eisawy 1967), Thais 

hippocastaneum (Lam.) 27"N (Thorson 1940a), 
Dicathais aegrota (Reeve 1846) 32"S (Phillips 
1969), Thais fasciata Rve. 32»N (Lebour 1945), 
Ocejiebrapoulsoni Carpenter 33°N (Fotheringham 
1971), Shasktrus festivus (Hinds) 33°N (Fother- 
ingham 1971), Morula marginalba (Blainville) 
33°S (Anderson 1967), Bedevina birileffl (Lischke) 
33°N (Amio 1957), Concholepas conchoiepas 
(Bruguiere) 39°S (Gallardo 1973). 

Hatch as snails: Favartia cellulosu^ (Conrad) 
25<'N (Raeihle 1966), Favartia nuceus (Morch) 
32°N (Lebour 1945), Thais dubia 34''S (Bokenham 
and Neugebauer 1938), Bedeva hanleyi (Angas) 
35''S (Anderson 1967), Acanthina lajnlloides 36°N 
(Hewatt 1934), Acanthina spirata (Blainville), 
37''N (personal observations), Nucella calcar 39°S 
(Gallardo, 1973), Ocenebra lumaria Yokoyama 
41°N (Luckens 1970), Ocinebra aciculata Lamarck 
43''N (Franc 1940), Ceratostoma foliatum 
(Gmelin) 48»N (Spight et al. 1974), Thais 
canaliculata (Duclos) 48°N (original), Thais 
emarginata (Deshayes) 48°N (original), Thais 
lamellosa (Gmelin) 48°N (original), Nucella 
lapfillus (Linnaeus) 54''N (Pelseneer 1910), Thais 
lima (Gmelin) 51°N (original). 

Oyster Reefs 

Hatch as veligers: Thais coronata Lam. 6°^ 
(Knudsen 1950), Thais haemastoma floridana 
(Conrad) 26"N (D'Asaro 1966), Purpura clavigera 
Kuster 37°N (Amio 1963), Purpura bronni 
Dunker41''N (Amio 1963). 

Hatch as snails: Eupleura caudata (Say) 37°N 
(MacKenzie 1961), Ocenebra japonica (Dunker) 
43°N (Amio 1963), Ocenebra japonica 47''N (Chap- 
man and Banner 1949), Ocenebra erinacea (L.) 
52°N (Hancock 1960), Urosalpinx cinerea (Say) 
52°N (Hancock 1959). 

Shallow-water Sand Bottoms 
Hatch as veligers: Chicoreus brunneus Link 
22°S (Risbec 1932), Hexaplex kosterianus Tapp. 
27''N (Thorson 1940a), Leptoconchus cumingii 
(Deshayes) 27''N (Gohar and Soliman 1963), 
Rapana thomasiana Crosse 37''N (Hirase 1928). 

Hatch as veliconchas and/or snails: Murex 
trapa Roding 8°N (Natarajan 19,57), Chicoreus 
mrgineus var. ponderosa Sowerby S^N (Natarajan 
1957), Chicoreus incamatus (Roding) 27°N (Gohar 


April 25,1977 

Vol. 91 (2) 

and EisawT 1967), Chicoreus ramomts (Linne) 
27»N (Gohar and Eisawy 1967). 

Hatch as snails: Chicoreus torrefactus (Sower- 
by) 18'S (Cernohorsky 1965), Ton'amnrex fem/».s 
(Reeve) 22°S (Murray and Goldsmith 1963), 
Chicoreus florifer Reeve 26°N (D'Asaro 1970), 
Chicoreus pomum Gmelin 26°N (D'Asaro 1970a), 
Calotrophon ostrearum (Conrad) 30°N (Radwin 
and Chamberlin 1973), Urosalpinx perrugata 
(Conrad) 30°N (Radwin and Chamberlin 1973), 
Hexaplex trunculu,'< (Linne) 43°N (Fioroni 1966). 

Deeper Waters 

Hatch as veligers: Hexaplex fvlvescens (Sow) 
28°N (Moore 1961). Rapana bidbosa Sol. 28»N 
(Thorson 1940a). 

Hatch as snails: Chioreits quadrifrons (Lam.) 
5°N (Knudsen 1950), Chicoreus senegalensw 
(Gmel.) 5°N (Knudsen 1950), Murex fasciatus 
Tryon 1880 10°N (Knudsen 1950), Muricopsis 
blaimnllei (Payraudeau) 41''N (Fioroni 1966 after 
Franc 1948), Murex brandaris Linne 43°N 
(Fioroni 1966), Ocenebra spec. 43°N (Fioroni 
1966), Trophon muricntus (Montagu) SO^N 
(Labour 1936), T)vphon truncahis (Str6m) 57''N 
(TTiorson 1946), Trophon clathratus (L.) var. Gun- 
neri Loven 65<'N (Thorson 1940b). 


The predominant type of hatching changes 
more markedly among rocky shore murica 
ceans than it does among prosobranchs as a 
whole (Fig. 1). In this habitat, all high-latitude 
species metamorphose before hatching, and all 
tropical species have planktonic larvae. The rock>' 
shore fauna is relatively well known, because it is 
accessible at all latitudes; therefore further work 
is unlikely to change this generalization. Species 
of one hatching type are completely replaced by 
ecological equivalents of the other along the 
latitudinal gradient. The two hatching types are 
mixed between 25-30° (Table 1), and studies at 
these latitudes should reveal the relative ad- 
vantages of the two hatching types, and possible 
instances of competition between them. A 
parallel latitudinal trend is observed among 
oyster reef species. 

Hatching types for shallow-water sand species 
and deep-water (10-100 m) species do not change 

in the same manner. Species with metamorphosed 
hatchlings prevail at most latitudes in both of 
these habitats. In the shallow-water sand habitat, 
one also finds an intermediate hatching type, a 
non-feeding Veliconcha that metamorphoses a 
few days after hatching. 

Considering all habitats, diversities of both 
hatching types are probably greatest at low lat- 
titudes. According to available data, the 
latitudinal gradient in hatching type is striking 
(Milekovsk>', 1971) and might imply a low 
number of tropical species that hatch metamor- 
phosed. However, a disproportionately large 
number of the tropical observations are on rocky 
shore species. Species from other near-shore 
habitats are likely to have metamorphosed hat- 
chlings at all latitudes. When these are included, 
species with metamorphosed hatchlings will pro- 
bably be shovra to be most diverse at lower 
latitudes. In the only whole-fauna available to 
date (Fig. 1), species with metamorphosed hatch- 
lings are more diverse at the lowest latitude 
(Portugal, 41°N) than at the highest. 


Amio, M. 1957. Studies on the eggs and larvae of marine 
gastropods. Part I../ Shunonosek-i Coll. Fisk 7: 107-116. 

Amio. M. 1963. A comparative embryology of marine 
gastropods, with ecological emphasis. J. Shinwnoseld ColL 
F-ish. 12: 229-.'353. 

Anderson, D. T. 1967. Further observations on the life 
histories of littoral gastropods in New South Wales. Proc. 
Linnean Sue. New South Walea 90: 242-251. 

Bokenham. N. A. H. and F. L. M. Neugebauer. 1938. The ver- 
tical distribution of certain intertidal marine gastropods in 
False Bay. with notes on the development of two of them. 
.4«H.A'(i/(!/.A/i«. 9:113-137. 

Cemohorsky. W. 0. 1965. The radula. egg capsules, and young 
of Murex (Chicoreus) torrefactus Sowerby. Veliger 8: 

Chapman, W. M. and A. H. Banner. 1949. Contributions to the 
life history of the .Japanese oyster drill (Tritonnlia japnnica) 
with notes on the other enemies of the OI>Tnpic Oyster 
((htrea lurida). Wiishinytim Dept. Fixh. Biol, kept 49A: 

U'Asaro. C. N. 1966. The egg capsules, embryogenesis. and ear- 
ly organogenesis of a common oyster predator, Thais 
haemastoma floridana (Gastropoda Prosobranchia) Bull 
Mar. Sci 16: 884-914. 

D'Asaro. C. N. 1970a. Egg capsules of prosobranch molluscs 
from South Florida and the Bahamas and notes on spawn- 
ing in the laboratory. Bull. Mar. Sci. 20: 414-440. 

Vol. 91 (2 

April 25. 1977 


D'Asaro. C. N. 1970b. Egg capsules of some prosobranchs from 

the Pacific Coast of Panama. Veliger 13: 37-43. 
Fioroni. P. 1966. Zur morphologie und embryogenese des 

Darmtraktes und der transitorischen Organe bei Prosobran- 

chiern (Mollusca, Gastropoda). Renie Suisse de ZooUxjie 73: 

Fotheringham. N. 1971. Life history patterns of the littoral 

gastropods Shaskyus feMiinis (Hinds) and Ck-enebm /Wwwi 

Carpenter (Prosobranchia: Muricidae).&()%i/52: 742-757. 
Franc. A. 1940 Recherches sur le developpement D'Ocinehra 

aacidata, Lamarck (Mollusque gasteropode). Bull. Biol. FV. 

Belg. 74: 327-345. 
Gallardo, C. 1973. Desarrollo intracapsular de Concholepas 

corwholejxis (Bruguiere) (Gastropoda Muricidae). Museo Nn- 

Clonal de Historia Nntuml Santiago de Chile Publ. Oca.'!. 16: 

Gohar, H. A. F. and A. M. Eisaw>'. 1967. The egg-masses and 

development of five rachiglossan prosobranchs (from the 

Red Sea). Pubis, mar. biol. Stn. Ghardaqa 14: 215-268. 
Gohar. H. A. F. and G. N. Soliman. 1963. On the biology of 

three coralliophilids boring in living corals. Pubis, mar. biol. 

Sta. Al Ghardaqa 12: 99-126. 
Hancock, D. A. 19.59. The biology and control of the American 

whelk tingle Uro.'<alpinr cinerea (Say) on English oyster 

beds. Fishvrii Invest. (London) Ser. H Vol. XXII (10): 1-66. 
Hancock. D. A. 1960. The ecology of the molluscan enemies of 

the edible mollusc. Proc. Malacol. Soc. London 34: 123-143. 
Hewatt, W. G. 1934. Ecological studies on selected marine m- 

tertidal communities of Monterey Bay. Ph. D. TTnesis, Stan- 
ford University. 
Hirase, S. 1928. Eiablage von Rapana thomasiana Crosse.Ar- 

chivfur Molluskenkunde 60: 173-178. 
Knudsen, J. 1950. Egg capsules and development of some 

marine prosobranchs from tropical West Africa. Atlantide 

Rept. 1: 85-130. 
Lebour, M. V. 1936. Notes on the eggs and larvae of some 

Pl\-mouth prosobranchs. J. Mar. Biol. Assn. U. K. 20: 

Lebour, M. V. 1945. The eggs and larvae of some prosobranchs 

from Bermuda. Proc. Zool. Soc. London 114: 462-489. 
Lew-is, J. B. 1960. The fauna of the rocky shores of Barbados, 

W. I Canadian J. Zool. 38: 391-435. 
Luckens, P. A. 1970. Variation of shell characters of a species 

of Ocenebra (Mollusca; Gastropoda) at Asamushi. Sci. Rept. 

TShoku Univ. (Ser. IV, Biol.) 35: 149-1.59. 
MacKenzie, C. L. Jr. 1961. Growth and reproduction of the 

oyster drill Eupleura caudata in the York River. Virginia. 

£co/o5fr/ 42: 317-338. 

Mileikovsky. S. A. 1971. Types of larval development in 

marine bottom invertebrates, their distribution and 

ecological significance: a re-evaluation. Afar. Biol. 10: 

Moore, D. R. 1961. The marine and brackish water mollusca of 

the State of Mississippi, ft/7/fle.s. Repts. 1(1): 24-27. 
Murray, F. V. and M. H. Goldsmith. 1963. Some observations 

on the egg capsules and embryos of Torvamurez territus 

(Reeve, 1845). ./. Malacol. Soc Australia 7: 21-25. 
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development of some prosobranchs from the Gulf of Mannar 

and the Palk Bay. Proc. Indian Acad. Sci. 46(3): 170-228. 
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Hawaiian marine gastropods. Pacific Science 4: 75-115. 
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Gastropodes. Mem. Acad. Royale Belgique Ser. 2 Vol. 3 pp. 

Phillips, B. F. 1969. The population ecology of the whelk 

LHcathais aegrota in Western Australia. Aust. J. Mar. 

FVeshiv. Re.^. 20: 225-265. 
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development in stenoglossan gastropods. TYans. San Diego 

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Conrad. yl?in, Rept. A mer. Malacol. Unirni 1966: 28. 
Risbec, J. 1932. Notes sur la ponte et le developpement de 

mollusques gasteropodes de Nouvelle-caledonie. Bull. Soc. 

Zool. France 57: 358-375. 
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neo-calendoniens. Bull. Soc. Zool. FVance 60: 387-417. 
Spight, T. M., C. Birkeland and A. Lyons. 1974. Life 

histories of large and small murexes (Prosobranchia: 

Muricidae). Afar. Biol. 24: 229-242. 
Thorson, G. 1940a. Studies on the egg masses and larval 

development of Gastropoda from the Iranian Gulf. Dan. Sci. 

Invest. Iran 2: 159-238. 
Thorson, G. 1940b. Notes on the egg-capsules of some North- 
Atlantic prosobranchs of the genus Troschelia. 

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Fisk. -og Havunders.. ser Plankton. 4: 1-523. 


April 25,1977 

Vol. 91 


Walter 0. Cernohorsky 

Auckland Institute and Museum 
Private Bag, Auckland, New Zealand 


The new subfititute name Conus viola is here proposed fur the hoinouymous 
C. violaceus Reeve, from the tropical West Pacific region. 

Conus viola Cernohorsky, new name 
Figs. 1 - 3 

1844. Co«M.s violaceus Reeve, Conchologia Iconica, 
vol. 1, pi. 44, fig. 241; 1858 Sowerby, Thesaurus 
Conchyliorum, vol. 3, p. 45, pi. 208, fig. 537; 
1875 Weinkauff, Martini & Chemnitz Syst. 
Conchyl. Cabinet, ed. 2, vol. 4, pt. 2, p. 76, pi. 
46, fig. 11; 1937 Tomlin, Proc. Malac. Soc. Lon- 
don, vol. 22, p. 328 (erroneously synonymized 
with C luteus Sowerby^ [non C. violaceus 
Gmelin, 1791] 

1884. Conus violaceus Reeve [pars], Tryon, 
Manual of Conchology, vol. 6, p. 88, pi. 28, fig. 
82 (only) 

1964. Conus luteus var. Sowerby, Marsh & Rip- 
pingale. Cone shells of the world, p. 124, pi. 18, 

fig. 7 {non Sowerby, 1833) 
1972. Cvnus species Hinton, Shells of New Guinea 

and the central Indo-Pacific, p. 82, pi. 40, fig. 6. 
1975. Conus molaceus. C. tendineus or Conus sp.? 

Leehman, Hawaiian Shell News, vol. 23, No. 6, 

p. 6, text figs. 

Type locality: Matnog, Island of Luzon, Philif)- 

Type specimens: TTie three syntypes of C. 
molaceus Reeve, accompanied by a label which 
bears Tomlin's remark = luteus Broderip, are in 
the British Museum (Nat. Hist.), London. The 
specimen measuring 41.0 mm in length and 15.0 
mm in width, is here selected as the lectotype of 
C. violaceus ( = C. viola new name). 

Conus violaceus was first described in 
literature by Reeve (1844), who based his 

FIGS. 1-2. h'ctdtyi)!' (i/ ('onus violaceus Rerve (= C. viola 
Cernohorsky, new name: B.M.N.H.. length 1,1.0mm. uMlh 15.0 
mm. 3. Specimen o.f C. viola from Bathurst Id., Nth. 

Australia: Icni/th ■'io.S mm. u-idth .Hi mm. 4-5, Topotype of 
C. luteus Sowerby, from Anaa Id.. Tiiamotus; B.M.N.H., 
length SS.Omm. 

Vol. 91 (2) 

April 25, 1977 


diagnosis on three specimens from the Cuming 
collection. Reeve's C. violaceus, however, is a 
primary homonym of C. vwlacem Gmelin, 1791, 
which is an earlier name for the Indian Ocean 
species C. tendineus Hwass in Bruguiere, 1792. 
Tomlin (1937) did not propose a replacement 
name for the homonymous C. violaceus Reeve, as 
he considered this species to be synonymous with 
C. luteus Sowerby, 1833. 

C. viola and C. luteus are similar but quite 
distinct species, with C. viola known only from 
an area between the Philippines and North 
Australia, whereas C. luteus is widely distributed 
throughout the tropical Pacific. The average size 
of C. viola is about 50 mm, the shell is cylin- 
drical, the first 2-3 post-embryonic whorls are 
finely nodulose, the penultimate whorl is inflated 
and telescopic in appearance, sutures are firmly 
but irr^ularly adpressed, the outline of the body 
whorl is cylindrical with the first two-thirds of 
the body whorl descending almost vertically 
before tapering towards the base, the aperture is 
narrow at the start but slightly flaring basally, 
and the sculpture consists of 6-10 spiral threads 
on the spire whorls, obsolete spiral threads on the 
body whorl and up to a dozen close-set cords at 
the base. Fresh specimens are pale violet and or- 
namented with brown spots on the spire whorls, 
three broad but often dilacerated brovra bands on 
the body whorl which are usually interrupted in 
the centre of the whorl by a pale band, and spiral 
rows of small brown spots, aperture pale violet. 

C. luteus is considerably smaller, averaging 
about 30 mm in length, the spire is short and 
convex, whorls are not inflated but tight, the 2-3 
post-embryonic whorls are smooth, the sutures 
are narrowly canaliculate, the shoulder is 
moderately broad, smooth and sloping and the 
body whorl tapers rapidly toward the slender 
base; shell glossy, obsoletely spirally striate on 
the body whorl, the arcuate axial striae on the 
spire whorls are crisper and spiral threads fewer 
and the aperture is uniformly narrow and does 
not flare basally. The colour is yellow, orange, 
pink or rose-red, the centre of the body whorl has 
a narrow white band or blotches which are 
bordered by quadrate, irregular and distinctly 
smudged dark brown spots, and spiral rows of 
dark brown interrupted lines are present in some 

Dark coloured specimens of C. viola have been 
illustrated by Leehman (1975) and the banded 
form by Hinton (1972). The lectotype of C viola is 
a form where the brown bands are dilacerated in- 
to longitudinal zones. 


Hinton, A. 1972. Shells of New Guinea and the Central Indo- 

Pacific. R. Brown & Associates Pty. Ltd., Port Moresby, and 

Jacaranda Press, Milton, 94 pp., 44 col. pis. 
Leehman, E. G. 1975. Conus confusion. Hawaiian Shell News. 

23(6): 6, text figs. 
Reeve, L, 1843-44. Conchologia Iconica; monograph of the 

genua Qmits. L. Reeve, London, vol. 1. 47 pis. 
Tomlin. J. R. le B. 19.37. Catalogue of Recent and Fossil Cones. 

Proc. Malae. Soc. London, 22: 205-330. 

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April 25,1977 

Vol. 91 (2) 


Tom M. Spight 

Woodward-Clyde Consultants 

3 Embarcadero Center, Suite 7()0 

San Francisco, Calif. 94111 


Thais canaliculata appears to be in the course of evolving from one 
reproductive mode (!()()% fertility) to another fprovmon of nurse eggs for em- 
bryos). In some populatiori% all eggs are fertile. In other populations, as few as 
16% in each capsule may he fertile and the infertile eggs are used as nurse 
eggs by the embryos. If T. canaliculata is to complete the transition to nurse- 
egg feeding, two major adaptive problems must be solved: fertility must be 
regulated, arui new larger hatchlings must become much more likely to survive 
to maturity. 

Some Thais canaliculata (Duclos, 1832) 
females produce infertile eggs, and these are used 
by the embryos as nurse eggs, while other 
females produce only fertile eggs (Lyons and 
Spight 1973). These variations in reproductive 
mode may indicate that T. canaliculata is in the 
process of abandoning one mode in favor of 
another. This paper will examine available data 
on fertility in order to evaluate this hypothesis. 


Egg capsules were collected at Cattle Point and 
South Beach (on the southeast tip of San Juan 
Island, Washington) during May, 1970, at Cattle 
Point during May, 1972, and near Friday Harbor 
during May and August, 1972. One of the Friday 
Harlx)r clusters was attended by a 44-mm female, 
and one by a 31-mm female. Capsules were 
opened shortly after collection, and contents (eggs 
and/or embryos) were counted. The 41-mm 
female continued to deposit capsules while kept 
in a laboratory aquarium. Some of these capsules 
were kept to obtain embryo counts. 


Capsules from Cattle Point and South Beach do 
not contain infertile eggs. The capsules collected 
during 1970 contained cleaving eggs or early em- 
bryos, and all eggs were developing. The average 

1970 capsule was 8.23 mm long (N = 23, SD = 
0..53) and contained 28.1 embn,'os (SD = 8.35). 
The 1972 capsules, which contained embryos near- 
ly ready to hatch, were slightly smaller (8.04 mm, 
N = 17, SD = 0.72), and contained W/o fewer 
embryos (23.5, SD = 4.39). Therefore, embryo 
numbers do not decline significantly during 
development (Fig. 1, open vs. solid circles). 

Capsules from Friday Harbor do contain infer- 
tile eggs. Several capsules from the 44-mm female 
were opened, and of these, 8 contained embryos 
that had almost reached the feeding stage. From 
16% to 92% of the eggs in these capsules were 
developing (mean, 56%). I found feeding embryos, 
nurse eggs, and debris of broken nurse eggs in 
each of the capsules deposited by another female. 
Only 35% of the intact eggs were developing. Ac- 
tual fertility must have been even lower, since 
some of the nurse eggs had already been torn 
apart and consumed. 

The number of eggs per capsule is significantly 
correlated with capsule size (capsule length, ex- 
cluding the stem; Fig. 1). When all counts from 
Cattle Point and South Beach capsules, and 
counts of eggs plus embryos from Friday Harbor 
capsules are included, the logarithm of capsule 
height (X) accounts for 34% of the variation in 
the logarithm of egg count (Y), and the following 

Vol. 91 (2) 

April 25, 1977 


linear regression between these variables is ob- 

Y = 1.7299 X - 0.1527 

for a total of 55 capsules (F , „ = 27.0891, P < 
0.01). Almost all of the embryo counts for the 
Friday Harbor capsules fall well below this com- 
mon line (solid triangles, Fig. 1). 













&/ ■ 






o (2i 







"•• J 


X: \ 




o • 
• o 







A A 













1 1 1 

7 8 9 10 II 12 


FIG. L Contents of capsules of Thais canaliculata from 
San Juan Island. WashingUm. Circles indicate capsules from 
Cattle Point and South Beach. Open circles and the dotted 
line indicate early embryos, while solid circles and the da.'iheil 
line indicate late embryos. Triangles indicate capsides from 
Friday Harbor. Open triangles and the thin solid line repre- 
sent eggs, while .tolid triangles represent embryos. The heavy 
line is the calcidated regression fw all data (except .solid 
triangles). Individual capsides from Friday Harbor are 
represented by 2 triangles (one empty, one filled) when both 
egg and embryo counts were obtained. All lines are fit by 
least-squares linear regression. 


Fertility of Viais canaliculata eggs varies 
strikingly around San Juan Island, Washington. 
In some populations, virtually all eggs become 
hatchlings. Counts of early and late embryos dif- 
fer by only 16% at South Beach and Cattle Point. 
Larger developmental mortalities have been 
reported for most other muricid species without 
nurse eggs (14-58%; Cole 1942, Federighi 1931, 
Hancock 1959, Phillips 1969). In other popula- 
tions, many eggs are infertile, and these are used 
as nurse eggs by the embryos. The T. cana- 
liculata populations of Fig. 1 may be at different 
stages of the process of changing from one 
reproductive mode (100% fertility) to another 
(provision of nurse eggs). 

If reproductive mode is changing, what is the 
direction of the change? T. canaliculata embryos 
possess a feeding mechanism unlike any other 
that has been described (Lyons and Spight, 1973). 
Firstly, this mechanism could have been in- 
herited, but if so, the ancestor has no mid- 
latitude species that produce nurse eggs among 
its descendents. Secondly, T. canaliculata may 
have evolved a low-fertility reproductive mode 
early in its history and is now abandoning this 
mode. A third explanation is most simple because 
it postulates the fewest evolutionary changes: 
some T. canaliculata populations are utilizing 
nurse eggs for the first time. 

If the reproductive mode is changing, how far 
has the change progressed? The fertility data pro- 
vide a kind of measure of progress because as fer- 
tility varies from capsule to capsule, hatching 
size also varies, and females whose fertility is 
variable will in the long run be less fit than those 
with constant fertility and offspring of the op- 
timum size. If large hatchlings are much more 
likely to survive through the post-hatching period 
than small ones are, then females that produce 
small hatchlings will be at a disadvantage; if not, 
females that produce small hatchlings will be the 
most fit because they produce more offspring. 
Among the Friday Harbor capsules, some con- 
tained only a few embryos (which would become 
large hatchlings), while nearly all of the eggs in 
others were fertile. Fertility varies much more 
than it does among Acanthina spirata capsules. 


April 25,1977 

Vol. 91 (2) 

although A. spirata has about the same average 
fertility (Spight, 1976). Fertility is unregulated in 
Friday Harbor populations, but selection favoring 
regulation should be strong and therefore 
reproductive characteristics should be changing 
rapidly at the present time. 

Each infertile egg reduces its parents' fecundi- 
ty. Since only 35-56% of the eggs are fertile, 
Friday Harbor females are producing less than 
half as many embryos as females from Cattle 
Point are (compare the filled triangles of Fig. 1 
with other symbols). If the number of surviving 
offspring per f)arent is to be similar at the two 
sites, then each Friday Harbor offepring must 
have a greater chance of surviving. Larger hatch- 
lings are generally more likely to survive through 
the post-hatching period than small ones are 
(Spight 1972). T. canaliculntn eggs range from 
590 to 650 ^m and eggs from Cattle Point become 
hatchlings of 1150 to 1300 jim. When only 56% of 
the eggs are fertile, the average embryo will have 
nearly twice as much yolk as would an embryo 
without nurse eggs, and therefore Friday Harbor 
hatchlings should weigh twace as much as those 
from Cattle Point. The large Friday Harbor 
hatchlings should be more likely to survive than 
the small ones from Cattle Point. However, if 
survival is dependent on size alone, then the op- 
timum hatching size is the same for all parents 
of T. caudlicidatcu and an increase in hatching 

size will result in a net decrease in the number 
of hatchlings surviving through the critical post- 
hatching period (Smith & Fretwell, 1974). If 
nurse-egg feeding, accompanied as it is by 
decreased fecundity, is to be evolutionarily suc- 
cessful, then the optimum hatching size must be 
altered. Further work will be required to deter- 
mine whether necessary changes are in progress 
for T. canaliculata. 


Cole, H. A. 1942. The American Whelk Tingle. Urasalpiiijc 

cinerea. on British oyster beds. Jour. Mar. Biol. Assn. 25: 

f'ederighi. H. 1931. Studies on the oyster drill, i'msalpinx 

riiicrm. Ridl. U. S. Bureau 47: 8.5-11.5 (19.31). 
Hancock. I). A. 19.59. The biology and control of the American 

Whelk Tingle, Urosalpini cinerea. on Eiiglish oyster beds. 

Fishery Ini'esl. Lond. 22(2): 1-66. 
Lyons, A. and T. M. Spight. 1973. Diversity of feeding 

mechanisms among embryos of Pacific Northwest TTiots. 

Veiiger 16: 189-194. 
Phillips. B. F. 1969. The population ecology of the whelk 

Dicathais aegrota in Western Australia. Australian Jour. 

Mar Fi-e.^hu: Res. 20: 225-265. 
Smith. C. ('. and S. D. Fretwell. 1974. The optimal balance 

between size and number of offspring. Amer. Natur. 108: 

Spight, T. M. 1972. Patterns of change in adjacent populations 

of an intertidal snail, Thais lamellosa. Ph. D. Thesis, 

University of Washington. 
Spight. T. M. 1976. Hatching size and the distribution of 

nurse eggs among prosobranch embroys. Biol. Bull. 150: 



Branley A. Branson 

Eastern Kentucky University 
Richmond, Kentucky 40475 


A vprij hiiyr iiiipiildtidn o/ Cipangopaludina chinensis ((iraii. IS.SJ,) « irpiirlcil 
fnini IjiL-c (abrade an (hra.s hliiiiil in tlic I'lKp't Smnid r('(jli>ii nf /r( stern 

Various authors have reported the estab- viviparid snail, Cipangopoludina chinen.'^!^ (Gray, 
lishments of populations of the freshwater 1834), in widely separated sections of North 

■ Part of a larger study supported by Sigma-Xi-Resa and In- America, assigning several specific epithets to the 
stitutional grants. snails (Dundee, 1974), including Viviparus 

Vol. 91 (2) 

April 25, 1977 


malleatun Reeve and V. stelmaphoru^ 
Bourguignat. Previous reports of the species from 
the state of Washington are restricted to a 
population in Green Lake at Seattle (Hanna, 

The population reported here was thriving in 
1973 in Lake Cascade at Moran State Park on 
Orcas Island, the largest and most highly tourist- 
oriented body of land in the San Juan Island off 
the Washington coast. Although I made no at- 
tempt at estimating population size, 56 in- 
dividuals were secured in approximately 30 
minutes from an area no larger than two square 

meters. The smallest individual is 7.0 mm in total 
length, and the largest 44.0 mm, indicating, of 
course, that reproduction was occurring at that 
time. One shell and operculum were deposited at 
the Delaware Museum of Natural History (no. 
106584) as a voucher specimen. 


Dundee, D. S. 1974. Catalog of introduced mollusks of eastern 
North America (north of Mexico). Sterkiana 55: 1-37. 

Hanna. G. D. 1966. Introduced mollusks of western North 
America. Occ. Pap. Calif. Acad. Set. 48: 1-108. 


Fred G. Thompson 

Florida State Museum 

University of Florida 

Gainesville, Florida 32611 

Mcleania is a genus of medium-sized depressed 
helicoid land snails in which the species are 
characterized by having a series of nodelike ser- 
rations along the peripheral keel of the shell. Un- 
til now the genus was thought to be monotypic 
and endemic to Puerto Rico (see van der Schalie, 
1948:70) where the type species, M. darlingtnni 
Bequaert and Clench was discovered by Philip J. 
Darlington, Jr. in 1938. Bequaert and Clench 
(1939:283-284) tentatively placed Mcleania in the 
Cepolidae (= Xanthonichidae, see Baker, 1956) 
because of resemblances in size and shell shape 
to some Hemitrochus. Baker (1940: 55-57) 
demonstrated that the reproductive anatomy of 
Mcleania is similar to that of Thysanopkom. Cur- 
rently Mcleania, Thysanophora, and allied genera 
are placed in the Thysanophorinae, a subfamily 

During June, 1974, and January, 1976, I col- 
lected shells of two undescribed land snails from 
the Barahona Peninsula, Dominican Republic. 
One species is described in this paper. The second 

remains undescribed because it is represented by 
a single immature shell that does not show 
definitive characteristics of its species. These two 
snails are tentatively assigned to Mcleania 
because of similarities in shell structure to M. 
dmiingtoni. They differ from M. darlingtnni in 
important characteristics of the sculpture, as well 
as several other traits. No live specimens of the 
two new taxa were found, and a more satisfac- 
tory basis for relating them to M. dariingtoni 
cannot be given at this time. 

Field work in the Dominican Republic was 
sponsored by the Florida State Museum and the 
National Geographic Society, Committee for 
Research and Exploration. I am grateful to of- 
ficials of both organizations for making this field 
work possible. 

Mcleania tumidula new species 
(Fig. 1, A-C) 

S/?r//. -Depressed helicord, about 0.,53-0.67 
times as high as wide; medium sized, being about 


April 25,1977 

Vol. 91 (2) 

FIG. 1. A-C Mcleania tumidula neiv species, holotifpe (UF 
227:16). U.6 mm in width. D-F Mcleania darlin^imi Be- 

1.5 mm wide. Color uniform light brown. Shell 
opaque. Spire low, obtuse, nearly flat sided, 
slightly convex in outline. Base inflated. Whorls 
rapidly increasing in size, keeled, with about 
19-21 obliquely compressed knobby serrations 
along the periphery that form a scalloped fold 
around the shell. 'Die peripheral interior of the 
shell is indented beneath the knobs. Body whorls 
nearly flat above the periphery, strongly inflated 

quaert and Clench: 30 km. N.N. W.. 3 km K Ponce. Puerto 
Rim. mm-ll.iO m. alt. (UF 22738). 

below: descending very slightly along its last 
quarter. Umbilicus narrow, about 1/25 the 
diameter of the shell. Umbilicus partially 
obscured by reflected columella. Adult shell with 
3.6 whorls, and having 1.4 embryonic whorls. 
First embryonic whorl smooth. Subsequent em- 
bryonic portion with weak incremental growth 
wrinkles. First quarter of post -embryonic whorl 
with fine incremental thread-striations that are 

Vol. 91 (2) 

April 25, 1977 


replaced rapidly by heavy cord-like folds extend- 
ing halfway across the whorl from the suture. 
Folds more or less alternating with compressed 
knobs along the periphery. Superimposed on the 
cords is an oblique series of irregular, fine zig-zag 
striations that tend to become corrugated near 
the periphery and on the knobs. Base of shell 
with fine, irregular, incremental striations bear- 
ing superimposed and finer, short, scattered, zig- 
zag striations that tend to corrugate the base. 
Aperture broadly auriculate, deeply indented by 
previous whorl. Peristone simple, thin, weakly 
reflected, incomplete across parietal wall. Dorsal 
lip nearly straight. Columellar margin moderate- 
ly reflected over umbilical area. Parietal callus 
thin, transparent, strongly recurved near um- 
bilicum. nearly straight otherwise. 

Measurements in mm of the three known 
specimens are: 






Aperture H. 


Aperture W, 
















Type Locality— DominicsLn Republic, Barahona 
Prov., Loma Cana Brava, 6 km. E, 6 km. NNE 
Polo, 1370 m. alt. Holotype: UF 22736: collected 
18 January, 1976 by Fred G. Thompson. Para- 
types: UF 22735(2); same locality as the holotype. 

The type locality is in a wet mountain forest 
at the crest of the mountain Loma Cana Brava. 
The microhabitat occupied by the snail was not 
determined for live specimens were not en- 
countered. The shells comprising the type series 
were found on the ground under limestone slabs 
on densely shaded moss and lichen covered knolls. 

Remarks— Mcleania tumidida can be compared 
with two other species, M. darlingtoni from Puer- 
to Rico and another undescribed species from 
Hispaniola to which it is more closely related. It 
differs from M. darlingtoni in numerous details. 
The shell is much larger, attaining a major 
diameter of about 15 mm. It has a broadly obtuse 
raised spire, resulting in a height/width ratio of 
about 0.53-0.67. The whorls are much more in- 
flated, and have more (19-21) but much weaker 

serrated nodes per whorl along the periphery. 
The umbilicus is much narrower, being about 
1/25 the width of the shell. The peristome is in- 
complete across the parietal wall, and the outer 
lip is only slightly reflected. The periostracum is 
nearly smooth, having weak incremental stria- 
tions and poorly defined oblique anastomosing 
wrinkles. The embryonic whorls are smooth in- 
itially, with weak incremental sculpture follow- 
ing the first whorl. 

M. darlingtoni is characterized by numerous 
pecularities (Fig. 1, D-F). It attains a major 
diameter of about 12 mm, and is planispiral with 
a height/width ratio of about 0.36-0.38. The 
whorls are relatively small in caliber and have 
about 12-16 strong protruding nodes along the 
periphery. The umbilicus is very broad and fun- 
nel shaped, being about 1/3 the width of the 
shell. The peristome is complete and the aperture 
is slightly free from the preceding whorl. The 
lusterless periostracum bears numerous course in- 
cremental threads and fimbriations that form 
scattered tufts on the base and apex. The 
peripheral serrations are coursely marked with 
radial periostracal fimbriations. Finally, the em- 
bryonic whorls have rather course, strongly ob- 
lique anastomosing wrinkles. 

The differences between M. tumidida and M. 
dnrlimjtiini are numerous and of such a mag- 
nitude that a congeneric assignment of the two 
species is only provisional. Most fundamental of 
these differences is the sculpture. Until the soft 
anatomy of M. tumidula is investigated the 
systematic relationships and biogeographic im- 
plications must be interpreted with caution. 

An additional undescribed Mcleania occurs in 
the Sierra de la Salle north of Pedernales, Peder- 
nales Prov., Dominican Republic. A single im- 
mature shell (UF 22737) was collected 1 km. 
south of Altagracia, at 750 m. altitude in a cocao 
grove. Compared to M. tumidida this other 
species has course, irregular radial sculpture on 
the spire, is nearly planispiral, and has a wide 
umbilicus that is about 1/6 the diameter of the 
shell. In other aspects it is more like M. tumidula 
than M. darlingtoni. 


April 25.1977 

Vol. 91 (2) 


Baker. H. B. 19.56. Family names in Pulmonata. The Nautiltis 

69: 128-i:?9. 
Baker. H. B. 1940. Some Antillean Sagdidae and Polygyridae. 

The Nuut iliix 54: 54-62. 

Qench. Wm. J. and J. Bequaert. 1939. Mcl€ new genus of 
land mollusks from Puerto Rico. Meniorids dp la Siiripdntt 
Ciibnmi fie Histinia Natural 13: 283-284; pi. %. fig. 4-6. 

van der Schalie. H. 1948. The land and fresh-water mollusks 
of Puerto Rico. Misc. Publ. Museum ofZool. Unii: Mich. 70: 
1-133; pis. I-XIV. 


Alberto Carcelles, well-known and leading 
malacologist of Argentina, died Januar\' 23. 1977. 
in Alta Gracia. Cordoba. Argentina, at the age of 
81. Dr. Carcelles taught at the University in 
Buenos Aires and was for years Chief of the In- 
vertebrate Section, in the Museo Argentina de 
Ciencias Naturales. He was bom in Buenos Aires 
on July 18, 1897. He authored many works on the 
marine mollusks of Uruguay and Patagonia. 
Among his students was Dr. J. J. Parodiz of 
Pittsburgh. Pa. 

John Dyas Parker, malacological archivist for 
the Delaware Museum of Natural History and 
long-time assistant to Henry A. Pilsbn,' at the 
Academy of Natural Sciences of Philadelphia, 
died February 2, 1977, of a heart attack, in Penn- 
sylvania, at 61. He stimulated interest in mol- 
lusks among amateurs who funded the Pilsbr>' 
Chair of Malacology, and was a co-founder of the 
Philadelphia and Wilmington Shell Clubs. He 
was active in paleonto logical field work and cave 
exploration. Jack was born June 5, 1915. in 
Woodhaven, Long Island, N. Y. where he is now 

Willard Lee Mohorter, fonner publisher and 
private shell collector, died October 19, 1976, in 
Cincinnati, Ohio, at the age of 88. He and his late 
wife travelled extensively from 1936 to 1975 in 
search of mollusks. He was honorary curator of 
mollusks at the Cincinnati Museum of Natural 
Histor>' and donated part of his collection to that 
institution. He was born in Kiamensi, Delaware, 

October 4, 1888. A short, posthumous biography 
of "Mr. Mo" appeared in the Hawaiian Shell 
Npuv. February 1977. 

Esther Brooks Hadley, well-known shell dealer 
in Newton, Massachusetts since 1936, died in 
North Adams, Massachusetts, on September 9, 
1976 at age 87. Formerly, she worked for the 
Veterans Administration in Boston. She and her 
late husband, F. Knight Hadley, operated a shell 
mail order business for forty years. Her collection 
is for sale by her son, Norman, of Jacksonville, 
Vermont 05432. 

Kenneth R(ichard) H(odgson) Read, biochemist 
and marine biologist at Boston University, died 
February 24. 1977. at 48, in Boston, Mass. He was 
well-known for his underwater photography, and 
published on myoglobins in mollusks. He was 
born Spetember 9. 1928, in Dinas Powis, Wales, 
and obtained a Ph. D. at Harvard University in 

Albert B(ernhard) Kettell, for years a pastor 
of the United Church of Christ in New England, 
an Army Chaplain during World War II, and an 
ardent shell collector, was born in Somerville, 
Mass., March 7, 1896. He was a member of the 
A.M.U. for 25 years and a former President of 
the Connecticut Valley Shell Club. Reverend 
Kettell amassed a large collection of shells, and 
retired to Clearwater, Florida, where he died 
December 30, 1976, at the age of 81. He is sur- 
vived by his wife, Clara Dito Kettell. See Ameri- 
can Malnrologi<>tii. 1975 supplement, p. 555. 


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It is becoming increasingly important for 
future research purposes that an identified sam- 
pling of species mentioned in publications be 
deposited in a permanent, accessible museum 
specializing in moUusks. This is particularly 
true of moUusks used in physiological, medical, 
parasitological, ecological, and experimental 

The Delaware Museum of Natural History 

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JULY 1, 1977 



Vol. 91 
No. 3 

A quarterly 

devoted to 

malacology and 

the interests of 


Founded 1889 by Henry A. Pilsbry. Continued by 

Editor-in-Chief: R. Tucker Abbott 


urrington Baker. 



Dr. Arthur H. Clarke, Jr. 
Division of Molluslts 
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 
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Dr. Arthur S. Merrill 
Biological Laboratory 
National Marine Fisheries Service 
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Division of MoUusks 
U. S. National Museum 
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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 
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Division of Biology 

School of Marine and Atmospheric Science 
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Volume 91, number 3 — July 1, 1977 


William K. Emerson 

Notes on Some Indo-Pacific Species of Modi w (Gastropoda; Tonnacea) 81 

Helen DuShane 

A New Abyssal Amaea (Gastropoda: Epitoniidae) from the North Eastern Pacific Ocean ST''' 

Helen DuShane 

Epitonmm textimattum, a New Gastropod from the West Coast of Mexico 89 

Craig M. Doremus and Willard N. Harman 

The Effects of Grazing by Physid and Planorbid Freshwater Snails on Periphyton 92 

Ralph W. Dexter 

A Further Note on Geologic Changes in the Relative Size of Bivalve Shells 96 

Kathleen A. Burky and Albert J. Burky 

Buoyancy Changes as Related to Respiratory Behavior in an Amphibious Snail, 

Pomacea urceus (Muller), from Venezuela 97 

Clement L. Counts, III, John M. Dingess and James E. Joy 

The Electrocardiogram of the Freshwater Bivalve Lcimp.s-i'/is radiata (Bivalvia: Unionidae) 105 

Dee S. Dundee 

Observations on the Veronicellid Slugs of the Southern United States 108 

Steven T. Malek 

VeroniceUa occidentalis in Louisiana 115 

Ralph W. Taylor, Michael P. Sweeney and Clement L. Counts, III 

Use of Empty Gastropod Shells (Polygridae) by Pseudoscorpions 115 

Publications received 117 

)1 (:5) 

Julv 1, 1977 



William K. Emerson 

American Museum of Natural History 
New York. New York 10024 


Descriptive and distributional data are given for three poorly known and 
misunderstood species of Morum from the Indo-Paciflc. Additional specimens of 
Morum (Oniscidia) exquisitum are reported from the Subi Sea, and records other 
than those from the Philippines are rejected. Morum (0.) praeclarum, a species 
previously reported from deep water off Natal and Zuiuland. South Africa is 
reported from four stations in the western Indian Ocean. The recorded range of 
Morum (Herculea) ponderosum is extended to include New Caledonia and the Pit- 
cairn Islands. 

Specimens of two poorly known Indo-Pacific 
species of the genus Morum, namely: Morum ex- 
quisitum (Adams and Reeve, 1848) and M. 
praeclarum Melvill, 1919, have recently come to 
the attention of the writer. Morum exquisittim 
was described from a unique specimen obtained 
by Arthur Adams in the Philippines during the 
celebrated voyage of the HMS Samarang to the 
western Pacific and Indian Oceans, from 1843 to 
1846. Despite the fact that this species, based on 
the type specimen dredged in the Sulu Sea, was 
well-described and illustrated by Adams and 
Reeve (1848, 1850) and by Reeve (1849), the iden- 
tity of this taxon has remained uncertain owing 
to its extreme rarity in collections. Most subse- 
quent workers followed Tryon (1885) who con- 
sidered it to be conspecific with Morum 
ponderosum (Hanley, 1858), a distinct species 
originally described from an unknovra prove- 
nance. The two species were finally separated by 
Melvill (1919), and he correctly recorded M. 
ponderosum from Japanese waters. 

Through the good offices of Dr. Joel Greene of 
San Francisco, California, a mature, live-taken 
specimen of Morum exquisitum (figures E, F, J) 
was recently brought to my attention. This 
specimen, together with a dead one, was taken by 
divers in shallow depths off Laminusa, Sulu, 
Philippines. Now in the collection of the Ameri- 
can Museum of Natural History (cat. no. 183926), 

this specimen compares favorably in all details 
with the figured holotype, except it is slightly 
larger with 5 post-nuclear whorls, and has 12 ax- 
ial ribs on the body whorl. The apex is colored 
a pale pink, whereas the parietal shield and the 
blotches on the outer lip are a light purple-pink. 
Of the livmg species of Morum, it appears to be 
most closely related to the New World "twin 
species," M. veleroae Emerson, 1968, from the 
eastern Pacific, and to M. dennisoni (Reeve, 
1842), from the Western Atlantic. Attesting to 
the rarity of M. exquisitrim, I was able to locate 
only two other specimens in institutional collec- 

Compared to M. exquisitum, M. ponderosum 
(figures G, H, I) has a heavier shell, which is 
more triangular in outline, with coarser orna- 
mentation and a much lower spire. The parietal 
wall is heavily callused and the non-pustulose, 
flattened shield covers most of the apertural side 
of the body whorl. Numerous weakly formed, ir- 
regular folds extend down the perietal wall into 
the aperture. The outer lip is thickened and the 
inner margin is dentate; the lip extends poster- 
iorly to the penultimate whorl to form a deep 
sulcation. The shell, including the apex, is colored 
creamy white with occasional streaks and blotch- 
es of reddish brown, which are especially prom- 
inent on the reflected surface of the outer lip. 
The parietal shield is suffused with creamy tan 
and is variegated with reddish brown markings. 


July 1. 1977 

Vol. 91 (3) 

Perhaps one of the reasons Tryon (1885) erro- 
neously concluded that M. exquisitum and M. 
ponderosum were the same species was the result 
of the artist's lapsus in coloring the original 
figures (Hanley, 1858) of M. ponderosum reddish 

purple, instead of the natural reddish brown col- 
oration that is characteristic of this species. 

Morum praeclarum Melvill, 1919 was described 
from a unique specimen lacking locality data ob- 
tained from the collection of J. J. MacAndrew, 

FIGS. A-D Morum (0.) praeclarum MehnU; A-B Faqhuar Gniup. Seychelk hUimitt. in «/ m.. A' A/A// ho. 
71862. C-D Holotypc. MehnU-Tomlin OAl. NMW (Courtesy of Naiional Museum of Wales): A-D about 3A natural size. E. 
F, J Morum (0.) exquisitum (Adam.': & Reeve): Lattiimiita, Sulu Sen, Philippines, in li m.. AMNH No. }SS92(>: E, F about S/J, 
natural size: J spire greatly enlarged to show protoconch. G. H, I Morum (H.) pondero.sum (Hanley): Oeno Island. Pitcaim 
Islands, off reef. NMNH No. /.ilflOI: G, H about S/i natural size: I spire greatly enlarged to. ih/'upriitnrinirh. 

Vol. !)1 CA) 

July 1, 1!»77 


for whom Monim macandreui (Sowerby, 1889) 
had been named 30 years previously. Although 
the type specimen of M. praeclarum was il- 
lustrated recently in color (Dance, 1971), no addi- 
tional material had been recognized until 
Kilburn (1975) reported it from South Africa. Dr. 
Joseph Rosewater uncovered five specimens in 
the National Museum of Natural History collec- 
tions. An additional specimen was located in the 
Delaware Museum of Natural History by Dr. R. 
Tucker Abbott. These specimens were dredged by 
the "Anton Bruun". 

TVie newly discovered specimens of M. prae- 
clanini (figures A, B) are more diminutive than 
the holotype (figures C, D), the largest being 30.3 
mm in length, compared to 40 mm for the type 
specimen. Othenvise they agree well in essential 
characters with the description and illustrations 
of the holotype (Melvill, 1919; Dance, 1971). 
Melvill believed this species to be "nearest" to M. 
exquisitum, but he also compared it to M. macan- 
dreui. to which it is actually more closely 
related. It differs, however, from M. macandreui 
in several respects. The shell is smaller, propor- 
tionally more robust and less pyriform in out- 
line; the axial ridges are more delicate and they 
form sharp, scalelike spines at the intersections 
of the spiral ridges; the parietal shield is thickly 
enameled, finely ornamented with pustules an- 
teriorly and lineations posteriorly, and the den- 
ticles on the outer lip are confined to the aper- 
tural surface. Dance's illustration (1971, p. 119) 
suggests that the brownish spiral bands are well- 
developed on the holotype. In the present speci- 
mens, these bands are more diffused and are 
most prominent on the reflected surface of the 
outer lip and the adjoining portion of the body 
whorl. In these specimens, the surface is suffused 
in huffish cream and the spiral bands form 
streaks of light brown. As in the holotype, the 
aperture, outer lip, and parietal shield are a 
milky white. 


In a revision of the southwestern Pacific 
species, Beu (1976) reviewed the taxonomic status 
of the genus Morum Roding, 1798, type species by 
monotypy: Morum purpureum Roding, 1798 

{= St nimbus onisctis Linnaeus, 1767). In addition 
to the nominate subgenus, he recognized two 
subgenera: (1) Onisddia Morch, 1852, type species 
by monotypy: Onkcia cancellata Sowerby, 1824; 
(2) Herculea Hanley, in H. and A. Adams, 1858, 
type species by monotypy: Oniscia ponderosa 
Hanley, 1858. 

The attribution of the first valid use of 
Oniscidia to Morch, 1852, by action of the Inter- 
national Commission of Zoological Nomenclature 
(Opinion 1040), precludes the use of Cancel- 
lomorum Emerson and Old, 1963, type species by 
original designation: Oniscia grandis A. Adams, 
1855, and Onimusiro Kira, in Kuroda, Habe, and 
Oyama, 1971, with the same type species and 
method of designation. Both of these rejected 
taxa, which are currently widely used respective- 
ly in the American-European literature and in 
the Japanese literature, thus become junior sub- 
jective synonyms of Oniscidia Morch. Beu (1976) 
also referred Pulchroniscia Garrad, 1961, type 
species by monotypy: Pulchroniscia delecta Gar- 
rad, 1961 {^Oniscidia bruuni Powell, 1958, fide 
Beu, 1976), to the synonymy of Oniscidia Morch. 
Because generic synonymies of Morum sensu lata 
are given by Beu (1976), they are not repeated 


In addition to the three species discussed 
below, the following nominal species of Morum 
are known from the Indo-Pacific: M. (Oniscidia) 
cancellatum (G. B. Sowerby, I, 1824); M. (0.) 
grande (A. Adams, 1855); M. (0.) macandrewi (G. 
B. Sowerby, III, 1889; M. (0.) bruuni Powell, 
1958; M. (0.) teramachii Kuroda and Habe, in 
Habe, 1961; M. (0.) iwhiyjamai Kuroda and Habe, 
in Habe, 1961; and M. (0.) watsoni Dance and 
Emerson, 1967: quod vide for citations to the 
original descriptions. 

Morum (Oniscidia) exquisitum 

(Adams and Reeve, 1848) 

Figures E, F, J 

Oniscia exquisita Adams and Reeve, in Adams, 
1848, p. 35 [text p. 35, issued in May, 1850], pi. 
5, figs. 3a, 3b, [References To Plates, p. x and 
pi. 5, issued in November, 1848], "Sooloo [Sulu] 
Archipelago; outside a coral reef near the city 


July 1, 1977 

Vol. 91 (3) 

of Sooloo (Jolol in about sixteen to twenty 
fathoms, sandy mud." Reeve, 1849 [issued in 
August], vol. 5, Oniscia pi. 1, fig. 3, "Sooloo 
[Sulu] Archipelago" [repeats data of Adams 
and Reeve, 1850]. 
Oniscia exquisita Reeve, Kiister, 1857, p. 58, pi. 
55, fig. 10 (after Reeve, 1849, fig. 3), "Soulou- 
Archipel von Belcher entdeckt." 
Oniscia (OniscidiaJ exquisita Adams and Reeve, 
Tryon, 1885, p. 282, pi. 8, fig. 100 (after Reeve, 
1849, fig. 3), "Sooloo [Sulu] Sea; Australia." 
Morum (Oniscidia) exquisitum, Melvill, 1919, p. 
72, "Sooloo [Sulu] Archipelago [etc.], Philippine 
Isles (Hidalgo), Japan (Hirase), Saya de Malha 
Banks, S. Indian Ocean (J. Stanley Gardiner)." 
Morum exquisihim Adams and Reeve, Abbott, 
1962, p. 66, color illus., "Philippines, rare." 
Tifpe depository: not known (Melvill, 1919, p. 
72; Dance and Emerson, 1967, p. 95). The 
specimen figured by Reeve (1849), the apparent 
holotype, was sold in 1865 when the famous col- 
lection of John Dennison was disposed by public 
auction in London (Melvill, 1919; Dance, 1966, p. 
210). The holotypic specimen is apparently lost. 

Type locality: off Jolo [Sulu City], Sulu Island, 
Sulu Archipelago, Philippines, in 30 to 36 meters. 

Verified geographic range: Known only from 
the Sulu Archipelago, Philippines, in 6 to 36 

Material examined: Philippines: 6 meters, 
Laminusa, Sulu Archipelago, 1 specimen, 46.7 
mm in length, 27.4 mm in width, ex Joel Greene, 
AMNH 183926; Tawi-Tawi, Sulu Archipelago, 1 
specimen 30.3 mm in length, 19.5 mm in width, 
ex Mrs. P. Bautista, ANSP 218411, illustrated in 
Abbott (1962, p. 66); Zamboanga, Mindanao, 1 
specimen, 32.4 mm in length, 22.5 mm in width, 
NSMT .54630. 

Remarks: The early citations in the literature 
to records from Japan, Australia, and the Indian 
Ocean appear to be erroneous. Dr. Habe (personal 
communication) has no knowledge of specimens 
from Japanese waters. The specimen in the 
British Museum (Natural History) reported by 
Melvill (1919) from the Indian Ocean was sent to 
me on loan. It is apparently referable to Morum 
praeclarum Melvill, being a badly worn, broken 
and discolored juvenile shell. The Japanese and 
Australian records were based most likely on 

misidentified specimens of M. (H.) ponderosum. 
At the present time M. (0.) exquisitum is known 
only from the Sulu Sea. 

Oniscia exquisitum Adams and Reeve dates 
from November 1848, when the name was applied 
to figures 3a, 3b of plate 5 in the "References To 
Plates, Mollusca" of the Zoology of the Voyage of 
the H.M.S. Samarang. The description appeared 
subsequently, in May 1850, when the text was 

Morum (Oniscidia) praeclarum Melvill, 1919 

Figures A— D 

Morum praeclarum Melvill, 1919, p. 69, text fig. 

"Hab.[itat]?" J. J. MacAndrew Coll. Dance, 

1971, p. 119, fig. 5, "locality unkown"; 1975, 

Kilburn, p. 49, "off Mvoti River, 56 fms., and 

off Durban, South Africa, 160 fms." 

Type depository: holotype, here illustrated, 
figures C— D, Melvill-Tomlin Collection, National 
Museum of Wales, Cardiff (Dance and Emerson, 
1967, p. 95); N.M.W. accession No. 55.158, teste 
June Qiatfield. 

Type locality: 11 mi. off Port Shepstone, South 
Aft-ica in 2.50 fathoms. (Kilburn, 1975). 

Verified geographie range: western Indian 
Ocean; off Somali Republic and Mozambique, 
Africa; Seychelle Islands, in 78 to 132 meters off 
South Africa. 

Material examined: Africa; 80 miles E. of Ras 
Mabber, N.E. Somali Republic; 78-82 meters, 1 
specimen, 28.6 mm in length, 20.1 mm in width, 
"Anton Bruun," Sta. 9-445, 09°36' N. Lat.. 5r01 
E. Long., ex Harold Vokes, DMNH 117851; off 
Mozambique; ca. 40 miles E. Quissico, 132 meters, 
2 specimens, 30.3 mm in length, 21.1 mm in 
width, .30.1 mm in length, 19.1 mm in width, "An- 
ton Bruun," Cruise 7, Sta. 371-E, NMNH 761345. 
Seychelle Islands: ca. 80 meters, Faqhuar Group, 
1 specimen, 26.7 mm in length, 17.2 mm in width, 
"Anton Bruun" Cruise 9, Sta. 444, 09°36' N. Lat., 
5r01' E. Long., NMNH 718962; ca. 90 meters, Fa- 
qhuar Group, 2 specimens, 24.8 mm in length, 
17.2 mm in width, 2.3.2 mm in length, 16.4 mm in 
width. "Anton Bruun" Cruise 9, Sta. 437, 09°25' 
N. Lat., .50%54' E. Long., NMNH 718953. 

Remarks: At my request, Dr. June Chatfield 
kindly compared the holotype of M. pnurlannii 
with the illustration of the type specimen in 
Dance (1971, p. 119, fig. 5). She concluded that the 

Vol. 91 (3) 

Julv 1, 1977 


figure is fairly accurate in color, but it is perhaps 
a little darker than the holotypic specimen. The 
East African provenance of this species has been 
revealed through the dredging operations of the 
"Anton Bruun" in the Indian Ocean. Additional 
unrecognized specimens of this species probably 
exist in the extensive collections made in recent 
years from this region. 

Morum (Herculea) ponderosum (Hanley, 1858) 

Figures G. H, 1 

Oniscia ponderosa Hanley, 1858, pp. 255, 256, pi. 
42, fig. 9, 10, "Hab[itat]?," Cuming Coll. Tryon, 
1885, p. 282, pi. 10, fig. 22 (after Hanley, 1858, 
fig. 10), [incorrectly cited as a synonym 
of Morum exquisitum (Adams and Reeve)). 
Stearns and Pilsbry, 1895, "Yaeyama" [Ryukyu 
Islands], incorrectly cited as "Oniscia 
exquisita," which, following Tryon, was con- 
sidered to be a synonym of Morum pondero- 
Monim ponderosum (Hanley), Hirase and Taki, 
1951, pi. 98, fig. 2, "Amami-Oshima," Ryukyu 
Islands. Kuroda and Habe, 1952, p. 68, Range: 
0-29° North Latitude. Oyama and Takemura, 
1961, pt. 5, Morum pi. 2, figs. 4, 5, "Amami- 
Oshima Isl." 
Morum (Herculea) ponderosum (Hanley), H. and 
A. Adams, 1858, p. 621. Melvill, 1919, p. 71, 
"Japan (Steams)." Shikama, 1963, p. 59, pi. 42, 
fig. 4 "Amami-Oshima, Ryukyu Group, Japan." 
Habe, 1964, p. 69, p.. 21, fig. 1, "rare, Amami 
and Ryukyu Islands, wide-ranging in the Indo- 
Pacific regions." Shikama, 1964, p. 114, fig. 193. 
Ponder, in Beu, 1976, p. 224, "Herald Cay and 
Lady Elliot Island, Queensland." 
Type depository, Lectotype: BM(NH) No. 
1966724, ex Hugh Cuming Collection, selected by 
Dance and Einerson (1967, p. 94); syntype BM- 
(NH) No. 196625, ex Hugh Cuming Collection. 

Type locality; Amami-Oshima, Ryukyu Islands, 
here designated. 

Verified geographic range: Ryukyu Ar- 
chipelago, Japan; Queensland, Australia (fide 
Beu, 1976); New Caledonia; and the Pitcairn 

Material examined: Japan: Ryukyu Islands: 
"Oshima Osumi" [Amami-Oshima], 2 specimens, 

47.8 mm in length, 31.5 mm in width, 34.5 mm in 
length, 21.6 mm in width, Hirase Coll., NMNH 
34938; Amami-Oshima, 1 specimen, 31.7 mm in 
length, 21.8 mm in width, Hirase Coll., MCZ 
43262; Amami-Oshima, 2 specimens, 45 mm in 
length, 28.5 mm in width, 32 mm in length, 22.8 
mm in width, Hirase Coll., ANSP 98020; Amami- 
Oshima, 1 specimen, 22 mm in length, 18.2 mm in 
width, A. R. Cahn Coll., ANSP 275543; Okinawa, 
Onna sand flat, 1 specimen, 38.6 mm in length, 
26.7 mm in width, Bemice Albert, leg., ANSP 
276387; Okinawa, Kadena, 1 specimen, 36.6 mm 
in length, 24 mm in width, Rose Burch Coll., 
AMNH 114571; Okinawa, Kadena, 1 specemen, 
37.3 mm in length, 25.8 mm in width, W. A. Mc- 
Carty, leg., AMNH 183950. 

New Caledonia: 1 specimen, C. T. Trenchmann 
Coll., BM(NH) 1964504, teste A. F. Blake. 

Pitcairn Islands: off reef, N. coast of atoll, 
Oeno Island, 1 specimen, 41 mm in length, 27.8 
mm in width, H. A. Rehder leg., NMNH 731601: 
Henderson Island, 1 specimen, J. R. Jamieson and 
D. K. Tait leg., BM(NH) 1913.7.28.90, teste A. F. 

Remarks: According to Dr. Tadashige Habe 
(personal communication) sf)ecimens from the 
Hirase Collection bearing the locality Oshima 
Osumi are from Amami-Oshima of the Amami 
Group in the Ryukyu Archipelago. Early records 
attributed to "Japan" are actually referable to 
the Ryukyus and Okinawan Islands. The disjunct 
distribution of the uncommon species apparently 
represents gaps in collecting in the intermediate 
areas, rather than a relict distributional pattern. 


I am indebted to the following curators for pro- 
fessional courtesies of various kinds: Drs. R. 
Tucker Abbott, Delaware Museum of Natural 
History (DMNH); June Chatfield, National 
Museum of Wales (NMW); Kenneth J. Boss, 
Museum of Comparative Zoology, Harvard 
University (MCZ); George M. Davis, Academy of 
Natural Sciences of Philadelphia (ANSP); 
Tadashige Habe, National Science Museum, 
Tokyo (NSMT); Joseph Rosewater, National 
Museum of Natural History, Smithsonian Institu- 
tion (NMNH); and John Taylor and Miss A. F. 


Julv 1. 1977 

Vol. 91 (3) 

Blake, British Museum (Natural History) 
(BMNH). I thank my colleague, Mr. William E. 
Old, Jr., for technical assistance. 


Abbott, R. T. 196Z Sea shells of the World. Golden Press, New 

YorkieOp.. illus. 
Adams, Arthur. 1855. Descriptions of new genera and species 

of gasteropodous [sic] Mollusca. Proc. Zool. Soc. London 21: 

Adams, Arthur, and Lovell Reeve. 1848-.50. Mossusca. In A. 

Adams, The zoology of the voyage of H.M.S. Samarang; 

under the rommand of Captain Sir Edward Belcher. London 

(see Keen, 1971, p. 971, for dates of publication). 
Adams, Henry, and Arthur. 1853-,58. The genera of Recent 

Mollusca; arranged according to their organization. London, 

3vols.,661p., 138 pis. (dates of publication: vol. a p. 661). 
Beu. A. G. 1976. Revision of the southwest Pacific species of 

Manan {(Miscidia). Juur. Malac. Soc. Australia 3(4): 

Dance, S. P. 1966. Shell Collecting: an Illustrated History. 

Univ. Calif Press, Berkeley and Los Angeles, 344, p., 35 pis. 
Dance, S. P. 1971. Seashells. Hamlyn, London, 159 P., illus. 
Dance, S. P. and W. K. Emerson. 1967. Notes on Monim den- 

nisoni and related species. The Veliger 10(2): 91-98, pi. 12. 
Einerson. W. K. 1968. A new species of the gastropod genus 

Murum from the eastern Pacific. Jour, de Conchyl., 107(1): 

.5.3-.57,pl. 1. 
Emerson, W. K., and W. E. Old, Jr. 1963. Results of the 

Puritan-American Museum of Natural History Expedition 

to western Mexico. 19. The Recent Mollusks: Gastropoda, 

Strombacea, Tonnacea, and Cymatiacea. Amer. A/)is. 

Novitates, 21,53. .38 p., 28 figs. 
Garrard. T. A. 1961. Mollusca collected by M. V. "Challenger" 

off the coast of Australia. Jour. Malac. Soc. Australia 1(5): 

2-37, pi. 12. 
Habe, Tadashige. 1964. Shells of the Western Pacific in Color 

2. English ed., Hokusha, Osaka, Japan. 233 p. 
Hanley, Sylvanus. 18.58. Description of a new Oniscia. Pruc. 

Zool. Soc Londm 26: 2.5,5-256, pi. 42. 
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lustrated Shells, in Natural Cohrs. Tokyo, 134 pis. + 46.p. 
International Commission on Zoological Nomenclature. 1975. 

Opinion 1040, Oniscidia Mbrch, 1852 (Mollusca): Placed on 

the Official List. BuU. Zool Nomen. 32(3): 139-140. 

Kilbum. R.N. 1975. The rediscovery of Morum pmeclarum 

Melvill (Ca-ssidae). 77!eA«i((i7M.s89(2):49-.50. 
Keen, A. M. 1971. Sea Sheik of Tropical West America. Stan- 
ford Univ. Press, ed. 2, xiv + 1064 p.. illus. 
Kuroda, Tokubei, and Tadashige Habe. 1952. Checklist and 

Biblitiyraphy of the Recent Marine Mollusca of Japan, 

Tokyo, 210 p. 
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Shells <}fSayami Bay Collected by His .Majesty the Emperor 

of. Japan. Tokyo, 751 -(-489-1- 51 p., 121 pis. 
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Cabinet.Sd): 5.3-59; pi. 5.5. 
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with remarks on the Recent species of the genus. Proc. 

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Vol. 91 (3) 

July 1, 1977 



Helen DuShane' 

1M12 El Soneto Drive 
Whittier, California 90605 


Amaea siapnoi new species, a deepwater epitoniid, is described from a location 
about 540 nautical miles southwest of Mas Revillagigedo, Mexico. 

Species of Amaea are rare in the North Pacific 
Ocean. Until now, no species of this genus has 
been reported from the south eastern portion of 
the North Pacific Ocean. Recently, I have re- 
ceived, on loan, a live-collected specimen of a new 
species of Amaea s. s. for purposes of identifica- 
tion. Deepsea Ventures, Inc., May 1975, retrieved 
this mollusk from 14,521 feet (4428.60 meters), ap- 
proximately 540 nautical miles southwest of the 
Islas Revillagigedo, Mexico. 

Superfamily Epitoniacea 

Family Epitoniidae 

Genus Amaea H. and A. Adams, 1853 

[Type species (SD, deBoury, 1909: 

Scalaria magnifica Sowerby, 1844] 

Subgenus ylmoea H. and A. Adams, 1853 

Amaea (Amaea) siapnoi DuShane, n. sp. 

(Figs. 1 and 2) 

Shell medium in size, off-white in color; 
nuclear and early postnuclear whorls missing, six 
whorls remaining, gradually expanding to the 
last whorl; sides of the whorls more perpen- 
dicular than in most Amaea, giving it a columnar 
outline; suture well-defined; costae curved and 
retractive, lamellar near the distinct suture, worn 
on the whorls, not continuous from whorl to 
whorl; with a change of slope in the outline of 
the whorls just below the suture, causing the 
costae to curve rather abruptly; axial costae on 
the last whorl 85, of varying thickness, sometimes 
fusing with adjoining ones, continuous over the 

base to the simple lip (outer lip partially 
fragmented); with a poorly defined basal thread, 
below which the sculpture is the same as that 
above; spiral sculpture of approximately 16 to 22 
uneven but mostly extremely wide ribs, separated 
by narrow incised lines that cross the close-set 
axial costae and impart to the shell a somewhat 
beaded appearance; aperture round, lip thin; um- 
bilicus lacking; operculum dark, round, horny. 
Length 34 mm, width 12 mm (holotype). 

Type Locality— Approximsitely 540 nautical 
miles southwest of Isla Clarion, Islas 
Revillagigedo, Mexico (14°50' N, 124°29' W), from 
a depth of 4428.60 meters. 

' Museum Associate, Department of Malacology, Los Angeles 
County Museum of Natural History, Los Angeles, California 

FIG. 1. Map showing approximate location where Amaea 
(Amaea) siapnoi DuShane, n. sp. was taken in a dredge haul 
from a depth ofUJ,28.60 meters. 


July 1. 1977 

Vol. 91 (3) 

FIG. 2 Amaea (Amaea) siapnoi DuShane. n. sp. Left: Ven- 
tral view. Length 31, mm. uidth 12 mm. Center: Dorsal 
view. Right: Anterior portion enlarged to show poorly 
defined basal thread. X 2 

Type Material— Holotype, Department of 
Marine Invertebrates, San Diego Natural History 
Museum, San Diego, California: SDSNH 65482. 

Etymology— The species name honors the chief 
scientist of Deepsea Ventures, Inc., William Siap- 


Deepsea Ventures, Inc., working out of San 
Diego, California, is involved in exploratory min- 
ing for manganese nodules. William Siapno, chief 
scientist of Deepsea Ventures, Inc., collected this 
new species in May 1975. Other material in the 
dredge haul included coarse, gritty manganese 
that still adheres to the shell, manganese nodules, 
large Carcharodon teeth, pelagic shark teeth 
(probably of Miocene age), a whale ear-bone, 
small brittle stars, and worm tubes. 

The nuclear and immediate post-nuclear whorls 
of the holotype are missing. One can only conjec- 
ture that the live-taken specimen was damaged 
in the dredge as it was retrieved. 

Among the other Amaea collected in deep 
water are Amaea (Scalina) ferminiana (Dall, 
1908) from 118 to 1333 m off the coast of Peru by 
the SEPBOP Program on the vessel ANTON 
BRUUN (DuShane, 1974; 55); Amaea (Scalina) 
pompholyx (Dall, 1908) collected in 1485 m near 
the Galapagos Islands by the ALBATROSS (sta- 
tion 2807) in ooze (DuShane, 1974; 56). These are 

the only two records of Amaea (Scalina) from 
deep water in the tropical eastern Pacific; these 
depths do not approach the depth from which the 
present species was taken. Comparison with 
Amaea luxus Okutani, 1964, collected 56 miles off 
Aogashima Island (32° 20' N, 140° 55.5' E), in 
from 3,150 to 3,350 m, shows the two species to be 
congeneric, each with an usually large number of 
costae. The live-taken specimen of luxus differs 
by having 140 (instead of 84) close-set costae on 
the last whorl, a very elongate shell with 15 
whorls, and a hardly distinguishable basal disk. 


To the following people I am indebted in many 
ways; Drs. Myra Keen, Professor Emeritus, Stan- 
ford University and George Radwin, Department 
of Marine Invertebrates, San Diego Museum of 
Natural History, for reading preliminary drafts 
of the paper and providing constructive criticism; 
to Bertram Draper, Museum Associate, Los An- 
geles County Museum of Natural History, for the 
photographs; to Anthony D'Attilio, Department 
of Marine Invertebrates, San Diego Museum of 
Natural History, for the map; to William Siapno, 
Deepsea Ventures, Inc., and Dr. Hugh Bradner, 
University of California, San Diego, for their help 
in obtaining the holoptye for examination and 


Dall. W. H. 1890. Scientific results of exploration by the U. S. 
Fish Commission steamer ALBATROSS. VII. Preliminary 
report on the collection of Mollusca and Brachiopoda ob- 
tained in 1887-88. Proc. USNM 12(773): 219-362, pis. 5-14. (7 

deBoury, E. A. 1909. Catalogue des sous-genres des Scalidae. 
Jourii. de Conchyl. 57: 256-258. 

DuShane. Helen 1974. The Panamic-Galapagan Epitoniidae. 
The VeUger. Suppl. 16: 1-84, 154 photos, 1 map, 5 figs., 3 
tables. (31 May) 

Sowerby, G. B. (2nd) [\W1] 1847-1848. Thesaurus con- 
chyliorum, or monograph of genera of shells, edited by G. B. 
Sowerby, Jr.. completed by G. B. Sowerby 3rd. London, vol. 
1, part 4:83-146; pis. 32-40. (11 April) 

Vol. 91 (3) 

July 1, 1977 



Helen DuShane 

15012 El Soneto Drive, Whittier, California 90605 


Epitonmm (Asperiscala) textimattum DiiShane, n. sp. (Gastropoda,) in dencrihed 
from sublittoral water off the west Mexican states of Nayarit, Jalisco, and Colima. 
It resembles E. walkerianum Hertlein and Strong. 


Genus Epitonium Rbding, 1798 [Scala 

of authors; Scalaria Lamarck, 1801] 
Subgenus ylsperisca/a deBoury, 1909 

Species referable to the subgenus Asperiscala, 
with its type species of Scalaria bellastriata 
Carpenter, 1864, are relatively common consti- 
tuents of the Panamic-Galapagan fauna, there be- 
ing 21 recognized species. The new species is 
known only from the sublittoral zone, 7 to 18 
meters, in a mud substrate, dredged from 4 sta- 
tions off the states of Nayarit, Jalisco, and Co- 
lima, Mexico. 

Epitonium (Asperiscala) textimattum n. sp. 

(Figs. 1-8). 

Description: Shell medium to large in size, 
elongate-conic, white, sturdy; nuclear whorls .3 to 
4, horn-color, rounded, glassy, with a brown 
sutural line, first two whorls small, subsequent 
ones much larger and more bulbous with no 
noticeable sculpture; fifth whorl down with 
minute indentations and small axial ribs; post- 
nuclear whorls 5 to 10, rounded, slightly sloping; 
suture distinct; axial sculpture of 10 to 12 low, 
rounded, chinalike ribs, inverted V-shaped on 
early whorls, flat-topped and of varying widths 
on later whorls, with fine axial grooving and 
widely-spaced spiral sculpture on the sides 
(magnification of 20X), without angulation, curv- 
ing into the sutures, not continuous from whorl 
to whorl, with an occasional one twice the width 
of the others; channels between ribs twice the 
width of the ribs; axial and spiral sculpture 
striolate (magnification of 40X) between ribs, 
carr>'ing over the ribs as fine indentations; aper- 

ture ovate, outer lip but slightly thickened by the 
last rib, with faint traces of spiral impressions; 
peritreme complete, narrower on the columellar 
portion; umbilicus lacking; operculum light horn 
color, paucispiral. Length, 12 mm; width, 4 mm 

Discussion: This epitoniid from the Panamic- 
Galapagan fauna has an elongate-conic shape 
combined with a matte texture and sturdy ribs 
with faint, irregular spiral impressions. Sizes 
vary from 9.5 to 17 mm in length, with from 10 
tol2costae. (See Figs. 1,2,3) 

At first it was thought that this species might 
be the enigmatic Epitonium (Asperiscala) 
regulare (Carpenter, 1856), type locality, Panama. 
The original description of E. regulare mentions 3 
syntype specimens; Keen (1965) photographed 4 
specimens labeled with this name, but the label 
[BM(NH) Reg. No. 19.50. 4. 18. 13/16] is not in 

P'IGS. 1-3— Epitonium (Asperiscala) textimattum Lhi£hane. n. 
.■<p. l—Hiiliiti(pe (L.ACM. Mulnrnliigy Type Ciillectian. mi. 
ISi6). Length. 12 mm; uidth, I, mm. 2 and Z—Parat ifpes 
(LhiShane Collection). Smaller specimen: length, 11 mm: 
width, 5 mm. Larger specimen: length, 15.5 mm: width, 5 


Julv 1. 1977 

Vol. 91 (3) 

FIG. 4— Epitonium regulare (Carpenter. 1856): xyntype 
specimens. IBMlNH) Reg. No. 1950. I 18. 13/16]. The smallest 
.specimen in the phoUigraph. which may be the broken top of 
the Jii-st specimen to the left, has been lost fteste D>: John 
Taylor). Specimen to the far right was erronemisly considered 
by Palmer to he theholotype. X S.U 

Carpenter's handwriting (teste Keen). It is doubt- 
ful if any of the specimens shown (Fig. 4) are E. 
regulare of Carpenter, therefore, I do not choose 
to select a lectotype from among them. Compared 
to E. textimattum the left hand specimen has 
prominent sprial sculpture between the whorls 
and very thin costae. The smallest specimen from 
the left (lost, fide Dr. John Taylor, BM(NH)), 
might well be the upper broken portion of the 
lefthand specimen. The largest specimen has more 
convex whorls, a less contracted suture and twice 
the number of costae (20-22), with narrow in- 
terspaces between costae. The right hand 
specimen has many strong costae, crowded on the 
whorls, with fine spiral threads between. 

The brief description given by Carpenter (1856: 
164) makes identification of his nominal species 
difficult, if not impossible: therefore, their type 
status is questionable. Palmer (1963: 332) unwise- 
ly cited the last specimen mounted on the right 
as the holotype, which being figured by her, is 
tantamount to a type selection. This specimen 
does not fit Carpenter's original description. 
Because of the uncertainty of the identity of 
Carpenter's taxon it must stand as a species in- 

Pilsbry and Lowe (1932: 120) reported having 
taken Epiti>nium regulare at Acapulco, Mexico, 
but examination of the two specimens in the 
Lowe collection (SDMNH 26442), at San Diego, 
California, proves them to be Epitonium 
(Asperiscala) eutaenium Dall, 1917. Except for 
this one reference there seems to be no other cita- 

tions to E. regulare other than to the syntypic J 
specimens at the BM(NH). " 

Epitonium (Asperiscala) textimattum is closer 
to Epitonium (Asperiscala) walkerianum Hertlien 
and Strong, 1951 (3.7 to 8 mm in length), than to 
any other species in the Panamic— Galapagan 
fauna. It differs from the latter by having much 
finer spiral threads, fewer and discontinuous ribs, 
with an occasional heavier rib, and by having a 
larger shell (9.5 to 17 mm in length). The range 
for E. walkerianum is from San Felipe. Gulf of 
California, along the west coast of Mexico as far 
south as Nicaragua, taken from the intertidal 
zone down to 23 meters, whereas E. textimattum 
is known only from off the west Mexican states 
of Nayarit, Jalisco, and Colima. 

The soft parts, when live, show through the 
shell as coral-pink in color. The color fades to a 
peach-tan within a few weeks. Sixty specimens of 
this species were dredged just beyond the wave 
line at Playa Los Angeles, Jalisco. Mexico, mud 
substrate, at a depth of 7 to 18 meters in associa- 
tion with the sand dollars, Encope firagilis Clark, 
1948 and Encope perspective Agassiz, 1841, 
August 1975, by Carol and Paul Skoglund. Dredg- 
ing repeated at the same locality in December, 
1975 revealed only two specimens of the new 
species and only a few specimens of Persicula sp. 
and Kurtziella sp. that were so numerous in 



lO*' SO' 

FIG. 5-Mn/) taken from the U. S. Hydrographic Siitfey 
showing the coastline along which Epitonium (.\.speriseala) 
textimattum IhiShane. n. sp. occurs. Tlie .tolid triangle in- 
dicates the type locality. 

Vol. 91 (3) 

July 1, 1977 


FIG. 6— Epitonium (Asperiscala) textimattum IkiShane n. sp. 
Niuclear whorls showing sculpture on the fifth whorl down of 
minute indentations and small axial ribs (white portions). 

August. In addition, few sand dollars were pre- 
sent in the December dredgings. 

Type locality— Play a. Los Angeles, Tenacatita 
Bay, Jalisco, Mexico (Lat. 19° 18' N; Long. 104°50' 
W). at depths of 7 to 18 meters. (See Map) 

Type material— hohtype, Los Angeles County 
Museum, Malacology Type Collection, No. 846. 
Paratypes (1): To each of the following institu- 
tions, American Museum of Natural History, 
British Museum (Natural History), Delaware 
Museum of Natural History, Los Angeles County 
Museum of Natural History, National Museum of 
Natural History (Smithsonian Institution), 
Academy of Sciences of Philadelphia, Santa Bar- 
bara Natural History Museum, San Diego Na- 
tural History Museum; (2) DuShane Collection; 
remainder in the Bennet and Skoglund Collec- 
tions. Additonal paratypes.— Lo de Marcos, Na- 
yarit; collected by the Bennets and Skoglunds, 
September, 1974, dredged from 7 to 18 m, 1 
specimen; Cuastecomate, Jalisco; collected by the 
Skoglunds, August, 1975, dredged from 11 to 27 

FIGS. 7 and 8— Epitonium (.'\speriscala) textimattum 
DuShane, n. sp. 7— Operculum showing growth lines. Actual 
size 2 mm. %— Attachment side of operculum showing 
muscle attachment scar. 

m, 2 specimens; Santiago Bay, Colima; collected 
by the Skoglunds, August, 1975, dredged from 11 
to 18 m, 1 specimen. 


To Dr. William K. Emerson I am most in- 
debted for having read the manuscript and of- 
fered useful suggestions and corrections, as well 
as the species name; to Dr. George E. Radwin for 
the loan of two specimens form the Lowe Collec- 
tions; to Dr. Myra Keen for her photograph of 
syntypic specimens of E. regulare in the BM(NH) 
and to Bertram Draper for photographs of the 
new species; to Dr. John Taylor for comparison of 
species involved; to Merton Goldsmith for the 
drawings and the map; to the Skoglunds (Carol 
and Paul) for the privilege of naming this new 


Carpenter, Philip Pearsal. 1856. Description of new species of 
shells collected by Mr. T. Bridges in the Bay of Panama and 
its vicinity, in the collection of Hugh Cuming. Esq. Proc. 
Zool. Soc. London. 159-166 (for 1856), (9 June) 

Carpenter. Philip Pearsal. 1864. Supplementary report on the 
present state of our knowledge with regard to the Mollusca 
of the west coast of North America. Brit. Assoc. Adv. Sci.. 
Report. 33 (for 1863): 517-686 (post 1 August) [reprinted in 
Carpenter. 1872: 1-172 (dating: Carpenter. 1872)1 

Clark, Hubert Lyman. 1948. A report on the Echini of the 
warmer eastern Pacific, based on the collection of the 
Velero III. Allan Hancock Pacific Expeditions, Univer. So. 
Calif Press. 8(5): 1-352. pits. 35-71, text figs. 1-3. 

deBoury, Eugene Auborg. 1919. Catalogue des sous-genres des 
Scaladea. Jo!(n!. de Conchyl. 57: 256-258. 

DuShane. Helen. 1974. The Panamic-Galapagan Epitoniidae. 
The Veliger. Suppl. 16: 1-84; 1.54 photos. 1 map, 5 figs. (31 
May 1974) 

Hertlein, Leo George and Archibald McClure Strong. 1951. 
Eastern Pacific expeditions of the New York Zoological 
Society. Mollusks from the west coast of Mexico and Central 
America. Part X. Zoologica 36: 67-120; pits. 1-11 (20 August 

Palmer. Katherine V. W. 1963. Type specimens of marine 
mollusca described by P. P. Carpenter from the west coast 
of Mexico and Panama. Bull. Amer Paleo. 46(211):285-408; 
pits. 58-70 (22 October 1963) 

Pilsbry, Henry Augustus and Herbert N. Lowe. 1932. West 
American and Central American mollusks collected by H. 
N. Lowe. 1929-31. Proc. Acad. Nat. Sci. Philadelphia 84: 
33-144; 7 figs.; pits. 1-17; 2 photogr. (21 May 1932). 


July 1, 1977 

Vol. 91 (3) 


Craig M. Doremus and Willard N. Harman 

Biology Department 

The State University of New York 

College at Oneonta 13820 


Populations of Physa heterostropha (Say) (Physidae) and Promenetus exacuous 
(Say) (Planorbidae), were used in two-week experiments in controlled laboratory 
microeconystems. Comparison of cholorphyll extracts from periphyton in snail-less 
aquaria unth those containing snails were used to determine relative grazing effi- 
ciency. Snail population density was inversely correlated with periphyton standing 
crop in all sitautions, except for pure cultures of?, exacuous. 

Studies of this kind have application in natural areas where decimation of snail 
populations has effects on the species composition of the algal flora, and therefore, 
water quality and resource utilization. 

The effects of grazing by snails and other 
aquatic invertebrates on periphyton (benthic 
algae) is poorly known. Logically, one would ex- 
pect the standing crop of periphyton to decrease 
in the presence of grazing invertebrate popula- 
tions. Indeed, Douglas (1958) suggested that the 
caddis fly larvae, Agapetus fuscipes, controlled 
the population size of the diatom Achanthes dur- 
ing the spring and summer in a small stream in 
England. She noted a strong inverse relationship 
between the numbers of the caddis fly larvae and 
numbers of diatoms during that time. A study 
along the Oregon coast by Castenholtz, (1960) 
demonstrated how a heavy diatom population in 
the upper half of the intertidal zone was held in 
check by limpets and littorines during summer 
periods. Kehde and Wilhm (1972) noted how snail 
grazing affected the community structure of 
periphyton in labortory streams. They exposed 
the periphyton to grazing by the snail Physa 
gyrina Say for three months and measured a 
significant increase in the chlorophyll a concen- 
tration and a slight reduction in the standing 
crop of the periphyton. Beyers, (1963) in a 
laboratory microecosystem, showed that when the 
large herbivorous snail Marisa comuarietis 
(Linne) was added to the system, it severely 
overgrazed the macrophytes and associated 

The following pilot study was undertaken to 
determine: (1) the effect that selected freshwater 
pulmonate snails have on periphyton standing 
crop, (2) the effects the population density of 
these snails has on the grazing ability of in- 
dividuals, and (3) whether one species has effects 
on the other's grazing ability when both are in 
the same laboratory microecosystem. 


Individuals of Physa heterostropha (Say) about 
13 mm. in length and with an average wet weight 
of .06 gm. and those of Promenetus exacuous 
(Say) about 4.5 mm. in length and with an 
average wet weight of .01 gm. were used for the 
experiment. Both species are commonly found in 
central New York State (Harman and Berg, 
1971). The individuals used for the study were 
taken from coexisting populations in Rat Cove, a 
partially protected bay along the southwestern 
shore of Otsego Lake, the headwaters of the Sus- 
quehanna River in east-central New York. The 
lake is morphometrically oligotrophic but 
chemical characteristics are typical of eutrophic 
waters. It has a surface area of 1,725 ha (6.7 sq. 
miles) and a maximum depth of 51 m (166 ft.). 
Rat Cove has a littoral area roughly .4 x .2 km. 
in size, up to 6 m. in depth and has a bottom 

Vol. 91 (3) 

July 1. 1977 


TABLE 1. Oiaracteristics of gastropod populations, algal populations and water utilizedfor the study. 

Number of snails 



weight of 







Physical and Chemical Parameters 

P heter- P 
imtrnpha exanious 




0, cone 






Rat Cove 

10- r 
















































* estimates per unit area equal to one laboratory microecosystem. 

composed of deep organic muds (Herrmann and 
Harman, 1975). 

Laboratory microecosystems were set up in 
twenty-nine covered, rectangular plastic "mini- 
tanks" (18 X 25 X 10 cm). Each was sterilized with 
95% ethanol and then rinsed thoroughly with tap 
water. Three liters of lake water from Rat Cove, 
filtered through a screen with a .5 mm filter 
mesh to remove macroinvertebrate grazers, were 
added to each tank to provide a potential snail 
grazing surface area of 1250 cm^ Three 
microscope slides, each with a surface area of 19 
cm^ were placed in each container. Various 
population densities of snails (Table 1) were used, 
some with one species present and others with 
both species coexisting. A density of 10 in- 
dividuals of Physa and 4 individuals of Pro- 
menetus was considered an estimation of the 
population density of each respective snail 
population in Rat Cove. With this as a basis, we 
arrived at the densities shown in Table 1 by 
lowering or increasing the number of snails per 
tank proportionally. The complete series was 
duplicated and the control (no snails in a con- 
tainer) was repeated three times. 

Aquaria were arranged in rows 25 cm below 
continuously illuminated 20 watt naturescent and 
gro-lux fluorescent lights. Each tank was fur- 
nished with continuous aeration. Half the water 
was removed twice a week from each container 

and replenished with filtered lake water to pro- 
vide a regular turnover of nutrients. At these 
times dead snails were replaced with living in- 
dividuals from Rat Cove. 

To ascertain if conditions varied among the 
tanks and between natural and laboratory condi- 
tions, various chemical and physical charac- 
teristics of the water were determined in each 
aquaria and the snail collection site in Rat Cove. 
Water was analyzed for pH using a Beckman pH 
meter. Dissolved oxygen determinations (mg/1) 
employed the Winkler method-azide modification 
(APHA et al, 1970). Total alkalinity (as CaCo, in 
mg/1) was determined by titration with .02N 
H2SO4 using methyl orange as an indicator 
(APHA et al, 1970). Temperature and dissolved 
oxygen were utilized to determine oxygen satura- 
tion from a nomograph (Hutchinson, 1957). Dis- 
solved solids were determined by a Myron Dis- 
solved Solids Meter. 

Snails were allowed to graze two weeks in the 
tanks. At the end of that time all slides were 
removed. The three slides from each aquaria were 
collectively placed in flasks with 200 ml of 90% 
acetone for 72 hrs. at 5° C to extract chlorophyll. 
In a 2.54 cm spectrophotometer cell, chlorophyll 
transmittance was read at the 665 mn setting of 
a Bauch & Lomb (Spectronic 20) spectrophoto- 
meter. Results, expressed as a percentage of the 


July 1, 1977 

Vol. 91 (3) 

transmittance exhibited by the chlorophyll ex- 
tracted from the controls, were utilized as 
measurements of the standing crop of periphyton. 
Thus, low values indicated that periphyton 
populations were greatly reduced by grazing 
snails. We consider these to represent efficient 
grazing abilities. The ^ig of chlorophyll a per m' 
was also utilized for comparative purposes 
because it is a potentially more definitive index. 
The results are given as fig Chi a/m' = 937.01 
(Optical Density at 665 m/i), which assumes the 
absence of degredation products and interfering 
pigments in the chlorophyll extract. 

There was a significant size and weight dif- 
ference between specimens of Physa (.06 gm/in- 
dividual) and those of Promenetus (.01 gm/in- 
dividual). In order to give an accurate picture of 
the relative grazing abilities of the two species, 
total weight of the populations were used as a 
measure of population density. Since individuals 
of P. heterostropha weighed six times more than 
those of P. exacuous, it was assumed that six 
individuals of P. exaciunis would have grazing 
abilities comparable to one individual of P. 


Limnological characteristics of the tanks con- 
taining Physa are illustrated in Table 1 as are 

characteristics of aquaria supporting populations 
of Promenetus and limnological features of tanks 
containing populations of both species. Also il- 
lustrated are physical and chemical characteris- 
tics of the water in Rat Cove at the time the 
snails were initially collected on August 4, 1974. 

The chemical and physical characteristics of 
the tanks containing P. heterostropha tend to ex- 
hibit reduced values as population density in- 
creases, except for oxygen saturation and the 
related parameters of temperature and oxygen 
concentration. All values peaked at intermediate 
population densities when only Promenetus was 
present. When the two species coexisted, the 
values appeared to remain stable as density in- 
creased. A series of t-tests indicated that signifi- 
cant differences between aquaria occurred in 
alkalinity and dissolved solids despite continual 
addition of lake water. All statistical analyses 
were performed at the 0.05 level. 

Water from Rat Cove and in the experimental 
aquaria differed greatly. Both environments were 
provided with the same amount of nutrients, but 
the tanks were completely enclosed and exhibited 
the characteristics of high eutrophy in a short 
time under continuous illumination. This is ap- 
parently related to the great surface area per 
unit substrate in Rat Cove that absorbs the 
nutrients, only slowly releasing them, compared 


Promenetus exacuoui 
Physa heterostropha 
Both species coexrsting 

.4 5 .6 

Total snail weight per crisper 

FIG. 1. (ir(uing€fficie7Uiy of maik expressed as Log (Ckl a ^igrns/m^) ^ 2.550 - .297 Log (total snail weight per crisper). 

Vol. 91 (3) 

July 1, 1977 


tx) their immediate availability in the tanks. The 
result is a buffering of the eutrophication process 
in Otsego Lake when enrichment is not too 

Limnological parameters measured in each 
container were well within the limits for the two 
species measured by Harman and Berg (1971) in 
their survey of freshwater snails of central New 
York, indicating that the chemical conditions in 
the tanks were not atypical and the results can 
be applied to natural populations. 


Table 1 indicates the grazing efficiency of both 
mixed and pure cultures of P. heterostropha and 
P. exaxnious. The grazing efficiency of all snail 
populations was represented by the equation (Log 
Y = 2.550 - .297 Log X) where Y equals the 
chlorophyll a content in ^gm/m^ (extracted from 
slides placed in the aquaria) and X equals the 
total snail weight per tank, a measure of snail 
population density. The negative correlation, 
shown in Figure 1, clearly illustrates the fact 
that as snail population density increased, stand- 
ing crop of periphyton (chlorophyll a content) 

Physa heterostropha had a grazing ability effi- 
cient enough to reduce the standing crop of 
periphyton at all population densities studied 
(Fig. 1). The positive correlation between popula- 
tion density of P. exacuous and periphyton 
chlorophyll concentration illustrates the fact that 
this species is unable to limit growth of algae 
(Fig. 1). The increase in periphyton population 
density writh increase in snail population density 
may be due to the increased availability of nu- 
trients brought about by the presence of snails in 
the crispers. However, equally possible are effects 
of competitive interactions between algal species 
resulting from differences in the grazing char- 
acteristics of the snail species involved. 

The grazing ability of coexisting snail popula- 
tions is not significantly different from that of 
pure cultures of P. heterostropha (Fig. 1). This is 
what was expected, since P. exacuous added very 
little biomass in the experiments utilizing coex- 
isting populations. 

The sides and bottom of the snail-less control 
tanks were thickly covered with attached algae, 

but those with snails in them appeared relatively 


It is an overgeneralization to state that 
periphyton standing crop is decreased by the 
presence of snail populations. Although this is 
often the case, as shown by our data collected 
form pure cultures of P. heterostropha and mixed 
cultures of P. heterostropha and P. exacuous, 
situations can arise when algal standing crops in- 
crease in size. 

When a particular species of gastropod grazes 
it undoubtedly alters competitive interactions 
between various species of algae by more effi- 
ciently cropping one species than another. In a 
natural environment these alterations could be 
extremely significant. In this study it was not 
determined whether this kind of phenomenon 
caused the periphyton standing crop to increase 
as the population density of P. exanwus in- 
creased. These results may have come about 
because of "inefficient" grazing of P. exacuous, in 
combination with the effects of continuous il- 
lumination and added nutrients associated with 
the presence of the snails. 

In many localities great effort has been ex- 
pended on the eradication of freshwater snail 
populations because they are intermediate hosts 
of economically important trematode parasites. 
The harvesting of rooted aquatic plants, with con- 
comittant removal of gastropods, is taking place 
in more and more situations where the plants 
have become nuisances. If snails have important 
effects on the standing crops of benthic algae in 
those ecosystems, studies such as this could deter- 
mine how well snails control algal population 
densities, and therefore, maintain the quality of 
natural waters. 


APHA, AWWA, and WPCF. 1970 Standard metehods for 
the examination of water and wastewater. American Public 
Health Association. 

Beyers, R. J. 1963. The metabolism of twelve aquatic 
laboratory microecosystems. EcnI. Monagr. 33:281-.306. 

Castenholts. R. W. 1961. The effect of grazing on marine lit- 
toral diatom populations. Ecology A2(i): 783-794. 


July 1. 1977 

Vol. 91 (3) 

Douglas. Barbara. 1958. The ecology of the attached diatoms 
and other algae in a small stony stream. J. EcoL 46: 

Harman. W. N. and C. 0. Berg. 1971. Tlie freshwater snails of 
central New York with illustrated keys to the genera and 
species. Search: Cornell Univ. Agr. Exp. Sta., Eiitomol., 
Ithaca my. 1-68. 

Herrman. S. A. and W. N. Harman. 1975. Studies on two 

populations of Physa heterostropha (Say). Ohio J. Sci. 75(2): 

Hutchinson, G. E. 1957. A treatise on limnology. Volume 1. 

John Wiley and Sons. Inc. 
Kehde, P. M. and J. L. Wilhm. 1972. The effects of grazing by 

snails on community structure in laboratory streams. 

Amer. Mid. Nat. %7 {I): S-2i. 



Ralph W. Dexter 

Department of Biology 
Kent State University, Kent, Ohio 44242 

At the 1965 meeting of the American Mala- 
cological Union, I challenged the conclusions of E. 
S. Morse who published various reports from 1879 
to 1925 showing differences in the proportion 
(length-width) of bivalve shells between those 
found in native shell-heaps and living sjjecimens 
from the same locality. He believed that the dif- 
ference was due to climatic change. However, it 
was demonstrated that the ratio of Mya arenaria 
L. depends upon the nature of the substratum in 
which the clams developed. Without a knowledge 
of the substratum, comparisons cannot by made 
{Annual Reports, A.M.U. for 1965, p. 18). 

In studying the correspondence of naturalists 
at the Museum of Science, Boston, Massachusetts, 
I encountered a similar situation. Apparently, 
Sameul H. Scudder, Curator at the Boston Society 
of Natural History, believed he could detect a dif- 
ference in shell size between fossil and recent 
shells of the quahog (Mercenaria mercenana L.) 
and, like Morse, had assumed an evolutionary 
change. Addison E. Verrill, at Yale University, 
however, realized the differences could be due to 
local environmental conditions. He wrote to Scud- 
der 9 October 1875 as follows: 

"You are perfectly correct in regard 
to the peculiarities of the majority of 
the fossil quahogs with the average 
specimens seen in our markets. I had 
noted the same differences, but they 

are not constant in the fossils, for in 
my lot there are some of good size that 
are as thin and smooth as ordinary 
New Haven specimens of the same size 
and they have the same form also. We 
have a large number (50 or more) of 
good, large (3-4'/2 in.) Nantucket 
quahogs obtained from a native. They 
are remarkable for their massiveness, 
for their strong concentric rings and 
most of them are rather rounded and 
the disk violet color extends in a broad 
zone entirely across the shell (the 
same is true of some of the fossils that 
retain traces of color), and in the 
totality of their characters they are 
more like the average fossil quahogs 
than are those from any other locality 
yet examined, but in the same lot are 
some of the thin, elongated ones nearly 
smooth in the middle like the ordinary 
sort and others that are intermediate. 
I imagine that such differences as oc- 
cur are due to local causes and were in 
ancient times as now, inconstant. I 
presume that localities might now be 
found where the quahog would be 
precisely like the fossils." 
Permission to quote Verrill's letter was kindly 
given by the Museum of Science, Boston, Mass. 

Vol. 91 (3) 

July 1, 1977 



Kathleen A. Burky' and Albert J. Burky' 

Instituto de Zoologi'a Tropical, Facultad de Ciencias, 
Universidad Central de Venezuela, Caracas, Venezuela 


The ampullariid Pomacea urceus uses its ctenidium and lung in respiration. The 
snails reach the surface urith their siphon and ventilate their lung by urithdraunruj 
their head-foot in a pumping action. The lung gas also serves to change the 
buoyancy of the snails. After a ventilation a snail does not necessarily return to 
the same hioyancy level. They may achieve overall specific gravities of <1 to >1 
after a ventilation. They may remain submerged (s.g. >1) or float (s.g. <1) for long 
periods. In the field many P. urceus are found floating during periods of low ox- 
ygen tension. Underwater weights were recorded over 2h hr and five day periods. 
Weight changes are representative of gas volume changes in the lung. The most 
rapid changes take place over the first six hours. Adult snails normally ventilate 
their lung within the first two hours of submersion. Juvenile P. urceus ventilate 
their lung more frequently than adults. Pomacea falconensis and P. luteostoma are 
similar to juveniles of P. urceus in size and show similar ventilation rates. The 
rate differences probably reflect the difference in lung capacity to total tissue in 
relation to metabolic rate. 

Considerable significance attaches to any obser- 
vations on the structural and functional adapta- 
tions shown by "primitive" lung-fish. This is also 
true for amphibious snails. Such observations, 
especially physiological data from whole animals, 
can be of interest in two ways. First, at the level 
of mechanistic physiology, they help establish our 
concepts of how such an "unlikely" animal ma- 
chine as one built on the basic molluscan plan — 
of great efficiency in an aquatic environment — 
can maintain itself on land. Secondly, it is possi- 
ble that hypotheses on the evolution of the major 
land stocks can be modified as a result of phy- 
siological investigation of amphibious stocks 
(whether they involve "partially adapted" or 
"doubly adapted" forms). 

The remarkable physiological plasticity shown 
by amphibious and freshwater snails of the major 
class Pulmonata has been discussed elsewhere 
(Russell-Hunter, 1964). The mantle-cavity con- 
verted as a "lung" can be used in rhythmic "div- 

' Present address: Department of Biology, University of 
Dayton, Dayton Ohio 4&J69, U.S.A 

ing" (Russell-Hunter, 1953a, b, 1957), or be 
water-filled, or have its gas used as a "physical 
gill" for the underwater uptake of oxygen (Rus- 
sell-Hunter, 1953b; Henderson, 1963), or prin- 
cipally to provide buoyancy (Jacobs, 1941; Rus- 
sell-Hunter, 1953b; Henderson, 1963). 

Among the amphibious prosobranchs are sever- 
al genera and species in the family Ampulla- 
riidae (superfamily Viviparacea). It has long 
been known (Troschel, 1845; Pelseneer, 1895) that 
ampullariid snails possess unusually "amphib- 
ious" respiratory structures, one part of the 
mantle-cavity containing a ctenidium and ano- 
ther part being modified as a gas-filled lung cavi- 
ty. Significant anatomical studies on ampul- 
lariids have been reviewed (FYetter and Graham, 
1962; Demian, 1965; Andrews, 1965a, b) and the 
physiology of aestivation has received attention 
(Meenakshi. 1956. 1957, 1964; Visser. 1965; 
Burky. Pacheco. and Pereyra, 1972). The behavior 
of lung ventilation has been discussed by Robson 
(1922). Prashad (1925, 1932), and Andrews (1965b), 
and examined in greater detail by McClary (1964) 
and Demain (1%5). Until recently there has been 


Julv 1, 1977 

Vol. 91 (3) 

little modern physiological and ecological work 
on populations of ampullariids, but now there are 
extensive data on Fomacea urceits. which is abun- 
dant over vast areas of the Venezuelan savannah. 
These include data on growth and biomass turn- 
over (Burky, 1973, 1974) and on temperature, wa- 
ter, and respiratory regimes (Burky, Pacheco, 
and Pereyra, 1972). This paper reports work on 
buoyancy changes in relation to respiratory be- 
havior in Pomacea urceus (conducted by the 
senior author in Venezuela in 1970, along with 
some comparative notes on other aspects of respi- 
ration in P. urreua, and with limited comparative 
data on three other species of ampullariids. 


The snails were initially maintained in large 
outside tanks and then moved to aquaria in the 
laboratory. Caracas tap water was used but only 
after it had been allowed to stand for 24 hr or 
longer. When changing the water (at least twice 
a week), 25%-50% of the used "conditioned" 
water was usually retained. Snails were regularly 
fed lettuce. 

The weighing apparatus used in this investiga- 
tion (Fig. 1) was designed after that used by 



FIG. 1. Weiyhiny apparatus. 

Henderson (1963). A triple-beam balance and a 
plastic weighing cage (made from a two liter bot- 
tle) with a volume of about 1.25 I were used. 
Lead weights were added to the naturally buoy- 
ant plastic cages until an underwater weight of 
9-10 g was reached and this weight is referred to 
as the zero weight. This could easily ac- 
commodate the range of buoyancy changes in P. 
urceus. When the underwater weight of a snail is 
greater than the zero weight, it has an overall 
specific gravity of greater than one. It follows 
that underwater weights of less than or equal to 
the zero weight will correspond to specific 
gravities of less than one and one respectively. 
Snails were taken from aquaria at ambient room 
temperature (about 20-25° C) and placed in cons- 
tant temperature tanks (maintained near 29° C) 
two days before each experiment. Eighteen to 24 
hr before an experiment, a snail was placed in an 
experimental cage with lettuce. The cage was 
suspended from the balance by coated copper 
wire a few centimeters below the water surface. 
On the morning of each experiment uneaten let- 
tuce was removed and the snail was observed un- 
til it ventilated its lung by reaching the surface 
with its siphon. It was immediately lowered to a 
depth of more than double its shell length so it 
could not reach the surface with its siphon to 
ventilate, and weighed. Subsequent weighings 
were made at various intervals depending on the 
experiment. The water was continuously aerated 
throughout each experiment; all snails were 
starved throughout each experiment; and all ex- 
perimental temperatures were in the range of 
28.75-29.75° C, since this is near the natural field 
temperature during the rainy season (Table 1). 

The weight of a snail is reduced by a force 
equal to the mass of the water displaced when 
submerged. The submerged weight reduction in 
grams (without gas in the lung) is equal to the 
volume of water displaced (milliters), since one 
gram of water can be assumed to have a volume 
of one milliliter. It follows that the weight of a 
submerged snail will be further reduced by one 
gram per milliliter of gas (weight of the gas is 
disregarded) in the lung. Therefore underwater 
weight changes give an accurate picture of the 
gas volume changes in the lung. Since milliliters 

Vol. 91 (3) 

July 1. 1977 


TABLE 1. Physical data from the natural habitat of 
Pomacea urceusduhng the rainy season. 





0, ppm 



Bottom Surface 
Water Water 


11 Aug. 70 


29.2 30.1 





29.4 30.4 





29.6 31.5 





30.0 32.8 





31.2 31.5 





30.4 30.5 





30.2 30.3 





30.2 29.8 




12 Aug. 70 


29.7 29.6 





29.5 29.4 





29.2 29.1 





29.0 28.8 





28.8 28.6 




and grams are equivalent, the gas in the lung at 
the start of each exi)eriment can be estimated. 
The volume of a contracted snail in milliliters 
(determined by displacement of water) was sub- 
tracted from the weight of the snail (in air) in 
grams to give the underwater weight of the snail 
without any gas in the lung. It follows that the 
difference between the underwater weight with- 
out gas and the underwater weight of the snail 
immediately after ventilation will give the mil- 
liliters of air present in the lung. It is necessary 
to estimate the initial gas volume since it is not 
possible to force these snails to expel all gas for 
an underwater weight (without gas) at the end of 
an experiment. It also follows that the volume 
meaurement of a snail is not accurate and will 
include the volume of any retained gas. There- 
fore, initial gas volumes are underestimates but 
make reasonable comparisons between snails pos- 

Observations on the interval between successive 
ventilations and the number of pumps per ven- 
tilation were made on adults and juveniles of 
Pomacea urceus, and on adults of P. falconensis 
and P. luteostoma (Swainson). Some general 
observations were also made on Marisa cor- 
nuarietis (Linne). 

Field measurments were taken hourly over a 
24 hr period. Temperatures were recorded with a 
YSI Tele-thermometer; oxygen tensions were re- 
corded with a YSI portable oxygen electrode; and 

pH values were recorded with a portable pH 


It is important to know the weight and volume 
of body parts for Pomacea urceus. This informa- 
tion is partly based on the data of Burky, 
Pacheco, and Pereyra (1972) and is given for a 
hypothetical snail of lOOg in Table 2. 

Volume reductions over twenty-four hours of 
submersion— Ohservsitions of underwater weight 
changes were made over 24 hr periods of contin- 
uous submersion. Periods of submersion started 
immediately after ventilation of the lung. Under 
experimental conditions a snail usually reduces 
its overall specific gravity without becoming 
buoyant. The results of such an experiment are 
illustrated in Fig. 2 and given in Table 3. 

The weight increases (volume reductions) are 
brought about smoothly with time. The most 
rapid changes take place during the first six 
hours. The weight increase in the first hour is 
equivalent to a 6.7% reduction in the volume of 
gas. The rate decreases to Ll% of the initial 
volume in the sixth hour. In the first six hours, 

TABLE 2. Estimated weight and volume of body parts for a 
hypothetical snail with a maximum live weight of 100 g (shell 
length, abotit 85 mm). 

_ <mlr 
Without gas 
Body part and condition g' volume of 


Whole live active snail (includes shell) 

Water retained in mantle cavity 

Wet tissue of active snail 

Dry tissue of active snail 

Whole live aestivating snail at end 

of dry season (includes shell) 
Wet tissue of aestivating snail at end 

of dry season 
Dry tissue of aestivating snail at end 

of dry season 

* The above values are based on weights from 59 active and 
15 aestivating snails, and from the extensive data on the rate 
of weight loss during aestivation (Burky, Pacheco, and 
Pereyra. 1972). The shell volume is based on a compromise 
specific gravity (2.8) between calcite and aragonite since the 
crystalline structure is not known. Also, the shell contains 
organic compounds. It is assumed that the specific gravity of 
wet tissue is 1.0. 

















July 1. 1977 

Vol. 91 (3) 

Tim* (hours) 

FIG. 2. Underwater weight changes during a twenty-four 
hour period uf submersion. Erperimental snail No. 1. Zero 
weight, 9.72 g. 

19.6% of the initial volume has been lost while at 
the end of 24 hr, a 28.3% reduction was observed. 

Volume reductions over five days of sub- 
mersion— Table 4 gives the results from ex- 
perimental snails which were maintained under 
experimental conditions for an additional four 
days. Figure 3 illustrates the results for one of 
these snails. The smooth weight increase (volume 
reduction) continues but at a reduced rate. The 
weight increase for the first day is equivalent to 
a gas volume reduction of 28.3% (Table 3) or 
29.5% (Table 4). The rate decreases to 4.0% of in- 
itial volume on the fifth day (equivalent to 0.17% 
of initial volume per hour). The total volume re- 
duction after five days is 46.2% of the initial 
volume. Although these snails were without food 
or access to air they appeared to be in good con- 
dition throughout the five day period. E^ch snail 
was active and tried to ventilate throughout the 


r. I 

Time (hours) 

FIG. 3. Underwater weight changes during a five day period 
of submersion. Experimental snail No. S. Zero weight. 9.72g. 

experiment by reaching upwards with its siphon. 
This behavior was characteristic of all experimen- 
tal snails. 

Buoyancy of smmls—\i has already been 
pointed out that these snails usually do not 
become buoyant under experimental conditions. 
The results of the one experiment in which the 
snail became buoyant is illustrated in Figure 4. 
The results presented for the snail of Figure 4 
are not given in either Tables 3 or 4. The snail of 
Figure 4 was neutrally buoyant after about 3 hr 
of submersion. At the end of nearly three days 
the snail was allowed to ventilate and it returned 
to its original buoyancy level. Following this ven- 
tilation, the weight increase with time was re- 
duced. This rate reduction may be a result of 
starvation, respiratory stress, and other undeter- 
mined experimental conditions. 

TABLE 3. Gas volume changes in the lung during a 2i hour pen 






(hs Volume 

at Start 


Vnderu>at€T Volume Reductxans on 

Successive Hoiin 






h' Hourv 




H Hours 





U Hours 




a Hours 




ilh ,5(/i 










0.96 0.74 













1.78 1.32 












0.80 0.69 












0.78 0.87 












2.50 1.98 












0.35 0.21 










Vol. 91 (3) 

July 1, 1977 


TABLE 4. Gas volume changes in the lung during a five day period of submersion. 

I'nderu'ater \ 

j/wmf Heductum 





Successive days 



Gas Vnlumr 






at Stan 

,5 Days 







5 Days 















































It should be pointed out that flotation is com- 
mon in these snails. On numerous occasions over 
50% of these snails have been observed to float in 
laboratory tanks. At other times all are sub- 
merged. In the field most of the snails collected 
are those which are floating. Collecting snails is 
easiest in the early morning because of the large 
numbers which are buoyant. By mid-day condi- 
tions have changed and floating snails may be 
difficult to find. 

Pomacea urceus is either buoyant or has a 
specific gravity of greater than one after each 
ventilation. Therefore these snails do not always 
return to the same specific gravity after each 
ventilation. However, one must ask if a level is 
maintained while floating or while submerged. 
Figure 5 gives the results of a snail (specific 
gravity greater than one) which was allowed to 
ventilate at will. This individual may return to 
the same weight level; it may go to a much lower 
specific gravity; or it may decrease the total gas 

volume during the process of ventilation. On two 
occasions this snail ventilated three successive 
times before a smooth weight increase was re- 
corded. This type of ventilating activity has been 
observed frequently in laboratory tanks. 

Siphonal ventilation in Pomacea urceics, P. 
falconensis, P. luteostoma, and Marisa cor- 
nuarietis.— During ventilation the tip of the 
siphon is brought into contact with the surface to 
form an air tube to the lung. The head of these 
ampullariids is then observed to contract in a 
pumping action. Adults of P. urceus are gigantic 
and are capable of extending their siphon by at 
least 1.5 times their shell length. A large snail of 
125 mm can easily extend its siphon about 200 
mm and makes little effort to reach the surface 
of shallow laboratory tanks. The juveniles of P. 
urceus and the adults of P. falconerms, P. 
luteostoma, and Marisa comuarietis all had max- 
imum shell dimensions of about 30 mm. 



2400 2400 

Tim* (hours) 

FIG. 4. Underwater weight changes of a snail which was 
buoyant after ventilation of its lung. Broken line indicates a 
decrease in weight when snail was allowed access to air after 
a period of nearly three days. 



/ / 





A / 




«. 15 











Zaro ■fllaril 


1200 laoo 

TImi (hours) 

FIG. 5. Undenrater weight changes after successive ventila- 
tions of the lung. Those weights marked by an X indicate the 
weight immediately after completion of a ventilation. Zero 
weight, 9.75 g. 


July 1. 1977 

Vol. 91 (3) 

Adults of P. urceus ventilate their lung every 
62 min with about 18 pumps per ventilation 
(Table 5). Juveniles of P. urceiw^ ventilate every 
20 min with about eight pumps per ventilation 
(Table 5). The difference between the adults and 
juveniles of P. urceus undoubtedly reflect size. 
The adults of P. falconemns and P. luteostoma 
were similar to juveniles of P. urceus in the in- 
terval between ventilations and in the pumps per 
ventilation (Table 5). In addition to the snails of 
Table 5, Marisa comuarietvi was also maintained 
in aquaria. All the ampuUariids regularly surface 
and actively ventilate their lung by extending 
and withdrawing their head-foot. They have all 
been ovserved to release from the bottom and 
float to the surface. They may also float for pro- 
longed periods as well as release gas at the sur- 
face and sink to the bottom. 


Unfortunately there are no published data on 
the underwater weights of ampullariids. There- 
fore many comparisons must be made with the 
extensive data of Henderson (1963) on freshwater 
pulmonate snails. 

This investigation has shown that Pomacea 
urceus regularly surfaces and ventilates its lung. 
This snail may become buoyant and float or 
maintain a specific gravity of greater than one. 
Ventilation normally occurs during the period of 

greatest weight change. This is also true of the 
pulmonates studied by Henderson (1963). For 
Henderson's pulmonates, the buoyancy level is 
apparently used as a very sensitive signal for sur- 
facing. This is not the case for P. urceus, which 
ventilates at various buoyancy levels (Fig. 5). En- 
vironmental oxygen tension is probably a more 
important signal for surfacing. McClary (1964) 
showed that the buoyancy in P. paludosa is 
reduced before surfacing, but believes that oxygen 
tension is probably the critical stimulus. Pomacea 
urce^ui maintains an overall specific gravity of 
greater than or less than one for periods of ac- 
tivity while continuously submerged or while 
floating. The apparent greater variability of sur- 
facing behavior in P. urceus may well be ac- 
counted for by the presence of a functional 
ctenidium. This provides an alternative: aquatic 
respiration with its gill or aerial respiration with 
its lung. Henderson (1963) points out that Lym- 
naea stagnalis and Planorbarius comev^ are very 
sensitive to disturbances and such will cause an 
increased amount of gas to be taken in at the 
surface. In P. urceus there is a sensitivity to 
vibration, movement near aquaria, and light 
changes. Such irritations may cause a snail to 
retract and remain inactive for long periods. 
However, there is no evidence that disturbances 
cause an increase in the amount of air taken in 
during ventilation. TTiis sensitivity increased as 

TABLE 5 Prpqiipnry and intensity of siphonal ventitation nf the Ivng in adultii nnd jiwenilfs o/ Pomacea urceus. and in P. 
falconensis and P. luteostoma. 




Pnmarea wrfpiw 

Pnmareft urcpus 

P falrnnrtuns 

P lutfoatfimo 

Number of .snails involved in observations 





Shell len^h (mm) 







about 90-125 











about 140-400 




Interval between ventilations (min.) 

Number of observations 















Standard Error 





Pumps per ventilation 

Number of observations 















Standard Error 





Vol. 91 (3) 

July 1, 1977 


the breeding season neared. During November 
when copulating pairs are common, experiments 
are impossible to perform. Therefore, these 
results are not representative of snails at all 
times. Further, P. urceits aestivates during the 
dry season and remains buried in the dry ground 
surface where aerial respiration is obligatory 
(Burky, Pacheco, and Pereyra, 1972; Burky, 1973, 

Over periods of 24 hours, Henderson (1963) 
reports that for L. stagnalis and P. comeus, 
56.7% and 52.2% of the gas bubble has been lost, 
respectively. For P. urceus, only 28.3% of the gas 
bubble has been lost for the same period. At the 
end of five days these pulmonates have lost 93.5% 
and 91.5% of the gas respectively, while P. urceus 
has only lost 46.2%. The lower percentages for P. 
urceiis probably represents a lower respiratory 
rate for this large snail. However, the ratio of gas 
volume to body tissue, as well as the presence of 
a gill are also involved. 

On occasion the interface of the gas at the 
pulmonary opening was observed. However, this 
opening is relatively small in the genus Pomacea 
(Andrews 1965b) and is probably not suitable as 
a diffusion interface. Further, there is no 
evidence that P. urceus uses the pulmonary gas 
as a physical gill. After ventilation some snails 
have been observed to retract and remain inac- 
tive on the bottom until just before the next ven- 
tilation. In these snails the pulmonary gas must 
be used as an oxygen store. 

It is known that the rate of aquatic respiration 
of snails decreases with oxygen tension (Berg and 
Ockelmann, 1959). Similarly it follows that the 
volume reductions for P. urcevs represent 
reduced rates of gas consumption with time. This 
has also been claimed for pulmonates by Hender- 
son (1963) who points out that the weight 
changes, although representative of volume reduc- 
tions, cannot be converted to oxygen consumption 
rates. There is a constant loss of nitrogen and 
other gases to the surrounding water. However, 
the rates reported by Henderson are of the same 
order as oxygen consumption rates reported by 
others for pulmonates. In P. urceus the weight 
changes can be assumed to be even less represen- 
tative of oxygen consumption rates since apart 
from cutaneous respiration there is a functional 

gill. Regardless, the initial hourly volume change 
for P. urceus is of the same order as the oxygen 
consumption rates of active adults (Burky, 
Pacheco, and Pereyra, 1972). 

It was observed that juveniles of P. urceus ven- 
tilate their lung more frequently than adults. 
This probably reflects a higher metabolic rate in 
the smaller snails. Significantly, these juveniles 
show ventilation frequencies which are similar to 
those for adults of other species with the same 
approximate size (P. falconensis and P. 
luteostoma, from Table 5; P. paludosa from Mc- 
Clary, 1964; Marisa comuMrietis from Demain, 
1965). The difference between juvenile and adult 
P. urceus may also reflect differences in the ra- 
tio of lung capacity to total tissue in relation to 
metabolic rate. 

It has been pointed out that more snails are 
observed to float during the morning in the field. 
Over vast areas of the savannah, greater than 
three meters of water may cover the savannah 
during the rainy season. Significantly the oxygen 
tension is lowest during the morning hours 
(Table 1). At times of high oxygen tension, in the 
aftemon and evening, there may be "less" de- 
pendency on aerial respiration. Andrews (1965b) 
points out that the ctenidium of ampullariids is 
relatively smaller that in other prosobranchs 
and that the genus Pomacea has a relatively 
large lung when compared to other ampullariids. 
The relative proportions of gill to lung support 
the field observations in relation to oxygen 
tensions and floating activity. 

Willmer (1934) studied the relation between 
the mode of respiration and the gas content of 
the water in a tropical fish, the yarrow. At low 
oxygen tension aerial respiration is used; at high 
oxygen tension and specific carbon dioxide ten- 
sions aquatic respiration is used; and at in- 
termediate gas concentrations both means of 
respiration are employed. It would be interesting 
to know the specific responses of Pomacea urceus 
to varying tensions of oxygen and carbon dioxide 
as well as the characteristics of its haemocyanin. 

Ampullariids possess a typical prosobranch 
ctenidium and it is unlikely that this could be of 
secondary origin (Andrews, 1965b). The develop- 
ment of the lung in ampullariids is unlike that of 


July 1, 1977 

Vol. 91 (3) 

pulmonates (Ranjah, 1942) and is a new secon- 
darily derived structure (Ranjah, 1942; Demain, 
1964 discussion and references therein). This sup- 
ports the primary ctenidial origin and the secon- 
dary pulmonary structure and physiological me- 
chanisms in ampullariids. As indicated in the in- 
troduction and above, more information on respi- 
ratory behavior and physiology will give a better 
basis to our concepts of the evolution of this pro- 
sobranch group and the structural-functional ba- 
sis for the colonization of amphibious-terrestrial 
habitats by these snails. 


We would like to thank Professor Jesus 
Pacheco for making facilities and equipment 
available; Eduardo Miranda and Oswaldo Tra- 
vieso for their assistance in collecting snails; Mr. 
T. Pain for the identification of the snails and 
Dr. W. D. Russell -Hunter for his continuing in- 
terest and constructive criticism of the manu- 
script. Voucher specimens are on deposit for 
future reference at the Delaware Museum of 
Natural History, no. 102235. 


Andrews, E. B. 1965a. The functional anatomy of the gut of 
the prosobranch gastropod Pomacea canaliculata and of 
some other pilids. Proc. Zool. Soc. Land. 145: 19-36. 

Andrews. E. B. 1965b. The functional anatomy of the mantle 
cavity, kidney and blood system of some pilid gastropods 
(Prosobranchia). J. Z<ioL 146: 70-94. 

Berg, K., and K. W. Ockelmann. 1959. The respiration of 
freshwater snails. J. Exp. Biol. 36: 690-708. 

Burky, A. J. 1973. Organic content of eggs and juveniles of an 
amphibious snail, Pomacea urceus (Muller), from the 
Venezuelan savannah and their ecological significance. 
Malac. Rev. 6: 59. 

Burky, A. J. 1974. Growth and biomass production of an am- 
phibious snail, Pomacea urceus (Muller), from the 
Venezuelan savannah. Proc. Malac. Soc. bond. 41: 127-143. 

Burky, A. J., J. Pacheco, and E. Pereyra. 1972. Temperature, 
water, and respiratory regimes of an amphibious snail, 
Pomacea urceus (Muller), from the Venezuelan savannah. 
Biol. BuU. 143: 304-316. 

Demian, E. S. 1965. The respiratory system and the 

mechanisn of respiration in Marisa comuarietis (L). Ark. 

Zool 17: 539-558. 
Fretter, V., and A. Graham. 1962. British Prosobranch 

Molhiscs. London: Ray Society. 
Henderson, A. E. 1963. On the underwater weights of 

freshwater snails. Z Vergl. Physiol. 46: 467-490. 
Jacobs. W. 1941. Die hydrostatische Bedeutung der At- 

mungsorgane von Wassertieren. S.B. Ges. Morph. Physiol 

Munch. 50: 45-52 (Citation from Henderson 1963) 
Lufty, R. G., and E. S. Demian. 1965. The histology of the 

respiratory organs of Marisa comuarietis (L.). Ark. Zool 

18: 51-71. 
Meenakshi, V. R. 1956. Physiology of hibernation of the 

apple-snail Pila virens (Lamarck). Curr. Sci. 25: 321-322. 
Meenakshi, V. R. 1957. Anaerobiosis in the south Indian 

apple-snail Pila iHrens (Lamarck) during aestivation. J. 

Z(x>l Soc India 9: 62-71. 
Meenakshi, V. R. 1964. Aestivation in the Indian apple-snail 

Pila-l. Adaptations in natural and experimental conditions. 

Camp. Biochem. Physiol 11: 379-386. 
McQary, A. 1964. Surface inspiration and ciliary feeding in 

Pomacea paludosa (Prosobranchia: Mesogastropoda: Am- 

pullariidae). Ma/<Kofo9ia 2: 87-104. 
Pelseneer, P. 1895. Prosobranches aeriens et Pulmones bran- 
ch i feres. A fr/i. Biol. Paris 14: 351-393. 
Robson. G. C. 1922. Notes on the respiratory mechanism of the 

Ampullariidae. Proc. Zool Soc. bond for 1922, 341-346. 
Prashad, b. 1925. Anatomy of the common Indian apple-snail 

Pilaglobosa. Mem. Ind. Mus. 8: 91-154. 
Prashad, B. 1932. Pila (the apple-snail). Indian Zool Mem. 4: 

Ranjah, A. R. 1942. TTie embryology of the Indian apple-snail, 

Pila globosa (Swainson) (Mollusca, Gastropoda). Rec Indian 

Mus. 44: 217-322. 
Russell -Hunter, W. 19.53a. On migrations of Lymnaea peregra 

(MQller) on the shores of Loch Lomond. Proc. Roy. Soc. 

Edinburgh. B65: 84-105. 
Russell-Hunter, W. 1953b. The condition of the mantle cavity 

in two pulmonate snails living in Loch Lomond. Proc. Roy. 

Soc Edinburgh. B65: 143-165. 
Russell-Hunter. W. 19.55. Endemicism in the snails of Ja- 
maica. QasgowNat. 17: 173-183. 
Russell-Hunter, W. 1964. Physiological aspects of ecology in 

nonmarine molluscs, p. 83-126. In Wilbur, K. M. and C. M. 

Yonge, eds. Physiology of Mollusca, Vol. I. Academic Press, 

Inc., New York. 
Troschel, F. H. 1845. Anatomie von Ampidiaria urceus und 

uber die Gattung Lam.'^tes Montf Arch. \aturgei<ch. 11: 

Visser, S. A. 1965. A study of the metabolism during aestiva- 
tion of the amphibious snail Pila oi-aia. West African J. 

Willmer. E. N. 1934. Some observations on the respiration of 

certain tropical fresh-water fishes. J. Exp. Biol 11: 283-306. 

Vol. 91 (3) 

July 1, 1977 



Clement L. Counts, III, John M. Dingess, and James E. Joy 

Department of Biological Sciences, Marshall University 
Huntington, West Virginia 25701 


The electrocardiographic configuration of the fi-eshwater mussel Lampsilis 
radiata ivas investigated and described using three standard leads, three 
augmented leads, and one unipolar lead. Electrocardiograms demonstrated 
depolarization complexes for both the atria and the ventricle. Longitudinal mean 
electric axis of the ventricle revealed anterior-to-posterior depolarization and 
repolarization from posterior-to-anterior. Heart rates were irregular and bradycar- 
dic due to the electrocardiographic measurement while the valves of the mussels 
were closed. 

Electrocardiographic studies in Bivalvia have 
been employed mainly as a measure of the ani- 
mals response to various environmental stimuli 
(Crozier and Stier, 1924; Pickens, 1965; Helm and 
Trueman, 1967; Trueman, 1967; Coleman and 
Trueman. 1972; Trueman, et al, 1973). The ma- 
jority of these studies used marine bivalves, 
freshwater species being almost completely ig- 
nored. Further, most moUuscan electrocardio- 
graphic studies have only one lead which results 
in presentation of "rhythm strips" which provide 
information only on heart rates and their regu- 
larity. The present paper describes the electrocar- 
diographic configuration of the North American 
freshwater mussel, Lampsilis radiata (Lamarck, 
1819), as revealed by a seven lead system. 


Electrocardiograms (ECGs) were made for 10 
specimens (6 males and 4 females) of L. radiata 
taken from Beech Fork of Twelve Pole Creek, 
Wayne County, West Virginia. The mussels were 
maintained in an aquarium for two weeks prior 
to recording the ECGs. Weight, water displace- 
ment, and shell dimensions were measured before 
each ECG was made. 

Two 25 gauge hypodermic needles were placed 
such that one needle entered between the mar- 
gins of the valves 2 cm from the anterior and the 
other 2 cm from the posterior margins of the um- 
bonal ligament. In this manner, electrodes were 

thus located at the anterior and posterior mar- 
gins of the pericardium. A third 25 gauge needle 
was placed in the foot, directly beneath the umbo 
(Fig. 1). All recording equipment was manufac- 
tured by Harvard Apparatus. The needles were 
connected to a model 369 EKG lead selector with 
a model 354 bioamplifier input module such that 
the anterior needle was connected to the left arm 
input, the posterior needle was connected to the 
right arm input, and the foot needle was con- 
nected to the left leg input. ECGs were preamp- 
lified with a model 371A preamplifier with a 
gain control variable to over 100 and a band- 
width of 0.2 Hz to 12.0 kHz at a gain of 100 and a 
bandwidth of 0.2 Hz to 4.5 kHz at a gain of 1000. 
A 10-speed chart mover (0.005 cm/sec to 5 cm/ 
sec) equipped with a model 283 event/time mark- 
er module (1 min/ 10 sec/ 1 sec intervals) and a 
model 350 recorder were used. 

Leads measured were I, II, III, aVR, aVL, aVF, 
and a single unipolar lead recorded by connecting 
the foot electrode to the chest input jack. ECGs 
were measured at a variable speed and amplica- 
tion. Once amplitude was established for a mus- 
sel, the entire ECG was run at that amplitude. 
ECGs were run continuously, using lead II, for 
one hour intervals to determine rhythmicity. All 
E£Gs were obtained while the mussels were lying 
on their left valve in a wooden pan of water at 


July 1, 1977 

Vol. 91 (3) 

FIG. 1. Placement of the needle electrodes in L. radiata. The 
left arm electrode (LA) was placed in the anterior end of the 
mitssel and the right arm electrode (RA) was placed in the 
posterior end. The left leg electrode (LLj was placed in the 
foot and was used to record the single unipolar lead (VJ. Elec- 
trodes were connected to appropriate input jacks an an EKG 
lead selector. 

Electrocardiographic intervals analyzed were 
the QRS complex (which measures the time 
elapsed during contraction (depolarization), and 
the strength on contraction), the T wave (which 
measures the elapsed time during which the 
heart prepares for the next contraction (re- 
polarization)), and the QT interval which meas- 
ures the total elapsed time between depolariza- 
tion and repolarization. The mean electrical axis, 
which is a measure of the general direction of 
depolarization and repolarization, was deter- 
mined by taking the algebraic sum of R waves 
( + ) and S waves (-) of leads I and III and plot- 
ting the result on a triaxial reference system. The 
axis was measured in the longitudinal plane due 
to the placement of the needle electrodes and was 
measured for both depolarization and repolariza- 
tion of the ventricle. 

The bivalves were identified by Dr. David H. 
Stansbery of the Ohio State University Museum 
of Zoology, The Ohio State University, Columbus, 
Ohio, where voucher specimens were placed in 
the collections. Other voucher specimens are in 
the Marshall University Malacological Collection 
(MUMC 17), Marshall University, Huntington, 
West Virginia, and the Delaware Museum of 
Natural History, Greenville, Delaware (DNMH 


Interpretation of the ECG wave components of 
L. radiata was complicated by the presence of 

two distinct QRS complex forms (Fig. 2). TTiese 
complexes could not be related to each other in 
terms of duration or sequence timing. As the 
heart of L. radiata is composed of a single ven- 
tricle and two smaller atria, connected to the 
ventricle by small vessels, and the ventricle is the 
largest chamber of the heart, the strongest QRS 
deflections were interpreted as being ventricular 
in origin and the smaller complexes as origi- 
nating from the atria. Tliis phenomenon was best 
seen in leads I, aVL, and the unipolar foot, or V 
lead, in the majority of tracings. The QRS of the 
ventricle (QRS,) had a mean duration of 1.4 sec 
(range 0.8-2.0 sec) and the mean duration of the 
atrial QRS complex (QRS.) was 0.6 sec (range 
0.6-0.8 sec). The smaller size of the QRS. is to be 
expected as the atria are smaller and the amount 
of work necessary to pump blood to the ventricle 
is less than that required to pump blood to the 
entire body. The shorter duration of contraction 
periods of the atria support this supposition. 
Also, the longer contraction periods of the ven- 
tricle may be necessary to pump the molluscan 

FIG. 2. Representative electrocardiogram of L. radiata 
demonstrating the independently occurring ventricular (QRS.) 
and atrial (QRS.) depolarization complexes. 

Vol. 91 (;?) 

July 1, 1977 


blood by a "milking" action of the ventricle. Ven- 
tricular QRS complexes were seen to be positive 
deflections only in a Vr and were negative in all 
other leads. 

No T waves could be demonstrated for the 
QRS„ as they occurred during the repolarization of 
the ventricle. This is explained by the fact that 
the repolarization signal of the ventricle, being 
stronger than the repolarization wave of the 
atria, wall take precedence over weaker signals. 
Thus, the repolarization of signal of the atria was 
buried in the T wave of the ventricle. Ventricular 
T waves had a mean duration of 2.2 sec (range 
1.3-4.6 sec). T waves were negative only in aVr 
and were positive in all other leads. 

The placement of the electrodes (Fig. 1) 
allowed measurement of the mean electrical axis 
in the longitudinal plane which was desirable, as 
the heart of L. radiata lies in this plane. The 
mean electrical axis of ventricular depolarization 
(Fig. 3) was -165° (range -111' - +54°) while 
the mean axis of ventricular repolarization was 
-21° (range ±0° -60°). Thus the ventricle of L. 
radiata depolarizes, or contracts, in an anterior 
to posterior direction and repolarizes posterior to 
anterior. This may be visualized by superimpos- 
ing Figure 1 over Figure 3. 

The heart rate of L. radiata had a mean of 9.5 
beats/minute (range 3-18). Rates were irrregular- 
ly irregular and long periods of asystole were 
noted in some ECGs. Ventricular QT intervals 

FIG. 3. Mean electrical axis and distribution for ventricular 
depolarization (QRS) and repolarization (T) in L. radiata. 
Arrows indicate the arithmetic mean of these axes. 

had a mean duration of 3.5 sec (range 1.6-60 sec). 
Other studies (Coleman and Trueman, 1971; 
Trueman and Lowe, 1971) demonstrated brady- 
cardia in the ECGs of marine Bivalvia recorded 
while the valves were closed. All of the ECGs of 
L. radiata were recorded under these conditions. 
The low heart rates may be due to reduced 
metabolic requirements when the valves are 
closed (Hill and Welsh, 1966; Coleman and 
Trueman, 1971), and our data suggests the same 
mechanism may be present in freshwater mus- 
sels. However, further studies are necessary to 
determine if the position in which the ECGs were 
recorded, which was different from the position 
normally assumed by the mussels in their natu- 
ral habitat, plays a significant role in heart rate. 
Another aspect of interpretation of ECGs from 
mussels by the technique used in this study is the 
degree of change in "normal" ECG findings 
caused by the invasive method of electrode place- 
ment. No correlation between weight, size, or sex 
could be found for the electrocardiographic inter- 
vals measured. 


Coleman, N., and E. R. Trueman. 1971. The effect of aerial ex- 
posure on the activity of the mussels Mytilus edtdis L. and 
Modiolus modiolus (L.). Jour. Exp. Mar. Biol. Ecol. 7: 

Crozier. W. J., and T. B. Stier. 1924. Temperature 
characteristics for heart beat frequency in Umax. Jour. 

Helm. M. M.. and E. R. Trueman. 1967. The effect of exposure 
on the heart rate of the mussel Mijtilns edulis L. Comp. 
Biochem. Physiol. 21: 171-177. 

Hill. R. B., and J. H. Welsh. 1966. Heart, circulation, and 
blood cells. In, Physiology of Mollusca. Vol. 2, K. M. Wilbur 
and C. M. Yonge, Eds. Academic Press, New York. pp. 

Lowe, G. A., and E. R. Trueman. 1972. The heart and water 
flow rates of Mi/a arenaria (Bivalvia: Mollusca) at different 
metabolic levels. Comp. Biochem. Physiol. 41 A: 487-494. 

Pickens, P. E. 1965. Heart rates of mussels as a function of 
latitude, intertidal height, and acclimation temperature. 
P/!!/s!:o;. Zoo/, 38:390-405. 

Trueman. E. R. 1967. Activity and heart rate of bivalve 
molluscs in their natural habitat. Nature 214: 832-833. 

Trueman. E. R... and G. A. Lowe. 1971. The effect of 
temperature and littoral exposure on the heart rate of a 
bivalve mollusc, Isognomon alatus. in tropical conditions. 
Comp. Biochem. Physiol. 38 A: 555-.564. 

Trueman. E. R.. J. G. Blatchford, H. D. .Jones, and G. A. Lowe. 
1973. Recordings of the heart rate and activity of molluscs 
in their natural habitat. Malacologia 14: 377-383. 


July 1, 1977 

Vol. 91 (3) 


Dee S. Dundee 

Department of Biological Sciences 

University of New Orleans 

New Orleans, Louisiana 70122 


During the past decade veronicellid slugs have entered the United States. Some 
of them have become established and are spreading. These slugs are associated 
with the movement of plant materiah and are affected by insecticides used on 
plants. Environmental factors which influence them are temperature, wind, light, 
pH and relative humidity. Tiro reproductive periods per year occur, with each slug 
depositing several (1-5) egg masses containing up to 15 ova per mass. A pathogenic 
dviease, which might serve as a biological control, occurs when the individuals are 
crowded. The significance of these introductions cannot be underestimated in view 
of the problems encountered in past biological introductions in various parts of the 

In 1960 a veronicellid slug was first found in 
the Gulf Coast area in Mobile, Alabama, and 
New Orleans, Louisiana. It had not been taken 
prior to that time in any of the extensive collec- 
tions which had been made in connection with a 
molluscan survey (Dundee, 1970; Dundee, et al., 
1965), nor had it been reported in the literature. 

Here, then, was a perfect opportunity to work 
with an introduced species from the probable 
time of its introduction. Since then, its ever- 
widening distribution has been documented, its 
life cycle studied, its anatomy has been charted 
(Petrellis and Dundee, 1969), and study of its 
ecological requirements has begun. 

This slug is Veronicella ameghini Gambetta. 
This identification is based upon comparisons of 
these slugs with types residing in European mu- 
seums. For this I thank Dr. Jose Thome of Port 
Alegre, Brasil, who is currently working on the 
nomenclature of the Veronicellidae. V. ameghini 
is endemic to Rio Grande do Sul, Brasil. 

During the spring of 1970 another veronicellid, 
Veronicella floridana (Leidy) was reported in 
New Orleans and since then several other local- 
ities for it have been discovered in the city. 

The United States Department of Agriculture 
has reported Veronicella moreleti (Crosse and 
Fischer) from Brownsville, Texas, and Vaginulus 

occidentalis (Guilding) from McAllen, Texas, and 
state that a third unidentified species was taken 
from Raymondville, McAllen, Edinburg and San 

Thus, it is obvious that veronicellids are mov- 
ing into the south with rapidity, making it im- 
perative that we have information on them. 


Veronicella floridana can be considered native 
in the south Florida area. Only recently has it 
begun to spread into other Gulf Coast areas 
(Figure 1). 

Veronicella ameghini was first discovered in 
New Orleans and Mobile in 1960. Our last survey 
of the area (summer 1970) revealed its present 
distribution as shown in Figure 1. 

The other records are those of slugs found in 
nurseries and/or greenhouses. Thus far they have 
not, to our knowledge, become established else- 
where, but it is probably only a matter of time 
until they do. The means of distribution is 
through the moving of plants by man. Most likely 
the egg masses deposited in the soil around the 
plants are the stage transported since nursery 
operators generally pick off and kill any visible 

Vol. 91 (3) 

July 1, 1977 







9 50 i()o zoo 390 

FIG. 1. Distribution of veronkellids in the United States. 

adults or young. It is obvious that the Gulf Coast 
provides suitable habitats for these animals and 
we can expect to see more of them colonize the 
area as time goes by. 



Population densities: Dundee, Stutts, Hermann 
(1965) provide an adequate description of a ty- 
pical habitat. Population densities in these ha- 
bitats fluctuate greatly. In the New Orleans area 
both slug populations, which are usually associ- 
ated with the grass, Stenotaphrum secundatum, 
fluctuate tremendously. In peak seasons such as 
1965, populations were very large; in one 375 sq. 
m. area we were able to collect the following num- 
ber of slugs in a half hour period: July 13 (584), 
August 10 (454), September 15 (254). All slugs 
were returned to the habitat after collection. 

During the next eight years the populations 
fluctuated considerably (Figure 2). By 1973, they 
were at the lowest ebb since introduction. In fact, 
they were so scarce that the author wondered if 
they were dying out in the area. Note that, while 
measurements of the population were made in 

the one area routinely, casual observations were 
made in numerous areas since the author had 
some concern about the effects on the population 
of using the same area regularly. Those substan- 
tiated the measured results. As any collector well 
knows, one is well aware of relative population 
densities over a period of time, if one is collect- 
ing or observing in an area regularly. 

Stenotaphrum secundatum (St. Augustine 
grass) used widely as a lawn grass, is subject to 
damage by chinch bugs, Blissus leucopterus. As a 
result, lawns throughout the south are routinely 
treated with various products: Ortho Malathion 
50, Cygon, Ortho Dieldrin, and others. These di- 
rectly affect the slugs living in the grass. During 
the summer of 1970, for example, in the New Or- 
leans area the bug problem was severe and much 
spraying was done. 

A simple experiment (Table 1) involving 
various easily obtainable insecticides and 
molluscicides was run to determine the effects of 
these on the slugs. Slugs were placed in a con- 
tainer identical to their usual laboratory hous- 
ing: lightly moist sand on the bottom with part 
of it covered by a piece of paper toweling. The 


July 1, 1977 

Vol. 91 (3) 

TABLE 1. Results of lab tests with molluscicides and insecticides (10 slugs of each species were used in each trial/ 



Hou- Applied 

Amimnt of Kill 



Set in container 

all dead in 24hrs. 



Set in container 

all dead in 24 hrs. 

Green Lite 

Crushed form 

Sprinkled in container 

all dead in 24 hrs. 



Dog biscuit saturated and 
placed in container 

all dead in 24 hrs. 

1 mi in 800ml water sprayed 

no deaths after 72 hrs. 

2 ml in 800 ml water sprayed 

4 dead in 24 hrs. 

2.5 ml in 800 ml water sprayed 

9 dead in 24 hrs. 

5.0 ml in 800 ml water sprayed 

all dead in 24 hrs. 

Malathion 5() 


Dog biscuit saturated and 
placed in container 

all dead in 24 hrs. 

1 ml in 800ml water 


no deaths after 72 hrs. 


no deaths after 72 h rs. 

3 ml 

no deaths after 72 hrs. 


much wTithingbut 
alive after 72 hrs. 

Cygon -2E 


Dog biscuit saturated and 
placed in container 

all dead in 24 hrs. 

1 ml in 800 ml water sprayed 

no deaths after72hrs. 

5 ml in 800 ml water sprayed 

no deaths after 72 hrs. 

6.7,8 ml in 800 ml water sprayed 

no deaths after 72hrs. 

9 ml in 800 ml water sprayed 

all dead in 24 hrs. 

application of the chemicals was as shown in 
Table 1. 

Three of these chemicals, Snarol, Bug-Geta, and 
Green Lite, are specific for snails and slugs. 
Snarol's active ingredients are tricalcium 
arsenate and metaldehyde. Green Lite has hex- 
achlor - epoxy - octahydrodimethanonaphthalene 
(0.5% Dieldrin) and metaldehyde. Bug-Geta con- 
tains calcium arsenate and metaldehyde as active 





i 300- 

The others are insecticides. Dieldrin, designed to 
kill beetles, ants, grasshoppers, box elder bugs as 
well as "many other lawn and ornamental soil in- 
sects", is composed of dieldrin (see above) and an 
aromatic petroleum derivative solvent. Malathion 
50 is designed "for use on evergreens, roses, or- 
namentals, shrubs, trees" and is meant to control 
red spiders, aphids, flies, mealybugs, scale insects 
as well as various other household pests. It is a 
choline esterase inhibitor. Active ingredients are 










FIG. 2. Population densities of V. ameghini in one 375 sq. meter area. Left column of each year represents a mid-July collec- 
tion, middle is mid-August, and right is mid-September. 

Vol. 91 (;3) 

July 1, H»77 








5 3 



3 3 



1 i ^ \ 



2 1 

5 1 


4 2 


1 3 2,1 





' "1, 





3 3 








S 1 



1 1 

2 1' 

4 2| 






5 l| 


3 2 1 


r 2 

2 1 


1 4 1 






3 3 


2 112 1 

1 1 1 1 1 

1 1 

1 1 1 1 1 1 

1 1 1 1 



1 1 1 


1 1 

I I I I I I I I I I I I I I I I I I I I I I I I I I I 

24 26 28 30 31 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 


54*- 82' TOLERANCE 

FIG. .3. Temperature tulerance in Veronicella ameghini. Bars indkate the temperature range tu which the slugs were exposed 
in each experiment. 

malathion (0, 0-dimethyl dithiophosphate of di- 
ethyl mercaptx)succinate) and an aromatic petro- 
leum derivative solvent. Cygon 2-E has as an ac- 
tive ingredient dimethoate (0, 0-dimethyl S-(N- 

Although a much broader experiment with 
more variables such as size of area, moisture con- 
trol, would, of course, be more desirable, it is ap- 
parent from Table 1 that, even with these simple 
tests, these insecticides used for lawns (as well as 
the molluscicides which are for sale) are very 
quickly detrimental to the slugs. This could be a 
significant factor in population fluctuations. 

Temperature. Experiments patterned after 
Dainton(1954) were run numerous times to deter- 
mine temperature tolerance. The temperature 
measured was that of the air immediately above 
the substrate upon which the slugs were resting. 
In each trial, except one, 6 slugs were used. No 
difference in species behavior was found. Repeat- 
edly the results were shown in Figure 2 wherein 
the range of tolerance falls between 12 and 28°C 
(54-82°F) with the preference seeming to be 
20-24T (68-75°F). When the temperatures fall 

below 12°C (34°F) inactivity prevails whereas if 
it rises beyond 28T (82°F) and remains even 
for a short period of time, death ensues. In 
relating these data to the situation in nature, one 
must remember that the soil temperature in the 
micro-habitat is modified by other factors not in- 
volved here: shade, wind, humidity. For example, 
we have collected active slugs when the air 
temperature was 10°C, but simultaneously the 
relative humidity was 92% and the slug substrate 
was approximately 23°C due to a warm water 
sewer close by (see section on relative 

Light. In another series of experiments involv- 
ing a combination of temperature and light 
several factors were discovered. When air 
temperatures have been higher than 3rC (88°F) 
and begin decreasing, the slugs begin activity 
whereas when temperatures have been lower 
than 25°C (77°F) and are increasing, activity 
does not begin to occur until 25°C is reached 
even though this is above the preferred range 
(20-24°C) as demonstrated in the substrate 
studies. Since these temperatures approximate 


Julv 1, 1977 

Vol. 91 (3) 

the summer season daily temperature range 
(21-30T) here, this leads us to superimpose 
light as a factor directing slug behavior. We 
discovered that slugs (in our experimental 
chamber) moving towards a cooler area, will, if a 
light (anywhere from 44 to 260 foot candles) is 
directed at their anterior ends, go in the reverse 
direction even if the temperature is intolerably 
high there. Several such experiments lead us to 
believe that temperature controls time of activity 
but that light determines the area of activity. All 
of these factors together could account for noc- 
turnal activity which is seen normally. But, the 
further problem of desiccation must also be con- 

Wi-nd. A series of experiments to test for ef- 
fects of wind upon the slugs was done. Superim- 
posed upon these experiments were additional 
conditions of heat, light and temperature. 

The method of procedure was as follows: a 
clear, plastic box 25 cm wide X 17.5 cm high X 
15 cm deep, with moist paper toweling on its 
floor and sides, was used as the light chamber. A 
similar box with all sides painted black served as 
the dark chamber. A partial barrier (15 cm high 
X 5.5 cm wide) was taped upright in the right 
front side of each box. The box was turned so 
that the top faced frontwards to the path of the 
air from a small electric fan. Screen covered the 
top (front) of each box. Twenty slugs (the ex- 
periments involved each species) were placed in 
each chamber approximately 2.5 cm abeam of the 
plastic wind barrier. Exposure time was planned 
to be fifteen minutes per experiment; however, 
under certain conditions the animals were dying 
sooner so that results were obtained more quickly. 

The animals were observed and responses 
recorded. A control set was maintained in a 
similar box for each experiment but without the 
variables (wind, hot, cold)— simply at room condi- 
tions. No behavior similar to that observed in the 
experiments was seen. Terminology used was as 

barrier area: that portion of the box behind the 
plastic barrier (the area sheltered from the 

exposed area: the rest of the box 

aggregation: animals close together so as to form 

a group; characterized by a mound-like ap- 
pearance and complete or near complete 
absence of motion 

random orientation: any motor activity not 
specifically directed towards the barrier area; 
includes extension -retraction of tentacles, mo- 
tion of anterior body and/or actual movement 
into the barrier area 

sheltered activity: activity occurring after the 
animal had reached the barrier area but which 
was not directed towards the outside of that 

temperature: room temperature was 22°C 
(72°F). Heat was introduced into the boxes by 
placing a hot-plate directly in front of the fan. 
Temperatures as high as 33°C (92°F) could be 
attained by this method: however, tem- 
peratures between 23 and 29°C (74-84°F) 
were used since it was determined that the 
animals would not survive above 28°C (84°F); 
again this verified previous experiments. 
A summary of results follows: 

Experiment 1 (repeated ten times with each 
species): light box— room temperature— wind 

1. Animals initially stationary; no motion for 
first five minutes. 

2. Random orientation on the part of three 
animals; others motionless or with only 
slight movement. Lasted 6-15 minutes. 

3. By the end of twenty minutes, most animals 
had migrated to the barrier area. 

4. Remaining animals aggregated. 

Note: Attainment of barrier area did not 
necessarily indicate cessation of movement. On 
a number of occasions sheltered activity con- 
tinued. In some cases, animals having attained 
the barrier area early would return to the ex- 
posed area to any clustered group. One time 
when a single slug attained the barrier area 
and the others clustered in the exposed area, 
that individual returned to the cluster. Under 
conditions of exposure all animals secreted 
mucus heavily unless clustered. This occurred 
in both the light and the dark. 

Experiment 2 (repeated ten times with each 
species): Dark box— room temperature— wind 

Vol. 91 (3) 

July 1, 1977 


1. The same absence of activity for the first 
five minutes. 

2. Much less activity for the first ten minutes 
than in the light. 

3. Some random orientation leading to 
clustering by most; in some of the ex- 
periments several slugs had, by the end of 
fifteen minutes, attained the barrier area 
and ceased activity. 

Note: There was much less activity in the dark 
than in the light when wind was applied. 

Experiment 3 (repeated ten times with each 
species); Light box— heat— wind (fan) 

1. Motion often leading to aggregation in first 
five minutes. 

2. Random orientation leading to signs of 
shriveling accompanied by increase in ac- 
tivity for next ten minutes. Those reaching 
the barrier area often returned to the ex- 
posed area. Appearance of general discom- 
fort; the higher the temperature, the 
greater the appearance of discomfort (in 
combination with wind) 

Experiment 4 (repeated ten times with each 
species); Darkbox— heat -wind (fan) 
1. Aggregation was the response within the 
first five minutes with no other behavior oc- 
Experiment 5 (repeated ten times with each 
species); Light box— cold (whole experiment 
placed in 3T (;38°F)-wind (fan) 

1. Immediate shriveling. 

2. Moved into an aggregate within two 
minutes; appear "pinched"; very heavy 
mucus secretion. 

Experiment 6 (repeated ten times with each 
species); Dark Box— cold— wind (fan) 
1. Aggregation close to point of release 
followed by inactivity; same appearance 
and mucus as in light-cold. 

Several interesting results were obtained from 
these experiments. First, it is obvious that 
veronicellids have a negative response to wind 
and either seek shelter or aggregate in the 
presence of it. The temperature of the wand seems 
to be of no more importance than temperature 
alone (based upon a comparison of these ex- 
periments with the previously-discussed tem- 

perature experiments). The reason for less activi- 
ty in the dark than in the light is as yet unex- 
plained; it is the reverse of the situation without 

pH: the range in soil pH in areas where slugs 
are common is 7.2-7.8. 


There are two periods of egg deposition by 
Veronicella ameghini in the Gulf Coast area. One 
is from March through June and another from 
September through mid-November. The same tim- 
ing prevailed in the laboratory despite different 
experimental conditions. 

E^s are normally deposited in a shallow con- 
cavity which the slug makes in the soil. This 
usually occurs under leaf litter where a higher 
moisture level is likely to be maintained. The egg 
mass is coiled and the eggs are attached together 
by a gelatinous, fecal-containing strand. The slug 
deposits the strands while it is curled in the form 
of a circle. The curve of the body apparently 
helps form the coil-shaped egg mass. A single slug 
may deposit from one to five masses during each 
breeding season. Five to fifteen eggs are laid in 
this manner and the period of deposition is 
known to be at least five hours. Each egg is oval, 
6 mm in length 3 mm wide, gelatinous without a 
hard cover. Once deposited, the eggs are not 
covered over with soil but are merely left to 

Hatching occurs in approximately 20-28 days 
depending on the temperature. The average in- 
cubation period in the laboratory with a room 
temjjerature averaging 24°C was 21.4 days. The 
late spring masses hatch sooner than those laid 
in early spring, probably due to a higher 
temperature; likewise, the later fall eggs require 
a longer period to hatch. 

Length of newly hatched slugs is about 3-4 
mm. It is impossible to accurately measure living 
slugs; therefore, weighing was employed. Average 
weight of a newly hatched slug .016 g. 

Grovrth rate in the laboratory is slow. Here 
they were maintained at room temperature (ap- 
proximately 24°C or 76°F with air condition- 
ing) and fed lettuce. The average rate was 0.28 g 
in six months. The average weight of hundreds of 


.Julv 1. 1977 

Vol. ;»1 (3) 

slugs collected at random throughout the year 
was 0.523 g. It is suspected that the average 
growth rate in laboratory is well under that in 
the field. 

The largest adult captured weighed 2.94 g. If 
the alx)ve-mentioned growth rate does occur in 
nature the calculated age would be approximate- 
ly five years for this individual. Longevity is 
more likely around two years as it is with many 
other land molluscs. Laboratory maintenance is 
difficult for periods longer than six months. One 
has a constant die-off as time goes by. The prob- 
lem is one which is being investigated in more 
detail— namely, that of a blistering phenomenon 
wherein the slugs become pitted, form blisters 
and gradually become weak and die. It is thought 
that the disease is caused by either a yeast or a 
bacterium (DeGravelle, 1971). 


Repeated checks in nature and in greenhouses of 
our local colonies of Veronicella ameghini and 
Veronicella floridana reveal no significant 
damage from them to native vegetation, crops, or 
property. The latest finding of veronicellids in 
southern Texas is new enough that no informa- 
tion is available on their activities. USDA does 

rep(jrt that damage has been done to greenhouse 
plants by these slugs. The author has received a 
picture of damage done to bananas in Honduras 
by V(ujmuhis olivaceous (courtesy of Div. of Trop. 
Res., Dept. Entomology, La Lima, Honduras). It 
shows holes and browm spots where the slugs 
have rasped the banana "peel", thus making the 
banana unmarketable. 

With more introductions being reported recent- 
ly, it is well that we stay alert and be prepared 
with knowledge in case of any major problems 
such as have been associated with introductions 
of Achatinafidica, the giant African snail (Mead, 


Dainton. B. H. 1954. The activity of slugs. ./ Erp. Biul. 31: 

DeGravelle. L. 1971. An investigation of a blistering condition 

in the slug. Vcrdiiici'lla amcyhDu. MS Thcsix: Louisiana 

State University in New Orleans. 
Dundee, D. S. 1970. Introduced Gulf Coast Molluscs. Tulane 

Studies inZool. andBot. 16(3): 101-115. 
Dundee. D. S., B. S. Stutts. and P. W. Hermann. 1965. 

Preliminary survey of a possible molluscan pest in the 

southern United States. Ecol 46(1&2): 192-193. 
Mead. A. R. The Giant African Snail: A pmhlem in economic 

nialiu-dliyi/. Univ. Chicago Press. 1961. 
Petrellis, L.. and D. S. Dundee, 1969. Veronicella ameghini 

(Gastropoda): Reproductive. Digestive and Nervous 

Systems. Trans. Amer. Micr Soc. 88(4): 547-558. 

V(.l. 91 (:?) 

July 1. 1977 



Ralph W. Taylor, Michael P. Sweeney, and Clement L. Counts, III 

Department of Biological Sciences 

Marshall University 
Huntington, West Virginia 25703 

Pseudoscorpions are noted for their phoretic 
associations with many living vertebrates and in- 
vertebrates (Muchmore, 1971). However, their 
associations with non-living animal remains for a 
survival advantage has not been documented. 
Specimens of Chthonitis tetrachelatus (Preyssler) 
and Apochthonius moestus (Banks) have been col- 
lected by us from the empty shells of the ter- 
restrial gastropods Diodopais alholahri.'^ (Say and 
Mesodon thyroidvs (Say) from Cabell, Kanawha, 
Putnam, and Wayne Counties, West Virginia. 
The empty shells were collected from mid- 
February to May, 1976, and the pseudoscorpions 
were collected in them up to April. 

The use of gastropod shells by arthropods is 
not an uncommon occurrence in the marine and 
littoral environment, as demonstrated by several 
species of hermit crab. Indeed, the use of ter- 

restrial gastropod shells by pseudoscorpions may 
have the same survival advantage in protecting 
the animal's soft parts during molting. However, 
this behavior may have other implications. The 
shells may offer protection from excessive cold, 
heat and desiccation. 

We would like to thank Drs. Sigurd Nelson, 
Jr., SUNY at Oswego, New York, William B. 
Muchmore, University of Rochester, and C. 
Clayton Hoff, University of New Mexico, for their 
advice and assistance. Voucher mollusk speci- 
mens are in the Marshall University Malaco- 
logical Collection and the Delaware Museum of 
Natural History. 


Muchmore. William B. 1971. Phoresy by North and Central 
American pseudoscorpions. Proc. Rochester Acad. Sci 12: 

Steven T. Malek 

826 Fern Street 
New Orleans, Louisiana 70118 

A comprehensive review of introduced mollusks 
in eastern North America (North of Mexico) was 
recently published by Dundee (1974). The tropical 
veronicellid slugs introduced in the above area 
received attention in the review. In the summer 
of 1975 I collected veronicellids in New Orleans, 
in the uptovm region of the city. These slugs fit the 
description of Veronicella nccidentalis (Guilding). 
This is a new record for this slug in Louisiana. 
About twenty slugs were found under logs, 
garbage cans and leaves, and on side-walks. 

Veronicella occidentalis was reported by 
Dundee (loc. cit.) to have been introduced into 
Oklahoma and Texas. The slug is believed to have 
originated in southern Mexico, northwestern 
South America and the Antilles. I have seen and 
examined specimens collected on the Caribbean 
Island of St. Lucia (E. A. Malek, 1976, in press), 
and the Louisiana material is quite identical to 
those from St. Lucia. These tropical slugs were 
probably introduced into the United States on 
several plants, judging from interceptions by the 


Julv 1, 1977 

V.)l. 91 (3) 

U. S. Department of Agriculture, at ports in 
Florida, Louisiana, New York and Texas. Among 
the plants are bromeliad, caladium, Dracaena sp.. 
Funis, orchid, palm, pineapple, and philodendron. 

Another veronicellid previously introduced in 
Louisiana, circa 1960, is Veronicella ameghini 
(Gambetta), and was reported upon by Dundee 
and Herman (1968). The latter slug occurs now in 
small numbers, that it is rarely encountered in 
New Orleans. It did, however, occur in large 
numbers in New Orleans in the early 1960's. 

I am grateful to Dr. Dee Dundee of the Univer- 
sity of New Orleans for having e.xamined the slugs 
which I collected in New Orleans, and having 
confirmed my identification. 


Dundee. D. S. 1974. Catalog of introduced molluscs of 
eastern North America (North of Mexico). Sterkiana No. 
55: 1-37 

Dundee. D. S. and Herman, P. W. 1968. New records for in- 
troduced molluscs. NautUus. 82: 43-45. 

Malek, E. A. 1976. Land and freshwater snails of St. Lucia, 
the West Indies. Tidane Studies ZooL Bot. (in press). 


Department of Invertebrate Zoology— Mollusca 

Several changes have occurred recently in the 
malacological staff of the Department of In- 
vetebrate Zoology, National Museum of Natural 
History, Smithsonian Institution, Washington, 
D.C. 20560 (formerly known as Division of Mol- 
lusks, U.S. National Museum). 

Dr. Arthur H. Clarke joined the staff in Janu- 
ary, 1977, as Associate Curator of freshwater and 
land mollusks in the position created by the 
retirement of Dr. J. P. E. Morrison (1975). Dr. 
Clarke formerly was curator of Molluscs and 
later Head, Invertebrate Zoology Division at the 
National Museum of Natural Sciences, National 
Museums of Canada, Ottawa. 

Dr. Richard S. (Joe) Houbrick became an Asso- 
ciate Curator in marine mollusks in March 1977, 
transferring from the Smithsonian Oceanographic 
Sorting Center (NMNH), where he supervised the 
benthic invertebrate sorting program. Dr. Hou- 
brick occupies the vacancy created by the retire- 
ment of Dr. Harald A. Rehder (1976). 

Dr. Rehder remaines in mollusks as Zoologist 
Emeritus, Department of Invertebrate Zoology. 

Dr. C. F. E. Roper and Dr. Joseph Rosewater 
continue to serve as Curators in cephalopods and 
marine mollusks, respectively. 

Each department of the National Museum of 
Natural History (Anthropology, Botany, Eii- 
tomology. Invertebrate Zoology, Mineralogy, 
Paleobiology and Vertebrate Zoology) is ad- 
ministered by a chairman. The Departmental 
chairmanship is a rotating position so that no in- 
dividual Curator need have his research program 
permanently curtailed. Curatorial staff are ad- 
ministratively responsible to the Department 
Chairman, as divisional Head Curators no longer 
exist. The subject areas within the Department of 
Invertebrate Zoology are Crustacea, Echinoderms, 
Lower Invertebrates, Mollusca, and Worms. Ad- 
ministrative requirements within a subject area 
are attended to by a Supervisor, a position 
rotated among the curatorial staff every year or 
two. Requests should be directed to the Super- 
visor or to a specific curator.— C. F. E. Roper. 

Vol. 91 (3) 

July 1, 1977 



Thompson, Fred G. 1977. The Hydrobiid Snail 
Genus Marstonia. Bull. Florida State Mus., 
Biol. Sci., vol. 21, no. 3, pp. 113-158. Eight 
species, of which five are new, are treated 
systematically. The genus, limited to Southeast 
and Central United States, is placed in the sub- 
family Nymphophilinae Taylor, 1966. $1.75, 
Florida State Nuseum, Gainesville, Fl. 32611. 

Thompson, Fred G. and Richard Franz. 1976. 
Some Urocoptid Land Snails from Hispaniola. 
Rev. Biol. Trop., vol. 21, no. 1, pp. 7-33, 9 figs. 
Allocoptis ne6rms,new genus and species, and 
three new species of Autocoptis are 

Hickman, Carole S. 1976. Bathyal Gastropods of 
the Family Turridae in the E^arly Oligocene 
Keasey Formation in Oregon . . . Bull. Amer. Pa- 
leontology, vol. 70, no. 292, 119 pp., 7 pis. 

Iversen, E. S. 1977. Farming the Edge of The 
Sea. 436 pp., 202 text figs. Fishing News Books 
Ltd., 1 Long Garden Walk, Famham, Surrey, 
England. $23.00. This is a greatly improved 
and enlarged second edition of a very in- 
formative and accurate book on the mari- 
culture of marine organisms, including mol- 

Marincovich, Louie, Jr. 1977. Cenozoic Nati- 
cidae (Mollusca: Gastropoda) of the North- 
eastern Pacific. Bull. Amer. Paleontology, vol. 
70, no. 294, 494 pp., 42 pis. An excellent 
systematic, paleontological and biogeographical 
treatment of 18 genera, 87 species, of Cenozoic 
naticids from the Eastern Pacific. The family 
Choristidae Verrill 1882 is now synomymized 
with Polinicinae Finlay and Marwick, 1937. 

Cain, A. J. 1977. Variation in the spire index of 
some coiled gastropod shells, and its evolu- 
tionary significance. Philos. Trans. Royal Soc. 
London, Biol. Sci., vol. 277, no. 956, pp. 377-428. 

Yonge, C. Maurice 1977. Form and evolution in 
the Anomiacea—Pododesmus, Anomia, Patro, 
Enigmonia (Anomiidae): Placunanomia, Pla- 
cuna (Placunidae Fam. Nov.). A magnificent 
anatomical analysis of a complex group. The 
family name, Placunidae, however, dates from 
J. E. Gray, 1840. Placunanomiinae Beu, 1967, is 
a synonym. 

Habe, Tadashige. 1977. Systematics of Mollusca in 
Japan. Vol. 1, Bivalvia and Scaphopoda. 372 
pp., 72 pis. of drawings. A much-expanded and 
up-dated checklist, with synonyms, English to 
Japanese glossary, and index. About $20.00 


Several complete original 

sets of 

Johnsonia, vol. 1 to vol. 5, no. 50 $130 each; | 

postpaid (unbound). 

Several incomplete sets (pt. 5 absent) of 

Dall's Tertiary Fauna of Florida, 1890-1895 

(Gastropods and some bivalves). 

Send for 

price list. 

Write: Dept. G., The Nautilus, 

Box 4208 

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Rare and Exotic Specimen Shells 
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^3.00 each 

No orders will be accepted after August 1. 1977 

handsomely bound, gold stamped— 
full color photographs — fine engrav- 
ings and space enough to keep a record of 
everything you plan to do in 1978 Winner of 
many mapr awards, the 1978 diary will again 
emphasize shells as a constantly recurring 
theme in the culture of mankind^ 

'Plus appropriate stale and local sales taxes 

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. __ lor _ 

.copy(ies) of me 1978 Shell Desk Diary 

Mail your order to Stiell Oil Company, One Stiell Plaza, Houston, Texas 77001 
room 1 536 The Diary will be mailed to you in November (2) 


_ State _ 






1 Historical hy C. M. Yonfie 

2 The nature of molluscs by C. M. Yonge 

3 Classihcation by C. M. Yonge 

4 Chitons by C. M. Yonge 

5 The first gastropods by C. M. Yonge 

6 Limpets and top shells by C. M. Yonge 

7 Mesogastropods hy C. M. Yonge 

8 Mesogastropods — burrowers and drifters by C. M. Yonge 

9 Neogastropods — scavengers and predators by C. M. Yonge 

10 Opisthobranch sea-snails hy T. E. Thompson 

1 1 Sea slugs hy T. E. Thompson 

12 Origin and nature of bivalves hy C. M. Yonge 

13 Evolution and adaptation of bivalves by C. M. Yonge 

14 Ark shells, mussels, fan and file shells, scallops and oysters 

hy C. M. Yonge 

15 Shallow and deep burrowing bivalves by C. M. Yonge 

16 Borers in rock and timber hy C. M. Yonge 

17 Anomalous bivalves and scaphopods by C. M. Yonge 

18 Cuttlefish, squids and octopods hy C. M. Yonge 
Epilogue by C. M. Yonge 

Selected book list 


C. M. Yonge and T. E. Thompson 

An Understandable 
Biology Text 

"The first modem book on the biology of marine mollusks 
that is oi textbook quality, yet so beautifully written 
and illustrated that the legions of amateur conchologists 
will readily absorb its wealth of information"—/?. Tucker 
Abbott. Ph.D. 



Cldthbound, 288 pp., 162 text figures. 16 plates with 18 
marine molluscs. Only $13-96 

glorious color photographs of 

Send check or money order to 
Amenam Matacotogisti. Publ 

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Greenville. De 19807 USA 


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It is becoming increasingly important for 
future research purposes that an identified sam- 
pling of species mentioned in publications be 
deposited in a permanent, accessible museum 
specializing in mollusks. This is particularly 
true of mollusks used in physiological, medical, 
parasitological, ecological, and experimental 

The Delaware Museum of Natural History 

has extensive modem facilities and equipment 
for the housing and curating of voucher 
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this permanent curating service, and catalog 
numbers, if desired, will be sent to authors 
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OCTOBER 27, 1977 



Vol. 91 
No. 4 

A quarterly 

devoted to 

malacology and 

the interests of 



Founded 1889 by Henry A. Pilsbry. Continued by H. Burrington Baker. 
Editor-in-Chief: R. Tucker Abbott 



Dr. Arthur H. Clarke. 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 1 0024 

Mr. Morris K. Jacobson 

Department of Living Invertebrates 

The American Museum of Natural History 

New York, New York 1 0024 
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, Mas.sachusetts 02543 

Dr. Donald R. Moore 

Division of Marine Geology 

School of Marine and Atmospheric Science 

1 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. GUbert L. Voss 
Division of Biology 

School of Marine and Atmospheric Science 
1 Rickenbacker Causeway 
Miami, Florida 33149 

Dr. Charies B. Wurtz 
3220 Penn Street 
Philadelphia, Pennsylvania 19129 


Dr. R. Tucker Abbott 

American Malacologists, Inc. 

Box 4208. Greenville, Delaware 19807 

Mrs. Horace B. Baker 

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Volume 91, Number 4 - October 27. 1977 


The editorial office of The Nautilus after November 15, 1977, will be P.O. Box 
4208, Greenville, Delaware. 19807. All editorial correspondence should be addressed 
to Dr. R. Tucker Abbott, Editor, at that address. The address of the business office 
remains the same. 


Donald R. Moore ..„ 

Small Species of Nuculidae(Bivalvia) from the Ti-opical Western Atlantic ns^ 

Richard H. Bailey 

Varworhula chowanemis. a New Species (Bivalvia: Myacea) ^^ 

from the Pliocene of North America 

Carl C. Christensen and Walter B. Miller 

Two New Rabdotus (Pulmonata: Bulimulidae) from Baja California, Mexico i'^' 

David Mook 

Studies on Fouling Invertebrates in the Indian River, Florida. 

2: Effects of Modulus modulus (Prosobranchia: Modulidae) ^^ 

Thomas H. Dietz and Edward M. Stern 

Seasonal Changes in Reproductive Activity and Biochemical Composition of 

the Fingernail Clam. Sphaemm transvermm ' 

Raymond W. Neck .„ 

Introduced Land Snails of Travis County, Texas 

A. Byron Leonard ^ .„ 

Three New Pulmonate Gastropods from the Late Tertiary of New Mexico i'*'^ 

Alan Solem 

RfuiwdL^cus hubnchti Branson, 1975, a Synonym of Stnatura (S.)pugeienm 

(Dall, 1895) (Pulmonata: Zonitidae) 

Alan Solem 

Shell Microsculpture in Stnatura. Punctum, Radiodincus, 

and Planogifra (Pulmonata) 

News '^^ 



Andrews, Jean. 1977. Shells and Shores of 
Texas, .xx + 365 pp. text figs., 12 colored 
photos. University of Texas Press, Austin, TX. 
78712. $19.95 ($24.95 after Dec. 31, 1977). This 
is a greatly improved second edition of S-a 
Shells of the Texas Cocuit, and now qualifies 
as the best hook on marine mollusks of any 
state. The hook has been reset and much new- 
material added. It will .serve for years as an 
excellent guide to shore conditions and shells 
of Texas and beaches of neighboring states 

McMillan, Nora F. 1977. TJie Observer's Book of 
Seojihells of the British Isles. 158 pp., 195 te.vt 
figs., 8 colored pis. Frederick Warne, Ltd., 
London. About one of the smallest (3' 2 x 6 
inches) hardback guides to shells ever pub- 
lished. Worth taking on field trips in the 
British Isles and northern France. $2.00. 

Jacohson, Morris K. and William K. Emerson. 
1977. Wonders of Starfish. 80 pp., illus. Dodd, 

Mead & Co., N. Y. $4.95. 
coverage for 10-year olds and up. 

An excellent 

(iastropodia. Edited by Glenn R. Webb. vol. 1, 
no. 10, pp. 97-112, pis. 42-46. Six articles on 
anatomy, hybridization and sexolog>' of North 
American land pulmonates. Index to vol. 1. 
Published May 22, 1977. 

Jewell, ('. B. 1977. 'Hie Inception and A.'ircnsion 
if Man. 93 pp. Hardback. Vantage Press, N. 
Y. Mentioned only because the author 
theorizes that man descended from mollusks. 
This should make malacologists feel special. 

Powell, A. W. B. Shelh of New Zealand. Fifth 
revised edition. 153 pp., 45 pis. (2 in color). 
Hardback. Whitcoulls Ltd., N. Z. Checklist of 
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Vol. 1)1(1) 

October 27, 1977 

'Hie Nautilus Uil 


Donald R. Moore 

University of Miami, 
Rosenstiel School of Marine and Atmospheric Science 


Three small species of NucuMae, two of which are the smallest known 
bivalves, are described from tropical western. Atlantic sediments. Nucula 
calcicola n. sp. is a small, less than 2.0 mm, clam found in calcareous sediments 
over much of the Caribbean region. The other two species are placed in a new 
genus. Condylonucula, with C. cynthiae n. sp. as the tvpe. C. cynthiae, matnre^ 
at around 600 /i, is found in the western Caribbean on atolls off the coast oj 
Nicaragua. C. maya n. .sp., mature at around 500 /a has been found at Cozumel 
and Arrowsmith Bank at the northwestern extremity of the Caribbean. Recent 
and Upper Cenozoic Nuculidae of the area are listed, and some are discussed. 

A very small shallow-water species of Nucula 
is widely distributed throughout much of the 
Caribbean region. Specimens, when found, have 
apparently been identified as juvenile N. prorima 
Say or as A^. aegeensis Jeffreys. However, N. 
proxima is a temperate species with a distribu- 
tion from New England to Texas, and is a much 
larger species reaching a size of 10 mm. The 
small tropical species does not reach, at least in 
the material at hand, more than a length of two 
mm. A^. aegeensis. in the western Atlantic, was 
identified by Dall in 1886, and this identification 
has not been challenged even though A^. aegeeyisis 
was described from the Mediterranean. While 
most of the material ascribed to the species came 
from depths of more than 200 m, Dall (1889) gave 
a depth range of 5-464 fins (9-849 m). Later, Dall 
and Simpson (1901) reported a single worn juve- 
nile valve from Mayaguez Harbor (Puerto Rico). 

The American specimens of A'^. aegeensis. ac- 
cording to Dall, are fairly large, reaching a 
length of more than 10 mm. Dall did not give size 
or locality for the shallow water specimens, and 
apparently no one has studied them recently. 
Dall apparently considered small Nucula from 
shallow water to be either A^. proxima or A^. 

'Contribution from the University of Miami. Rosenstiel 
School of Marine and Atmospheric Science, and Contribution 
No. .5 from the West Indies Laboratory, Fairleigh Dickinson 

aegeensis. This was probably due to the amount 
and condition of the material that he had to 
study. He apparently did not have any of the 
rather distinctive species from northern South 
America at the time. South Caribbean shallow 
water species are Nucula dalmasi Dautzenberg 
1900, N. Surinam ensis Altena, 1968, and A''. 
venezuelana Weisbord, 1964. 


I first found the new species in a bottom sam- 
ple collected at a depth of two m in Lameshur 
Bay, St. John, U. S. Virgin Islands (Moore, 1970). 
Thinking that these were very young specimens, I 
did not attempt to identify them at the time. 
Several years later, I found more specimens in 
bottom samples from Serrana Bank (Bock and 
Moore, 1971), an atoll in the western Caribbean 
(Milliman, 1969). It was not until I found that I 
had 72 specimens from two stations made at 
Courtown Cays, a small atoll east of Nicaragua, 
that I became convinced that I had a small 
shallow-water-dwelling species. The largest 
specimen measures 1.90 mm. 

By this time I had also found several 
specimens of a much smaller species with a 
peculiar prodissoconch. This nuculid gave every 
indication of having attained full growth at a 
length of about 600 ji. Naturally, I wanted more 
material before attempting to describe either 

120 The Nautilus 

October 27, 1977 

Vol. 91(1) 

species as there have been many cases of im- 
mature mollusks described as adults, often badly 
misclassified (Moore, 1966, Pilsbry, 1949). Search- 
ing through sediment samples from St. Croix, 
Virgin Islands, Key Largo in the Florida Keys, 
and from Bermuda all provided more material of 
the larger species. 

Bottom samples from Chancanab Lagoon, 
Cozumel, Mexico, collected in November, 1971. 
provided a large suite of the largest species and 
over 30 specimens of another, very small species. 
The latter species was also found in sediments 
from Arrowsmith Bank, a flat topped bank about 
34 km NNE of Cozumel. Since I now had well 
over 300 specimens of the largest species, and 52 
of the two smaller ones, I felt that there was lit- 
tle doubt that all three species matured at a very 
small size. In the following descriptions, the 
largest species is assigned to Nucula. and a new 
genus is erected for the smaller two. 


Genus Nuada Lamarck, 1799 

Type species by monotypy, An-a nucleus Lin- 

Nucula calcicola new species 

Description: A small species of Nucula matur- 
ing at a length of about 1.5 mm. The pro- 
dissooinch is about 220 ^ long, somewhat flat- 
tened, pitted, and has a small knob near the 
posterior edge. The dissoconch is about 25% 
longer than high; thickness of an adult specimen 
is about one half the length. The anterior end is 
extended and rounded; posterior end truncate. 
The posterior margin forms a straight or nearly 
straight line. The ventral margin is well-rounded 
and weakly dentate. Both concentric and radial 
sculpture are present, but are exceedingly weak. 
A thin brownish periostracum is present on fresh 

The resilifer is internal, short, and nearly at 
right angles to the hinge line. The anterior limb 
of the hinge is broad, and is widest distally be- 
tween the two teeth. Mature specimens us- 
ually have seven anterior teeth in the left valve, 
six in the right. The posterior limb of the hinge is 
short and broad with four teeth in the left valve, 

four in the right. The adductor muscle scars are 
located at each end of the hinge. Shell structure 
in fresh specimens is transparent; there is no 
nacre, or at most, an extremely thin wash of this 

Material: Holotype. Specimen collected alive, 
1.74 mm long and 1.38 mm high. U. S. N. M. No. 

Type locality: Chancanab Lagoon, depth 2 m, 
Cozumel, Quintana Roo, Mexico. 

Paratyj)es and other localities: Courtown Cays, 
western Caribbean, Lagoon, depth 11 m, 59 
separate valves. North end of the atoll, depth 2 
m. 13 separate valves. Serrana Bank, western 
Caribbean: Lagoon, 14 valves, 2 complete spe- 
cimens. St. John, Virgin Islands: Lameshur Bay. 
depth 2 m, 15 separate valves. St. Croix, Virgin 
Islands: West side of Cottongarden Point, depth 1 
m. one valve. Tague Bay, depth 3 m, 3 valves 
and one complete specimen; depth 4 m, one com- 
plete specimen; station at inside edge of outer 
reef, 4 m, 3 valves and one complete specimen. 
Glovers Reef, Belize (British Honduras): depth 2 
m, 3 valves, 2 complete specimens. Cozumel, 
Quintana Roo, Mexico: Chancanab Lagoon, depth 
2 m, 74 complete, 98 separate valves, and 14 
identifiable fragments: depth 5 m, one valve. Key 
Largo, Florida: Harry Harris Park, depth 2 m. 2 
complete, 17 separate valves, some badly broken. 
Andros Island, Bahamas: one mile east of Wax 
Cut. depth 3 m, one complete specimen. Har- 
rington Sound, Bermuda: notch at 4.6 m, 2 com- 
plete, 3 separate valves. 

The paratypes range in length from 0.38 mm. 
for a complete specimen from Cozumel to 1.90 
mm for a single valve from the same locality. 
One typical complete mature specimen from 
Cozumel measured 1.60 long by 1.24 mm high by 
0.86 mm thick. 

Paratypes have been placed in the following 
institutions: National Museum of Natural His- 
tory. Smithsonian Institution (USNM 7585;?7); 
Delaware Museum of Natural History (DMNH 
120581); Academy of Natural Sciences Phil- 
adelphia (ANSP 344387); American Museum of 
Natural History (AMNH 18:^57); Museum of 
Comparative Zoology (MCZ); British Museum 
(Natural History); Rijksmuseum van Natuurlijke 
Historie, Leiden; Laboratoire de Malacologie. 

Vol. 91 (4) 

October 27, 1977 

The Nautilus 121 

Museum National d'Histoire Naturelle, Paris: 
University of Miami Marine Laboratory Museum 
(UMML 28-2812). 

Name: From calcis. lime, and cnla. dweller in, 
referring to the calcareous sediments the new 
species seems to prefer. 

Remarks: At first I thought that A^. calcicola 
should go into Pronucula Hedley, 1902, but I 
could not find any character in the new species, 
except lack of nacre, that was actually distinct 
from other species of Nucula. The one character 
that seems to set Pronucula off from other genera 
is the large smooth area surrounding the um- 
bones, with the sculptured area coming in 
relatively late. Both N. venezuelana Weisbord, 
1964, from the lower Caribbean and A^. eiigua 
Sowerby, 1833, in the eastern Pacific, have this 
feature, but no one has assigned these species to 
Pronucula. Furthermore, a species dredged by me 
in 45 m off Abidjan, Cote d'lvoire, looks like a 
Promicula with a size of 1.0 to 1.5 mm. The large 
prodissoconch, the arched hinge, and the teeth 
distant from the resilifer are all characters used 
by Hedley in forming his new genus. However, 
the largest specimen is 17 mm long, and has the 
characters of a typical Nucula. The above men- 
tioned characters for Pronucula thus appear to be 
juvenile characters, at least in some species. 
Whether P. decorosa Hedley and its allies in 
Australian waters are described from immature 
specimens or are adults, I do not know. 

The collection of 330 specimens of A^. calcicola 
with a maximum size of 1.90 mm from nine 
localities in the western Atlantic left little doubt 
this was a distinct small species of Nucula. The 
only locality where a different Nucula was col- 
lected along with the new species was at Glovers 
Reef, Belize, where two specimens of another, 
perhaps undescribed, species were collected. 
Large specimens of N. calcicola (1.4 to 1.9 mm) 
were examined for signs of maturity, and in this 
material a thickening on the inside of the valves 
was noted as well as some irregularity of the in- 
ner surface. 'Rie adductor muscle scars were 
sunken, indicating that shell material had been 
deposited on the inner surface after growth had 
been completed. However, this is not the smallest 
species of Nucvla. For instance, Powell (1939) 
described Austronucula schencki whose length 

was 1.15 mm, and recently Marincovich (1973) 
described a 1.12 mm species as Nucula interfluc- 
ta. Marincovich had more than 2,(XX) specimens. 

The range of A', calcicola now extends from 
Courtown Cays and Serrana Bank, atolls off the 
coast of Central America, to Belize, to C^izumel 
off the east coast of Yucatan, and the Florida 
Keys. Far to the eastward, it is found in the 
Virgin Islands, and it almost certainly must live 
in the Greater Antilles between the two areas. It 
has also been collected at Bermuda. 

This appears to be a very shallow-water- 
dwelling stenohaline species. All of the known 
localities are around coral reefs, in lagoons 
behind reefs, or where at least a few corals are 
living. Chancanab Lagoon, where N. calcicola was 
most abundant, is a small shallow landlocked 
hjdy of water, Moore (1973), but it is connected 
with the open sea by a short underground pas- 
sage. Several coral colonies were observed grow- 
ing on rocks in the lagoon, and the other animals 
observed were all marine in habitat. 

The greatest depth of any of the material of A^. 
calcicola was 11 m in the lagoon of Courtown 
Cays. All of the specimens taken at this locality 
were rather worn separate valves making it a 
distinct possibility that the clams had been car- 
ried to that depth by water movement from near- 
by shallows. Live material was only collected in 2 
m at Chancanab Lagoon; the depth range for 
empty valves is one to 11 m. Some of the Key 
Largo material (2m) was very fresh in appearance, 
but none were alive when collected. 

N calcicola has apparently been considered in 
the past to be young A'^. aegeensis Jeffreys. Our 
knowledge of this species in the western Atlantic 
stems mainly from Ball's (1886) discussion. There 
is a brief description of N. aegeensis in Dall and 
Simpson (1901), but it is based on the "one young 
left valve" found at Mayaguez, Puerto Rico, or on 
larger specimens in the U. S. National Museum. 
There is also a brief description and figure of a 
2.7 mm specimen ascribed to N. aegeensis in 
McLean (1951), and another very brief description 
and figure in Warmke and Abbott (1961) of a 
specimen collected in a shallow dredging at Puer- 
to Rico. It is not certain what species these 
specimens represent. It is interesting to note that 
Dall first (1886) reported A^. aegeensis at a depth 

122 The Nautilus 

October 27, 1977 

Vol.!) 1(4) 

range of 175 to 464 fathoms (320 to 849 m). I^ter. 
he dec-ided that shallow water material from the 
shelf off North Carolina also was A^. aegeensis. 
Probably this material should be reexamined. 

At least a dozen Recent species of Nwula have 
been described or reported, from the Caribbean 
region. In the following list, the ma.ximum 
reported size of the species is given, and also the 
known depth range in the Caribbean area. No at- 
tempt has been made to arrange the species ac- 
mrding to the latest classification, or to provide a 

Recent species of western Atlantic Nuculn 
from northern South America to the southeastern 
United States. 

Nucida aegeensis Jeffreys, 1879 

10.7 mm 

9-849 m 

A^. tenuis Montagu. 1808 

10 mm 

320-82.3 m 

A', cremdata k. Adams, ia56 

6 mm 

.5,5-805 m 

A', prorinia Say, 1822 

10 mm 

2-183 m 


5 mm 

.37.5-2013 m 

N. vemlli Ilall. 1886 

5 mm 

.5.38-.3084 m 

N.femnndimie Dall, 1927 

4 mm 

.5.38 m 

A', didmasi Dautzenberg, 19(X) 

6 mm 

22-67.5 m 

A^. surinamenxif: Altena, 1968 

4.5 mm 

shallow water 

A^. venezuelana Weisbord. 196'1 

2.4 mm 

shallow water 

A^. canceUata .Jeffreys, 1881 

4 mm 

1610 m 

A', callieredemmi Dall, 189(J 

12.5 mm 

1610 m 

A', calriaitd n.sp. 

1.9 mm 

1-11 m 

A', ndelrrens-is Smith. 188.5 

(i mm 

715 m 

There are also more than twenty Cenozoic 
fossil species described from various formations 
from Trinidad to the southeastern United States. 
The list as it stands may not be complete as the 
paleontological literature is now enormous. 
Again, no effort was made to revise the classifica- 
tion, but maximum size and presumed age are 
listed. N. venezuelana is listed again since it was 
originally described from the Pliocene, but the 
other species are apparently known only from the 
fossil record. 

Cenozoic fossil species of Nucula from lands 
bordering the Caribbean and Gulf of Mexico are: 

Nucida venezuelana Weisbord, 


2.7 mm 


N. mareana Weisbord, 1964 

4.4 mm 


N. limonenais C,-Ahh. 1881 

3 mm 

? Miocene 

N. moenensvt Cabb, 1881 

3.5 mm 

'.' Miocene 

A^. /»fcpra//a/uGabb, 1873 

7 mm 


N. teniiisndptn Gabb. 1873 

4 mm 


A', trieta (iuppy. 1867 

4.9 mm 


N. hacrata (Iuppy, 1867 

7 mm 


N. orbicetla Olsson, 1922 

11 mm 


N. cahuitenMx Olsson, 1922 

3.5 mm 


N. chipolana Dall, 1898 

4 mm 


.V. chipiitana waltonia 

Gardner. 1926 
A', mmria Dall, 1898 
Af.fap/ina Dall, 1898 
A', pntniaila Dall. 1898 
A', tampae Dall. 1915 
A', dma Gardner, 1926 
A', defuniak Gardner, 1926 
■V. g(uLsdenensi.< Mansfield. 1937 
A', miiratensis Woodring, 1925 
A'. /iiHi Woodring, 1925 

4 mm Miocene 

4.75 mm Oligocene& Miocene 

.3.8 mm Miocene (fig.sp.) 

6 mm Miocene 

7.3mm L.Miocene 

3.5 mm Miocene 

5 mm Miocene 
3 mm Miocene 

4.8 mm Miocene 

8.9 mm Miocene 

All of the 32 other species enumerated in the 
two lists are distinctly larger than A^. calcicola. 
The only Recent species close in size is A^. 
venezuelana, but this species is only known from 
the northern coast of South America, is heavily 
sculptured, and lives in a muddy environment. 
However, immature specimens of one or more 
species could be confused with N. calcicola. 
Material of the unidentified species found with 
N. calcicola at Glovers Reef consists of two right 
valves, 2.2 and 2.64 mm long. This was the only 
station where a similar species was found along 
with A^. calcicola. However, the Glovers Reef 
material, a 4.16 mm right valve from Hook Bank 
(Belize), 13 valves from 19° 14' N., 9r20' W (max. 
size 2.0 mm), and six valves (max size 4.0 mm) 
from a depth of 113.5 m (east of Port Aransas, 
Texas), all agree with N. proxima in having a 
narrow elongate resilifer directed anteriorly. The 
shape and sculpture is similar to that of A^. 
calcicola. but the resilifer of A^. calcicola is quite 
different from A^. proxima and its allies. A record 
of Nucula proxima from Panama, based on 
material collected by Olsson and McGinty, ap- 
f)ears to be an undescribed species. A specimen 
donated to the Academy of Natural Sciences of 
Philadelphia is a single valve measuring about 
2.3 mm in length. 

There are many species in the ancient family 
Nuculidae, and most of these are small simple 
clams without strong characters setting them off 
from other species. Perhaps the most divergent of 
the genera is Acila with divaricate external 
sculpture. Acila is not known from the Atlantic. 
Species in the tropical western Atlantic range 
from smooth to somewhat sculptured, and have 
little diversity of form. Thus identification is 
often difficult, and this is especially true for the 
smaller species. 

Vol. 91 (4) 

October 27, 1977 

The Nautilus 123 

The other new species of Nuculidae herein con- 
sidered are distinctive for several reasons; their 
extremely small size, few hinge teeth, and com- 
paratively large sculptured and pitted prodis- 
soconchs. They appear to be so different from 
other nuculids that a new genus is hereby erected 
to contain them. 

Condylonucula newgenus 

Extremely small nuculids wath a large caplike 
prodissoconch. The valves are inflated, well- 
rounded, and have concentric sculpture. The 
anterior end is longer than the posterior; the pro- 
dissoconch is pitted and sculptured and as much 
as 40% of the length of the dissoconch. Hinge 
teeth few in number, while the resilifer is small 
and more or less normal to the hinge line. There 
is no nacre on the interior of the shell. TTie ad- 
ductor muscle scars are paired, roughly equal in 
size, and the valve margins are smooth. 

T)ff)e species: Condylonucula cynthine, 
new species 

Name: from condylus, a knob on the end of a 
bone, referring to the prodissoconch, and nucida. 
a small nut. Gender: feminine. 

The genus is erected for a pair of species, both 
new, from the western Caribbean. They are 
characterized by the relatively enormous pitted 
and sculptured prodissoconch, few hinge teeth, 
concentric sculpture, and smooth ventral margins. 
TTiey are also smaller than any other species in 
the family. 

(Condylonucula cynthiae new species 

Description: An extremely small species 
maturing at a length of about 600 ^i (0.6 mm). 
The shell is compact, a little longer than high, 
and is rather thick. The prodissoconch is large, 
about 210 fi long, and has a large knob centrally 
located adjacent to the hinge line. There are two 
concentric ridges, an inner one about half way to 
the edge of the prodissoconch, and an outer ridge 
forming the projecting outer edge. Both ridges 
are best developed in the anterior and posterior 
areas, the inner ridge especially so on the pos- 
terior side. The surface of the prodissoconch is 
pitted. The anterior end of the dissoconch is 

well-developed, the posterior end short. The ven- 
tral margin is well rounded. About ten to twelve 
concentric ribs are present on the adult. There 
are fine concentric striae between the ribs. The 
interior of the shell is without nacre. Two oval 
adductor muscle scars are present, the ventral 
margin is smooth, and the hinge plate is short 
and broad. There are four anterior, three pos- 
terior hinge teeth in the right valve, four an- 
terior, two posterior in the left valve. There is a 
slight depression or notch on the inside at either 
end of the hinge. The resilifer is short and almost 
normal to the hinge. 

Name: named for Cynthia Moore, wife of the 

Material: Holotype. Complete specimen 600 ^^ 
long, 480 M high. USNM No. 758534. 

Type locality: About 800 m west of outer reef 
(lagoon) Courtown Cays (Cayos del E.S.E.) in the 
western Caribbean off Nicaragua. Depth, 7.5 m. 

Paratypes: (specimens are complete unless 
otherwise noted). Courtown Cays, depth 1.5 m, 
one 350 m long, one (bored) 600 m long, one 460 f^ 
long, one 460 n long, one 6.30 m long, one broken 
right valve, one fragment, USNM No. 758538. 
Courtown Cays, depth 1.5 m, one 620 ^ long, one 
right valve 560 ^^ long, ANSP No. 344388. Cour- 
town Cays, depth 1.5 m one 570 n long, one left 
valve 620 ^ long DMNH No. 120580. Courtown 
Cays, north end, about two m, one 465 n long, one 
left valve 600 m long, one left valve 580 n long, 
MCZ No. Unknown. Courtown Cays, outer reef, 
one m, one 630 ^ long, one left valve 590 ^i long. 
Serrana Bank, lagoon, one 590 ^ long, UMML No. 

Two specimens from Serrana Bank, one com- 
plete, one a left valve, both 600 ^ long, were lost 
after being photographed with the Scanning Elec- 
tron Microscope at the University of Illinois. 
Hence there were originally eighteen good 
specimens available for this study. 

Remarks: TTie minute size of C. cynthiae makes 
it unlikely that it would be confused with any 
other species of Nuculidae except another new 
species (C. maya) described in this paper 
(for comparison of the two species, see remarks 
after the description of C. maya). The young of 
other species such as C. calcicola may look super- 
ficially like C. cynthiae, but do not have the 

124 The Nautilus 

October 27, 1977 

Vol.91 (4) 

strongly sculptured prodissoconch or show signs 
of maturity. 

Maturity is always a problem when studying 
very small mollusks. TTiere have been many cases 
of a larval or immature shell being described as 
an adult. Externally, one should look for a dif- 
ferentiated prodissfX'onch or protoconch to be cer- 
tain that the sf)ecimen is beyond the larval stage. 
In bivalves, indications of maturity should be 
looked for on the inside of the valves. The shell is 
usually thickened internally after reaching max- 
imum growth, and this is often accompanied by 
irregularities of the inner surface. Adductor mus- 
cle scars become sunken while changes in the 
hinge line may also occur. 

One other species in the family, Nunda 
calcicola, has been found at both Courtown Cays 
and Serrana Bank. At present, these two atolls 
(Milliman, 1969), some 250 km apart, are the only 
known localities for C. cynthiae. A number of 
islands, islets, and shallow banks, however, are 
located off Nicaragua and Honduras, and prob- 
ably have other populations of the species. There 
is also very little information on the vertical 
range of C. cynthiae. All of the specimens were 
collected in quite shallow water 1 to 7.5 m deep. 

Condylonucula tnaya new species 

Description: 1^ is is an extremely small species 
maturing at a length of about 500 n. The shell is 
compact, oval in shape when viewed from the 
side, and moderately thick. 

The prodissoconch is large, 220 fi long, and has 
a small knob centrally located next to the hinge 
line. The edge of the prodissoconch is somewhat 
raised above the adult shell, but does not form a 
distinct ridge. An inner concentric ridge is ex- 
tremely weak or absent on the anterior and me- 
dian area of the prodissoconch, but becomes an 
upright projection on the posterior part. This pro- 
jecting ridge is about the same height as the cen- 
tral knob. The surface of the prodissoconch is pit- 
ted. The dissoconch is oval in side view, and has 
most of the prodissoconch confined to the pos- 
terior half The anterior end is more elongate 
than the posterior; both ends are rounded to 
about the same degree. The ventral margin is 
moderately well rounded, and there are about 10 

to 12 weak concentric ribs. 

The shell is transparent when fresh. Two oval 
adductor muscle scars are present; the ventral 
margin is smooth; and the hinge plate rather 
narrow. Ilie hinge teeth number three anterior, 
two posterior in both valves. The resilifer is a 
short triangular notch beneath the prodissoconch. 

Name: Named for the inhabitants of the 
Yucatan Peninsula. 

Material: Holotype. Complete specimen 500 ji 
long, 380 M high. USNM No. 758536. 

Type locality: Chancanab Lagoon, Cozumel, 
Quintana Roo, Mexico. 

Paratypes: Chancanab Lagoon, depth 2 m. 
Seven complete, 365, 270, 430, 530, 480, 500, and 
480 ^i long; one right valve 500 (i long. USNM No. 
758536. One 540 ^*, one 520 /i, and a right valve 
480 /i long, MCZ No. Unknown. One 460 n, one 
520 fi, one 325 ji, and a left valve 500 fi long. 
ANSP No. 344389. One 460 ^i. one 425 n. and a 
left valve 445 m long, AMNH No. 183858. One 500 
M. one 490 m, one 380 ^, and 510 n long. DMNH 
No. 120579. One 490 m long. Fm (Field Museum) 
No. 198080. 

Five complete sjjecimens ranging from 470 to 
510 fi long, and three separate valves ranging 
from 370 to 465 ^ long have been kept by the 

Arrowsmith Bank, "Gerda" Sta. 899, September 
10, 1967, depth 110 to 220 m, two specimens both 
520 fi long, UMML No. 28-2810. 

Remarks: C. maya is clearly closely related to 
C. cynthiae. The chief differences are: in C. maya 
the prodissoconch is not as strongly sculptured, 
the central knob is weaker, and the dissoconch is 

FIG. 1. Interior view of right valve of holotype of Nucula 

FIG. 2. Exterior view of left I'olve of holotifpe of Nucula 
calcicola. length for both isl.7J,mm. 

FIG. 3. Interior mew of left valve of paratypc of Nucula 
calcicola. This was a large specimen, 1.9 mm long, and s/ioxvs 
signs of old age. irregvlar shelly deposits on the inteior and 
strongly deveUrped hinge. Thissperimen waslaterlost. 
FIG. 4. Ejcterior mew of right vali'e of holotype of 
Condylonucula maya. 

FIG. 5. Interior view of left valve of holotype of Con- 
dylonucula maya, both 500 ^ in length. 

FIG, (i. Exterior view of left valve of holotype of Con- 
dylonucula cynthiae. 

FIG. 7. Interior view of right valve of holotype of Con- 
dylonucula cynthiae, both 600 jj in length. 

Vol. 91 (4) 

October 27, 1977 

The Nautilus 125 



5 -^-^— / 

New NucuMae—D. R. Moore (see explanation on opposite page) 

12fi Tlie Nautilus 

October 27, 1977 


more elongate. Two representative adult speci- 
mens had the following measurements: (In each 
case, the percentage refers to the length of the 




Th ichness 

600 pi 

480 ,i 

380 1* 




.520 p, 

.390 >/ 

280 p< 




C. maya 

Another comparative feature is the concentric 
sculpture. It is stronger in C. cynthiae, and this 
species also has fine concentric striae between the 

C. maya is presently known only from Cozumel 
and Arrowsmith Bank, some 34 km to the NNE 
of Cozumel. The examples from Cozumel are all 
from a depth of two m. The Arrowsmith Bank 
specimens were collected dredging up the steep 
slope of the side of the bank. They were probably 
in sediment that poured over the edge of the 
bank, and, if so, must have been living at a depth 

It is interesting that all known specimens of 
the two species have been found at atolls or 
shallow banks, and not on the continental shelf. I 
have recently examined reef sediment samples 
from Belize. These samples were taken from con- 
tinental shelf reefs, and while rich in micro- 
mollusks, did not contain any Condylonucula. 

Other species of bivalves slightly less than a 
millimeter in length have been described. Usual- 
ly, these descriptions have been based on very 
scanty material, often dredged, and little has 
been done since to ascertain whether these are 
truly mature specimens or only partially grown. 
The smallest of these appears to be Cuna gem- 
mula Turton, 1932, from South Africa described 
as fully grown at 0.5 mm. There was only one 
quite transparent valve which was supposed to be 
quite similar to C. concentriea Bartsch, 1915, but 
not so pointed at the top! It is hardly necessary to 
point out that the validity of this species is ex- 
tremely doubtful. 

There are signs of maturity to look for in 
bivalves. These are: thickening of the shell, 
sunken adductor muscle scars, rugosity of the in- 

terior surface, thickening of the hinge line, and, 
sometimes formation of denticles along the ven- 
tral margin. Even with these guides, one must ex- 
ercise caution, as there is considerable variation 
in the appearance of the adult from one species 
to another. It is best to have a series of spe- 
cimens, preferably from more than one locality, 
so that morphological changes from sub-adult to 
adult can be observed. These changes are some- 
times dramatic although the maximum dimen- 
sions of the shell may be almost unchanged. 


Tlie three species herein described present 
quite a contrast. Nucula calcimla is ubiquitous in 
the Caribbean and adjacent areas, while the two 
species of Condylonucula appear to be confined to 
two small areas in the western Caribbean. All 
three species, however, have only been found in 
calcareous sediments. Information is usually lack- 
ing on ecological requirements of species, but 
Hampson (1971) has shown that A^. proiima Say 
lives in fine to medium quartz sand, and that the 
similar appearing A'^ annulata Hampson lives in 
muddy areas. 

N. calcicola has been found in back reef to 
stenohaline inshore areas in quite shallow water. 
The depth range of the present material is one to 
11 m. but live or fresh material has only been 
found at two meters. C. cynthiae has been found 
only in back reef and lagoonal deposits from one 
to 7.5 m in fairly coarse sediments. C. maya has 
been found in 2 m in quiet water and at 25 to 35 
m (dead material from steep slope). It may well 
be a deeper water species that shuns the turbu- 
lent water of shallow reefs. Chancanab Lagoon, 
however, provides a quiet environment with 
oceanic water, and this seems to prove an ac- 
ceptable niche for C. maya. Chancanab sediments 
are much finer than those in which C. cynthiae 
are found. 

The three species have a number of character- 
istics in common. They are very small (two are 
the smallest known bivalves), and are rather 
similar in appearance. They are stenohaline and 
tropical in distribution. TTiey live in quite 
shallow water, and in areas with calcareous 
sediments. Thus their ecological requirements are 
similar to those of hermatypic reef corals. The 

Vol. 91(1) 

October 27, 1977 

The Nautilus 127 

two species of Condylonuctda especially seem to 
be confined to a very narrow range of physical 
conditions. Their very limited geographic range 
may signify a very brief planktonic larval stage, 
or none at all. 


I would like to thank Gray Multer for the op- 
portunity to collect and study Virgin Island 
raicromollusks. It was because of this material 
that I started working on the small Nuculidae. I 
also thank John Milliman for his invitation to 
take part in the Caribbean Atoll cruise in 1966. 
Thanks are due to Wayne Bock for sorting part 
of the Serrana Bank material in which the first 
two C. cynthixie were found. To Jon Staiger, 
thanks also for the opportunity to participate in 
the Arrowsmith Bank cruise of September, 1967. 
To Peter Supko, thanks for two bottom samples 
from Bermuda. Thanks are also due to Donald 
Marszalek for bottom material from Belize. I also 
thank my wife Cynthia for the trip to Cozumel as 
she discovered the bargain tour that made it 
possible to visit the island. 

Acknowledgment is made to the donors of the 
Petroleum Research Fund, administered by the 
American Chemical Society, for partial support of 
this research (PRF No. 5063-AC2). This work was 
also supported in part by National Science Foun- 
dation Grant GB-8684. 


Adams, A. 1856. Descriptions of thirty-five new species of 
bivalve mollusca (Leda. Nucula, and Pythina) from the 
Cuming collections. Proc. Zool. Soc. London. 185.5: 47-.5.3. 

Altena, C. 0. 1968. The Holocene and Recent marine bivalve 
Mollusca of Surinam. Stud. Fauna Curacao 10: 153-179. figs. 

Bergmans, W. 1968. A survey of the species of the genus Pro- 
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figs. l-6c. 

Bock, W. D. and D. R. Moore 1971. The Foraminifera and 
micromollusks of Hogsty Reef and Serrana Bank and their 
paleoecological significance. Trans. Fifth Carib. Geol. Conf., 
Geol. Bull. No. 5: 143-146. 2 figs. 

Dall. W. H. 1886. Report on the Mollusca. Part I. Brachiopoda 
and Pelecypoda. Report on the results of dredging. . . in the 
Gulf of Mexico (1877-78) and in the Caribbean Sea 
(1879-1880), by the U. S. Coast Survey steamer "Blake". 
Bull. Mus. Comp. Zool. Harv., 12(6): 171-318, pis. 1-9. 

Dall, W. H. 1889. Report on the MoUusca. Part II. Gastropoda 

and Scaphopoda. Reports on the results of dredging ... in 

the CuU of Mexico (1877-78) and in the Caribbean Sea 

(1879-1880) by the U. S. Coast Survey steamer "Blake". 

Bull. A/!«. Comp. Zool. Harv., 18: 1-492, pis. 10-40. 
Dall, W. H. 1890. Preliminary report on the collection of 

Mollusca and Brachiopoda obtained in 1887-88 (Albatross). 

Ptm: U. S. Nat. Mtis. 12(773): 219-.36a pis. 5-14. 
Dall, W. H. 1898. Contributions to the Tertiary fauna of 

Florida. TVon.s. Wagner Free Inst. Sci.. PhUa. 3(4): .571-947, 

pis. 23-a5. 
Dall. W. H. 1915. Monograph of the molluscan fauna of the 

Orthaulax pugnax zone of the Oligocene of Tampa, Florida. 

Bull. USNMW. 1-173, pis. 1-26. 
Dall, W. H. 1927. Small shells from dredgings off the 

southeast coast of the United States by the United States 

Fisheries Steamer "Albatross" in 1885 and 1886. Proc. U. S. 

Sat. Mus. 70(18): 1-134. 
Dall. W. H. and C. T. Simpson. 1901. The Mollusca of Puerto 

Rico. Bull. U. S. Pish Comm. 20: .351-516, pis. 53-58. 
Dautzenberg, Ph. 1900. Croisieres du yacht Chazalie dans 

I'Atlantique. Mollusques. Mem. Soc. Zool. France 13: 

145-265, pis. 9-10. 
Gabb, W. M. 1873. On the topography and geology of Santo 

Domingo. Trans. Amer. Philos. Soc.. new series, 15: 49-259, 

2 maps. 
Gabb. W. M. 1881. Descriptions of new species of fossils from 

the Pliocene clay beds between Limon and Moen, Costa 

Rica, together with notes on previously known species from 

there and elsewhere in the Caribbean area. J. Acad. Nat. 

Sri. Phila, 2nd series, 8: 349-380. pis. 45-47. 
Gardner, J. 1926. The molluscan fauna of the Alum Bluff 

Group of Florida. Part I. Prionodesmacea and Anomalo- 

desmacea. U. S. Geol. Surv. Prof. Pap. 142A: 1-64. pis. 1-15. 
Guppy. R. J. L. 1867. On the Tertiary fossils of the West In- 
dies with special reference to the classification of the 

Kainozoic rocks of Trinidad. Proc. Sri. Assoc. Trinidxid. Part 

3: 145-176. 
Hampson. G. R. 1971. A species pair of the genus Nucula 

(Bivalvia) from the eastern coast of the United States. Proc. 

Malac. Soc. London 39(5): .3.33-342, 1 pi.. 3 figs. 
Hedley, C. 1902. Scientific results of the trawling expedition 

of H.M.C.S. "TTietis" off the coast of New South Wales in 

February and March 1898. Mollusca, Part I, Mem. Aust. 

Mus. 4: 287-321. figs. .39-60. 
Jeffreys. J. G. 1879. On the Mollusca procured during the 

"Lightning" and "Porcupine" expeditions. 1868-70. (Part 2). 

Prw. Zool. Soc. London, 1879: 553-588, pis. 45-46. 
Mansfield, W. C. 1937. MoUusks of the Tampa and Suwannee 

limestones of Florida. Bull. Flo. Ceol Surv. 15: 1-.3.34. pis. 

1-23, 10 figs. 
Marincovich, L. 1973. Intertidal mollusks of Iquique, Chile. 

Los Angeles Co. Mus. Nat. Hist. Sri. Bull. 16: 1-49, 102 figs.. 

1 map, 1 table. 
McLean. R. A. 19.51. The pelec>T»ds or bivalve mollusks of 

Puerto Rico and the Virgin Islands. Sclent. Sun: P. Rico. 
N. Y. Acad. Sci. 17(1): l-ia3, 26pls. 
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Courtown Cays, Alburquerque Cays, Roncador and Serrana 

Bank. Atoli Res. Bull. No. 129: i-iv. 1-26, 29 figs. 

128 The Nautilus 

October 27, 1977 

Vol. 91(1) 

Montagu. G. 1808. Testacea Britannica: or an account of all 

the shells hitherto discovered in Britain. Suppl. i-iv, 1-18;3. 

pis. 17-30. 
Moore, D. R. 1966. The Cyclostremellidae, a new family of pro- 

sobranch mollusks. Bull. Mar. Sci. 16(3): 480-484. 6 figs. 
Moore. D. R. 1970. A new Caecum from Pureto Rico and the 

Virgin Islands. Bull. Mar. Sa. 20(2): 368-373. 
Moore. D. R. 1973. Mollusks from a small landlocked Mexican 

lagoon. Bull. Amer. Malac. Unwn 1972: 5-6. 
Olsson. A. A. 1922. The Miocene of Northern Costa Rica, with 

notes on its general stratigraphic relations. Rilt. Amer. 

Pa/po,9(.30): 1-310. pis. 1-32 
Olsson. A. A and T McGinty 1958. Recent marine mollusks 

from the Caribbean coast of Panama with the description of 

some new genera and species. Bull. Amer. Paleo. 39(177): 

1-58, 5 pis. 

Pilsbry. H. A. 1949. Dissentnma. the embryonic stage of 

Cymalium martuiianum {Orh.) The \autilus 62Hy. 142. 
Powell. A. W. B. 19,39. The Mollusca of Stewart Island, Rec. 

Auckland hist. & Mu^ 2: 211-238, pis. 48-.50. 
Say, T. 1822. An account of some marine shells of the U. S. J. 

Acad. Nat. So. PkUa.. 1st ser., 2: 257-276. 
Turton, W. H. 1932. The marine shells of Port Alfred. S. 

Africa. Oxford Univ. Press, i-.wi. \-Xi\. 70 pis. 

Warmke, G. L. and R. T. Abbott 1961. Caribbean Seashelts. 
Livingston Publishing Co.. Narberth. Pennsylvania, 348 pp, 
44 pis.. 34 figs. 

Weisbrod, N. E. 1964. Late Onozoic pelecypods from northern 
Venezuela. Btdl. Amer Paleo. 45(204): 1-.564. pis. 1-.59. 

Woodring. W. 1925. Miocene mollusks from Bowden. Jamaica. 
Carnegie Inst., Washington Publ. No. 366; 1-222. pis. 1-28. 


Richard H. Bailey 

Dept. of Earth Sciences 

Northeastern University 

Boston, Mass. 02115 


Varicorbula chowanensis n. sp. occurs in the late Pliocene deposits along the 
Chowan River of northeastern North Carolina. This i,s the first report of the 
genus in the Neogene Chesapeake Group of Virginia and North Carolina. 

Late Pliocene deposits along the Chowan River 
in northeastern North Carolina contain diverse 
molluscan assemblages that are indicative of 
shallow shelf and estuarine environments. Within 
these assemblages the family Corbulidae is rep- 
resented by Caryocorhida inequalis (Say), C. cf. 
conradi Gardner, and Varicorbula chowanensis n. 
sp. The genus Varicorbula has not been reported 
from well-exposed late Miocene and Pliocene 
strata of the Chesapeake Group of Virginia and 
northern North Carolina; however, specimens of 
Varicorbula, labeled V. caloosae (Dall), from the 
Pleistocene Waccamaw Formation of south- 
eastern North Carolina are in the collections of 
the United States National Museum. 

Varieorbula is unique in that it exhibits the in- 
equivalved condition of the Corbulidae to a very 
high degree. Tlie right valve is extremely convex 

and bears coarse concentric rugae. The smaller 
left valve is flatter and bears concentric growth 
lines crossed by irregular radial riblets. Yonge 
(1949) demonstrated that Varicorbula gibba 
(Olivi) lives with the plane of the commissure 
vertical despite the asymmetry of the valves. He 
suggests that the large overlap of the valves may 
allow the animal to compress water in the man- 
tle cavity periodically to expel pseudofeces. The 
inhalent siphon of V. gibba is flush with the sedi- 
ment surface so that when the clam is actively 
pumping, large quantities of fine sediment, along 
with diatoms, bacteria, and organic detritus are 
carried into the mantle cavity (Yonge, 1949). In 
order to utilize such a food resource Varicorbula 
needs an effective mechanism to dispose of the 
sediment accompanying the food. Varicorbula 
chowanensis also lived in bottoms consisting of 

Vol. 91 (4) 

October 27. 1977 

The Nautilus 129 


FIG. 1. Exteriw of hohtype (USNM m806) of Varicorbula 
chowanensis n. sp.. right valve, length 7.2 mm (a): left valve, 
paratype (USNM 2i 1807), length 6.9 mm (b); interior of right 
valve (c): interior of left valve (d). 

Interior of right valve with a very faint pallial 
line and small pallial sinus; with well-developed 
marginal groove for insertion of left valve; ad- 
ductor scars small, slightly impressed and closest 
to dorsal valve margin; single conical cardinal 
tooth below and slightly anterior of beak; deep 
subumbonal resilial pit. Interior of left valve 
shows pallial line; adductor scars poorly-de- 
veloped; small thick chondrophore immediately 
beneath and posterior of beak is firmly fused to 
hinge plate; immediately anterior of chondro- 
phore and beneath beak is a large socket for the 
cardinal tooth of the right valve. 

very clayey and silty fine sands. It is likely that 
the function of the valves hypothesized by Yonge 
(1949) also operated for the extinct species, V. 

Family Corbulidae Lamarck, 1818 

Genus Varicorbula Grant and Gale, 1931 

Varicorbula chowanensis new species 

(Figs. 1, 2) 

Description: Shell small, very strongly ine- 
quivalve; right valve convex and inflated with 
high prosogyrate umbo, rounded anterior, trun- 
cate posterior, flat corselet separated from rest of 
valve by poorly defined posterior diagonal ridge 
and abrupt anterior turn of concentric ribs; left 
valve flatter and smaller than right, narrow well 
defined umbo, rounded low posterior ridge defines 
irregular corselet, rounded anterior, sub-truncate 

Sculpture of right valve consists of regularly- 
spaced, rounded concentric ribs, becoming higher 
and wider near ventral margin; prodissoconch 
devoid of sculpture. Exterior of left valve with ir- 
regular concentric grooves parallel to the growth 
lines; distinct but frequently irregular growth 
lines are crossed by faint discontinuous riblets 
that converge toward the umbo; riblets 3 to 8, 
with highly variable spacing, and are more 
distinct on ventral portion of valve. 

FIG. 2. Valve outlines of Neogene species o/ Varicorbula; V. 
caloosae (Doll), early Pleistocene Caloosahatchee Formation, 
(a) right valve, length mm, fb) left valve, length 8.6 mm, 
after Olsson arid Harbison (1953); V. chowanensis n. sp., late 
Pliocene "Yorktown" Formation, (c) right valve (USNM 
21,1812). length 7.0 mm, (d) left, valve (USNM 21,1815), length 
7.0 mm; V. waltonensis (Gardner), middle Miocene Shoal 
River Formation, (e) right valve, length 7.5 mm. (f) left valve, 
length 6.5 mm, after Ckirdner (1928); V. chipolana (Gardner), 
lower Miocene (Jhipola Formation, (g) right valve, length 6.5 
mm, (h) left valve, length 5.8 mm. after Gardner (1928). 

130 The Nautilus 


Holotype (USNM 241806) R 

Paratypes (USNM ail8fl7) L 

(USNM 2-1 MIX) R 

(USNM msm) R 

(USNM 241810) R 

(USNM •211811) R 

(USNM 211812) R 

(USNM 241813) L 

(USNM 211814) L 

(USNM 211815) L 

October 27, 1977 

Vol.91 (4) 







No. No. 
Ribs Riblels 




tion, 2.0 kilometers upstream (north) of bridge 
where U. S. Route 17 crosses Chowan River, Ber- 
tie County, North Carolina, locality 27 of Bailey 

Twes: Holotype, right valve, USNM 241806, 
ventral margin partially broken; figured para- 
type, left valve, USNM 241807, measured and/or 
figured USNM paratypes, 241808-241815; undes- 
ignated paratypes, 3 fragmentary valves. USNM 


Varicorbnla chowanends is most similar in 
shape to V. caloosae (Dall, 1898). However, it may 
be distinguished from the latter by its smaller 
size, more gently sloping anterior and posterior 
dorsal margins, narrower umbonal region, and its 
broader, more distinct posterior region (Fig. 2). 
The Vancorbida lineage of the Neogene of the 
Atlantic and Gulf Coastal Plains is represented 
by at least four species (Fig. 2). Varicorbula 
chipolana from the lower Miocene Chipola For- 
mation is the earliest reported member of the 
lineage. The evolutionary relationships of these 
species remains to be clearly demonstrated. 

T]ff)e locality: Pliocene deposits along the west 
bank of the Chowan River, "Yorktown" Forma- 


Bailey, R. H. 1973. Paleienviriinment, paleoecology and 

stratigraphy of molluscan assemblages from the Yorktown 

Formation (upper Miocene— lower Pliocene) of North 

Carolina. Ph.D. dissertatmn. University of North Carolina. 

110 pp. 
Gardner, J. 1928. The molluscan fauna of the Alum Bluff 

Group of Florida. Part V. U. S. Geological Survey Prof. 

Paper 142 E. pp. 185-249. 
Dall. W. H. 1898. Contributions to the Tertiary fauna of 

Florida. Part IV. Trans, of the Wagner Free Inst, of Sri.. 

PhUadelph m. pp. 511-947. 
Olsson, A. A. and Harbison, A. 19.53. Pliocene mollusca of 

Southern Florida. Acad. Nat. Sci. Phila. Man. 8. 4.57 pp. 65 

Yonge, C. M. 1946. On the habits and adaptations of Ahidis 

(Corbulaj gibba. Jour. Marine Biol. Assoc. United Kingdom 

26: :358-376. 


Carl C. Christensen and Walter B. Miller 

Department of General Biology 
University of Arizona 
Tucson, Arizona 85721 


Tira ncir of the land snail genus Rabdotus are described from Baja 
(alifiiniia Siir. Mr.riro. R. gigantensis is reported from the Sienv de la (riganta 
and R. laevapex is reported from Isla Cerralvo. 

The bulimulid genus Rabdotus contains most of 
the larger land snails of Baja California Sur, 

Mexico. Although snails of this genus also inhabit 
much of mainland Mexico and of the southern 

Vol. 91 (4) 

October 27, 1977 

The Nautilus 131 

FIG. 1 and 2. Rabdotus gigantensis Christensen arid Miller, 
neir species. San Javier. Baja California Sur. Mexico. 
Holotj/pe. CASGTCNo. 57937. Shell height 19.7 mm. 
FIG. 3. Rabdotus gigantensis Christensen and Miller, new 
species. Shell opened to show columellar lamina. Paratype. 
CASGTCNo. 579U. Shell height 20.5 mm. 

FIG. 4 and 5. Rabdotus laevape.\ Christensen and Miller, 
new .species. Isla Cerraho, Baja California Sur, Mexico. 
Holotype. CASGTCNo. 579J,2. Shell height 27.8 mm. 
FIG. 6. Rabdotus laevapex Christensen and Miller, new 
species Shell opened to show cohimellar lamina. Paratif})e. 
CASGTCNo. .5794.3. Shell height 28.J, mm. 

and southwestern United States, about three 
quarters of the over thirty known species are con- 
fined to the southern half of the Baja California 
peninsula and nearby islands. Tliis report con- 
tains descriptions of two new species from this 
region, one recorded from several localities in the 
Sierra de la Giganta, the principal mountain 
range of the central part of the peninsula, the 
other known only from Isla Cerralvo, the 
southernmost island in the Gulf of California. 

Rabdotus gigantensis Christensen 
and Miller, n. sp. 

Descriptwn. Shell (fig. 1-3) solid, 16.9-21.3 mm 
in height (mean height of twenty adult shells 
from type lot 19.2 mm), 7.8-10.2 mm in diameter 
(mean 8.8 mm), ratio of height to diameter 1.85- 
2.36 (mean 2.17), ratio of shell height to aperture 
length 2.18-2.62 (mean 2.44), whorls .5-7/8 to 
6-7/8 (mean 6.42); spire convex in outline; em- 
bryonic whorls 2 to 2-1/4 in number, rounded, 

132 The Nautilus 

October 27, 1977 

Vol.91 (4) 


with strong regiilar axial riblets the interstices of 
which are crossed by fine spiral threads; post- 
nuclear whorls convex, sutures moderately im- 
pressed; surface of shell weakly shining, sculp- 
ture of early postnuclear whorls of numerous 
weak growth wrinkles which may bear minute 
hyphen-like granules arranged in spiral rows, 
this sculpture becoming obsolete in later whorls; 
color of shell light brown except peristome and 
narrow subsutural band sometimes whitish; last 
whorl slightly inflated, flattened at periphery, 
often ascending slightly at aperture; columellar 
margin of peristome reflected, basal and palatal 
margins weakly reflected, not revolute; termina- 
tions of peristome joined by a thin to moderately 
thick parietal callus; columella with a well- 
developed sinuous lamina located deep within the 
aperture; basal region of shell deeply rimate. 

Soft parts unknown. 

Ti/pe Locality. Baja California Sur, Mexico, at 
San Javier, in a large lava rockslide immediately 
south of the mission, elevation 350-450 m. 

Holotype. California Academy of Sciences 
Geology Type Collection No. 57937. Height 19.7 
mm, diameter 9.3 mm, length of aperture 8.2 mm, 
whorls 6-5/8. Collected by W. B. Miller, 25 Oc- 
tober 1972. 

Paratypes. 46 specimens collected by W. B. 
Miller, 24 October 1971; 53 specimens collected by 
C. C. Christensen, P. N. D'Eliscu, W. B. Miller, R. 
L. Reeder, and D. B. Richman, 25 October 1972. 
Paratypes in the collections of the California 
Academy of Sciences and Delaware Museum of 
Natural History (No. 112458) and in the private 
collections of R. L. Reeder and the authors. 

Additional Paratype Material. Specimens have 
been examined from the following additional 
localities in Baja California Sur; inland of San 
Jose de Magdalena on the road to Guadalupe, 
43.3 km west of the Transpeninsular Highway, C. 
Church, 11 December 1970; 11.3 km north of San 
Jose Comondu, C. Church, November 1969; San 
Jose Comondu, R. J. Drake, July 1953, and V. 
Roth. 15 February 1966; 1.0 km east of San 
Javier, C. Church, 11 December 1970; 15.7 km 
west of San Javier on the road to Santo Domingo, 
C. Church. 12 December 1970; 72.4 km south of 
Loreto and 49.9 km northeast of Villa Insur- 
gentes on Transpeninsular Highway, in lava 

rockslides on south side of arroyo, elevation 275 
m, W. B. Miller. 23 October 1971; road between 
El Obispo and Rancho Tinajitas. I. L. Wiggins, 20 
November 1959. 

Remarks. Rahdotus gigantensis is distinguished 
by its small size, weakly reflected peristome, col- 
umellar lamina, and coloration. R. leins (Dall) is 
similar in overall dimensions and form but lacks 
a columellar lamina; its shell is usually marked 
with dark axial streaks. R. dentifer (Mabille) and 
R. chamberlini (Hanna) are small snails each 
with a columellar lamina but with the peristome 
strongly reflected or revolute. 

Rahdotus giganterms is most often found in 
large talus slides of volcanic rock and is known 
to occur over nearly the entire length of the 
Sierra de la Giganta. Although dead shells of this 
species are common in some localities, no living 
specimens have yet been collected. 

The species is named for the mountains in 
which it lives. 

Rahdotus laevapex Christensen and Miller, n. sp. 

Description. Shell (fig. 4-6) solid, 24.8-28.6 mm 
in height (mean height of eight adult shells from 
type lot 27.7 mm), diameter 11.8-13.4 mm (mean 
12.6 mm), ratio of height to diameter 2.10-2.29 
(mean 2.19), ratio of shell height to aperture 
length 2.08-2.25 (mean 2.18), whorls 5-7/8 to 6- 
3/8 (mean 6.12); spire weakly convex in outline; 
embryonic whorls not readily distinguishable 
from postnuclear shell; first two whorls rounded, 
smooth or with subobsolete axial wrinkles; later 
whorls convex, sutures weakly impressed, surface 
of shell shining or dull, sculpture of weak growth 
wrinkles; color of shell light brown except peris- 
tome and narrow subsutural band sometimes 
whitish, shell sometimes with light axial streaks; 
last whorl inflated, rounded at periphery, not 
ascending or descending at aperture; columellar 
margin of peristome reflected, basal and palatal 
margins reflected and revolute; terminations of 
peristome joined by a thin white or clear parietal 
callus; columella with a strong spiral lamina 
which is prominently visible within the aperture; 
basal region of shell deeply rimate. 

Pulmonary veins and pallial roof between veins 
and hindgut light brown; mantle not marked 
with dark spots. 

Vol. 91 (4) 

October 27, 1977 

The Nautilus 133 

FIG. 7. Rabdotus laevapex Christensen and Miller, new 
species. Genitalia of halotype. Abbreviations: ec epiphallic 
caeaivi; ep epiphallns: pe upper portion nf penit; ps penial 
sheath and lower portion o/ppnis; sd spermathecal diwt: sp 
spemiatheca: va vagina: vd vas deferens. Scale line 10 mm. 

Genitalia (fig. 7) typical of the genus in general 
structure, epiphallus usually greater in length 
than penis or epiphallic caecum, comprising over 
40% (average of 6 specimens) of the combined 
length of these three structures; penis and 
epiphallic caecum approximately equal in length, 
vagina much shorter than penis; dimensions of 
genitalia of holotype (figured): penis 9 mm in 
length, epiphallus 16 mm, epiphallic caecum 9 
mm, vagina 3 mm, spermathecal duct 26 mm. 

T]fpe Locality. Baja California Sur, Mexico, on 
west side of Isla Cerralvo, approximately 0.5 km 
inland of the beach at El Limona anchorage, in a 
small rockslide on the south slope of a narrow ar- 
royo, elevation 50-100 m. Living snails were 
found sealed to small rocks. 

Holotype. California Academy of Sciences 
Geology Type Collection No. 57942. Height 27.8 

mm, diameter 12.2 mm, length of aperture 12.8 
mm, whorls 6. Collected by C. C. Christensen, 8 
August 1974. 

Paratyjns. 7 adult and 5 immature specimens 
collected with the holotype. Paratypes in the col- 
lections of the California Academy of Sciences 
and Delaware Museum of Natural History (No. 
112457) and in the private collections of the 

Remarks. The sculpture of the embryonic 
whorls is the outstanding character of Rabdotus 
laevapex and distinguishes it from all other 
members of the genus. In other Rabdotuj^ these 
whorls bear regular axial riblets; in R. laevapex 
these are smooth or bear only weak wrinkles 
which do not resemble the riblets of other species. 
This condition is not the result of wear, as it is 
found in the shells of live-collected immature 
specimens of 2-1/2 whorls. The name assigned to 
this species refers to its smooth apex. 

Although the shells of Rabdotus lamellifer 
(Pilsbry), R. rimatus (Pfeiffer), and R. spirifer 
(Gabb) resemble that of R. laevapex in size and 
general form, these species differ from the new 
species anatomically; in each of them the penis is 
greater in length than either the epiphallus or 
epiphallic caecum, and the length of the vagina is 
more nearly equal to that of the penis than is the 
case with R. laevapex. 


We wish to thank the individuals named above 
who collected specimens used in this study and 
Mr. Barry Roth of the California Academy of 
Sciences for the loan of material, as well as Dr. 
D. A. Thomson of the University of Arizona and 
Sr. Felipe Maldonado, captain of the yacht La 
Sirena, who provided transportation to Isla Cer- 
ralvo. We also wish to thank Judith A. Chris- 
tensen for assistance with the preparation of the 
figures which accompany this report. 

134 The Nautilus 

October 27, 1977 

Vol. 91 (1) 


David Mook 

Johnson Stience Laboratory 

Harbor Branch Foundation, Inc. 

Ft. Pierce, Florida 33450 


The buildup of fouling invertebrates on tiles placed among seagrass blades is 
considerably less than on tiles placed in adjacent areas devoid of scagi-ass. Snail 
counts and the results of caging experiments suggest that the grazing action of 
Modulus modulus may retard the buildup of folding organisms on surfaces 
within the gr-ass bed,"!. 

Observations on fouling patterns on the Indian 
River lagoon of eastern Florida indicate that the 
accumulation of fouling invertebrates on tiles 
placed among seagrass blades is considerably less 
than on tiles placed in adjacent areas devoid of 
seagrass. The processes responsible for this are 
not know^n but the following mechanisms were 
suspected: (1) large predators may graze more ac- 
tively among the grass blades (a large predator is 
operationally defined here as one which cannot 
go through a 12 mm mesh); (2) rubbing of grass 
blades on the tiles due to wave action may 
mechanically remove newly settled organisms: 
and (3) survival of newly settled fouling 
organisms may be affected by small animals such 
as Modulus modulus Linne, 17-58, a snail that 
often is found locally on grass blades. 

The research presented in this paper was 
designed to experimentally test whether any of 
these mechanisms are responsible for the retarda- 
tion of fouling in the grass beds. 

The study area was located in a seagrass bed 
north of Link Port on the west bank of the In- 
dian River lagoon near Fort Pierce, Florida 
(31.r27' N; 20.9°80' W) (Young et d.. 1976). The 
site consisted of subtidal dense stands of 
Halodule urrightii Ascherson, 1868, interspersed 
with large sandy patches devoid of grass. Small 
.stands of Tfi<dassi(i testudinum Konig, 1805, were 
occasionally present. 
Page charges paid. 

The experimental fouling substrata were 15 cm 
by 15 cm Italian quarry tiles bolted to 50 cm 
lengths of 2.4 cm (4 inch) PVC (polyvinyl- 
chloride) pipe pushed into the sediment. The bot- 
tom edge of each tile was about 1 cm above the 
sediment surface. Treatments are listed in Table 
1. Each treatment consisted of five replicate tiles. 
Treatment results were compared using Stu- 
dent's-t test. To determine the effect of large 
predators, some tiles were set in cages con- 
structed of 12 mm mesh ('4 inch hardware cloth), 
measuring 2 m on a side. In order to test abra- 
sion effects of grass on fouling accumulation, 
some tiles were set in 2 m by 2 m caged and un- 
caged areas from which grass blades were cut at 
the level of the sediment surface. 

Specimens of Modulus modulus were counted 
four times (Table 1) in October and November 
1976 from the smooth side of each tile. Three 
counts were made during the day and one count 
was made at night. The amount of fouling was 
determined by scraping all accumulated grow1;h 

TALBE 1. Comparison of average dry weights of aenimidfi- 
lion of fouling organisms and average numbers of Modulus 
modulus on tiles subjected to various treatments. 


A I'erage number 



Xfixiuhis mttdiiluit 

umaged. in grass 



caged, in grxss 



uncaged, siind patch 



caged, sand patch 



caged, in clipped grass 



Vol. 91 (4) 

October 27, 1977 

The Nautilus 135 

FIG. 1. Rack med tu hold Italian quarry tiles. The screen 
has been removed to show more clearly the rack's structure. 
Ruler is 33 cm in length. 

from the smooth side of each tile, drying the 
scrapings at 80° C for 72 hours and weighing 

The effect of Modulus modulus on fouling was 
tested by placing five tiles in each of two fouling 
racks (Figure 1). Both these racks were covered 
with nylon window screening (1 mm mesh). One 
hundred specimens of M. tnodulus were placed in 
one rack and the other was kept free of this 
species for a control. The racks were suspended at 
a depth of 0.5 m from a float at the Harbor 
Branch Foundation laboratory for about six 
weeks (7 March 1977-22 April 1977). Screens 
were scrubbed with a brush every two days to 
prevent fouling organisms from clogging the 
screens. Coverage by fouling organisms was 
measured by recording all fouling organisms that 
occurred at each of 80 random points (Greig- 
Smith, 1964) on the smooth side of the tile. Points 
that contained no fouling were also enumerated 
in order to quantify uncolonized space on the 


The dominant fouling animals in the grassbeds 
consisted of Balanus eburjieus Gould, 1841, 
Balanus amphitrite Darwin, 1854 and Spirorhis 
sp. These are common fouling sf)ecies in the In- 

dian River (Mock, 1976). Accumulation of fouling 
organisms was significantly (p<.()l) higher 
(t = 6.2610) on tiles set within the sand area than 
on tiles set in the grass area (Table 1). In the 
sjind patch, the tiles within the cage had signi- 
ficantly (p<.01) more fouling (t = 4.85) than tiles 
outside the cage, whereas no significant dif- 
ferences were found between caged and uncaged 
tiles within the grass bed in either clipped 
(t = 1.6485) or undipped (t = 0.4878) areas. These 
differences suggest that large predators are prob- 
ably important grazers of fouling organisms out- 
side the grass but their role may be limited 
within the confines of the grass bed itself, at 
least when the fouling communities are relatively 
young. The identity of the predators was not 
determined; however, the sheepshead, Ar- 
chom.rgits probatdcephalus Walbaum 1792, an 
abundant fish in the Indian River (Gilmore, 
1977), is known to prey on some fouling 
organisms (Mook, 1977). 

No significant difference in fouling accumula- 
tion was recorded between tiles in clipped and 
undipped areas (t = 1.849) (Table 1), indicating 
that the mechanical abrasion of grass blades rub- 

TALBE 2. Comparison of average number of points out of 
80 occupied by various fouling animals on tiles placed in 
racks nith and without Modulus modulus. "Mi organisms" in- 
dicates average number of points without any finding animals 
present. Average number of species is also compared. Each 
rack ctmtainedfive tiles. 





Diplosoma macdonaldi 
Macdonald. 18.59 (T)" 




Perophora vindis 
Verrill, 1871 (T) 




Bug ida neritina 
Unne. 1758 (E) 




Caropeiini tenuissimum 
Cann, 1908 (E) 




Spirorhis sp (P) 




Cmiophium tubes (A) 



10. 16" 

Balanus sp {B) 




"No organisms" 




Average species number 




* Significant to 0.05 level 

" T = tunicate. P = polychaete, E = ectoprocta, A = 
amphipod. B = barnacle. 

136 The Nautilus 

October 27, 1977 

Vol. 91 (4) 

bing across tile surface has no discemable effect 
on settlement of fouling organisms. 

There were significantly (p<.01) greater 
numbers of M. modulus on tiles within the grass 
bed than on those outside the grass bed 
(t = 4.5905) (Table 1). A negative correlation exists 
between the number of snails found on the tiles 
and the amount of fouling (r = 0.71). Tliese obser- 
vations suggest that grazing by M. modulus may 
retard the accumulation of fouling. When speci- 
mens of M. modulus were placed in screened foul- 
ing racks, the amount of fouling buildup by most 
species was reduced (Table 2). 

Dissections of a few Modulus stomachs 
revealed a small crystalline style and diatom 
tests, an indication the Modulus modulus prob- 
ably is a herbivore, feeding on the epiphytic 
algae and detritus which accumulates on surfaces 
within the grass beds (Houbrick, f)ersonal com- 
munication). The grazing action of Modulus 
modulus probably also dislodges newly settled 
larvae of fouling organisms, thus retarding the 
development of fouling. These mechanisms may 
also aid in keeping the surfaces of seagrass blades 
clear of fouling. 


I am grateful to Dr. David K. Young, Mr. John 
DePalma, Dr. Marsh Youngbluth, Dr. Kevin 
Eckelbarger and Dr. Richard Houbrick for their 
helpful comments while I was preparing the 
manuscript, and Ms. Patricia Linley for her help 
in proofreading the final copies. 


Gilmore, R. Grant. 1977. Fishes of the Indian River lagoon 
and adjacent waters, Florida. Bull Ma. State Mus. 22(.33): 
pp. 101-148. 

Greig-Smith, P. 1964. Quantitative plant ecology. Butter- 
worths. London. 256 pages. 

Mook. David. 1976. Studies on fouling invertebrates in the In- 
dian River 1. Seasonality of settlement. Bull. Mar. Sn. 26: 

Mook, David. 1977. Larval and osteological development of the 
sheepshead, Archosargus probatocephalus (Pisces: Sparidae). 
Copeia 1977: 126-ia3. 

Young, David, Martin Buzas and Martha Young. 1976. Species 
densities of macrobenthos associated with seagrass: A field 
experimental study of predation. J. Mar. Res. 34: 577-592. 

Harbor Branch Foundation, Inc., Contribution No. 77. 




Thomas H. Dietz and Edward M. Stern 

Department of Zoology and Physiology 

Louisiana State University 

Baton Rouge, Louisiana 70803 


Vie life span o/Sphaerium transversum in Louisiana i.s about one year. Mature 
adults are reproduetively ynost active during winter (30-^0 young/adult) and least 
active during the summer (0-12) young /adult). During the height of reproductive 
activity 60-70% of the adult dry tissue mass k developing juveniles retained in the 
branchial chamber. There is a seasonal cycle of tissue protein and carbohydrate 
content, which correlates directly mth reproductive activity. 

The fingernail clams of the family Sphaeriidae 
have been studied extensively in terms of life 

histories, reproduction and growth (Foster, 1932; 
Van Cleave et al., 1947; TTiomas, 1959; Heard, 

Vol. 91 (4) 


October 27, 





variation in size and 



in Spkcwrittm tranitvt^rs-um. 





Juven i 




C 1 


April 197it 







2.6 t 








t 1 

3.1 ^ 







i 1 

1.8 i 








t 2 

1.2 t 








: 2 

1.2 i 








- 1 

0.5 i 








t 2 

1.5 i 












1: J 









'. k 







^46. 5 



2.1 t 








t 2 

2.8 i 


April 1975 






- 3 

2.0 t 


a Component index = mg dry/lOOi-mg entire animal wet weight 

b Mean - standard error of mean 

1964, 1965). Many sphaeriids have been noted to 
have a life span of one year (Foster, 1932; Heard, 
1965). However, there have been no attempts to 
determine the biochemical changes associated 
with the growth, maturation and reproductive ac- 
tivities of fingernail clams. The small size of 
many of these species is probably an important 
factor in the relative absence of physiological in- 
formation. Sphaerium transversiim (Say), 
however, attains a size of 16 mm in length and 
up to 500 mg in total wet weight. The local abun- 
dance of this species and its rapid grow1;h and 
maturation make it a good experimental animal 
and offer some insight into the seasonal changes 
of its reproductive activity and biochemical com- 


Sphaerium transversum were collected from 
Bayou Manchac at its intersection with U. S. 

Highway 61 south of Baton Rouge from April 
1974 to April 1975. The animals were collected by 
dip net and the largest members selected and 
transported to the laboratory out of water in 
order to prevent release of juveniles from the 
branchial chamber. Data were obtained from the 
animals within several hours after collection. 
Each animal was blotted dry and its entire 
weight recorded. Ten animals were opened and 
developing juveniles having shells were separated, 
counted and then dried at 85° C to obtain dry 
juvenile weights. Ten additional animals were 
opened and the soft tissue transferred to a test 
tube. Soft tissue and shells were dried overnight 
at 85° C. The dry tissue was digested with 0.5 ml 
20% KOH at 100 ° C for 30 min. The digest was 
diluted with distilled water and total car- 
bohydrate was determined colorimetrically by a 
phenol-sulfuric acid method (Montgomery, 1957). 
The alcoholic precipitation of glycogen was 


138 The Nautilus 

October 27, 1977 

Vol.91 (4) 

eliminated since the direct analysis agreed (± 
4%) with the recovered precipitate. Total tissue 
protein was determined by the method of Lowry 
et al. (19.51). Component indices were determined 
by dividing the dry weight of the component by 
the entire wet weight of the animal and mul- 
tiplying by 100 (Stickle, 1975). All data are e.x- 
pressed as the mean ± one standard error of the 
mean with the number given in parentheses. 
Voucher specimens are deposited in the Delaware 
Museum of Natural History (No. 102016). 


The life span of S transversum in Bayou Man- 
chac is about one year. The adults die off during 
the spring and summer leaving a population of 
new young by late summer (Table 1). In 
September 1974 the larger animals averaged 
50-60 mg total weight and a maximum length of 
8.4 ± 0.2 (N = 10) mm. All of these animals were 
reproductively active. The smallest size range of 
adults that contained embryos with shells was 
5.5-6.5 mm in length. Almost all adult S. 

transversum have developing embryos of from 
0.1-0.2 mm in length which are enclosed in a 
membranous sac or brood pouch in the branchial 
chamber (Thomas, 1959). The number of embrj'os 
within a brood pouch is variable, ranging from 20 
to .30. These early-stage embryos were not among 
those counted unless a fully developed shell was 
evident. Adult S transversum are apparently re- 
producing continuously. As the adults grow dur- 
ing the fall and winter the number of developing 
young, retained in the branchial chamber, in- 
creases to a maximum of about 60. Each mature 
adult was observed to have three arbitrary 
categories of young within the branchial 
chamber. 1) Young juveniles with shells which 
were contained in a brood pouch. These small 
juveniles were less than 0.5 mm in length with an 
average dry weight (at the limit of measurement) 
of 0.05 ± b.Ol (N = 8) mg. 2) Juveniles of larger 
size (0.5-1.5 mm) which were free in the bran- 
chial chamber. 3) Tliose juveniles just prior to 
release (2-3.5 mm) that obtained a maximum 
total dry weight of 1 mg. Although the largest 

T.ABLE 2. Sea.snnal variation in size and component index in Sphnerium tranxvennim. 







3 dry/lOOmg ( 

5nt i re 













April 1974 


^ 17.3" 


















*- 15.9 


















*- 17.0 


















i 7.0 








































































i 16.2 


















i 16.4 


















i 11.5 


















- 14.0 


















t 16.9 
















April 1975 


















a Mean - standard error of mean, sample size was 10 animals. (1) 

October 27, 1977 

The Nautilus 139 

juveniles probably had fully developed gonads, 
they did not have embryos (Gilmore, 1917). 

The juvenile component index (CI) is an 
estimate of the magnitude of reproductive activi- 
ty in the adults (Table 1). During the height of 
reproductive activity the juvenile CI is about 3 
mg dry weight/100 mg total animal weight. More 
revealing, however, is a comparison between ju- 
venile CI and adult tissue CI. Of the adult dry 
tissue, during the winter months, 60-70% is due 
to the combined weights of the developing juve- 
niles (see Tables 1 and 2). In April 1975 the 
juveniles accounted for 87% of the total adult dry 
tissue. This suggests that the majority of the 
adult activities are devoted to reproduction, 
ultimately leading to the death of the adult 
(Heard. 1965). 











10 - 


2 - 







A S N 


FIG. 1. Seasonal changes in weight of Sphaerium transver- 
sum. Each vertical line represents one standard error of the 

Physical factors also may be contributing to 
the adult die-off during the summer months. The 
average dissolved oxygen measured by Winkler 
titration during July - September 1974 was low 
(0.6 ppm O2). In addition the surface water 
temperature during the summer averaged 28° C. 

Table 2 shows the seasonal changes in entire 
weights and component indices of the reproduc- 
tively active animals. The decline in weight in 
the summer of 1974 is probably due to the in- 
creasing death rate of the adult population. 
Although we cannot rule out adult emigration to 
deeper water or burrowing, it is unlikely (Horst 
and Costa, 1975; Gale, 1976). Free-living young 
sphaeriids display a rapid weight gain during the 
first months after release (Mackie et al., 1976). 
This period of growth is evident in S. transver- 
sum during the fall months (Fig. 1). The average 
shell length in February 1975 was 13.5 ± 0.5 
(N = 10) mm with a maximum length of 16.4 mm. 
Tissue weight increased most rapidly during Oc- 
tober. Part of the increase was due to protein and 
carbohydrate synthesis. Most of the increase was 
due to unmeasured variables: lipid deposition, 
associated with gonad development, and/or an in- 
organic component. 

Although the animals vary in weight during 
the year, the shell and water component indices 
are relatively uniform. There is a significant (P < 
0.05) decrease in shell CI in August; however, the 
meaning is obscure. It is possible that there is 
allometric shell deposition in S. transversum as 
noted in other bivalves (Joy and McCoy, 1975). 
Total protein and carbohydrate CI show a pos- 
itive correlation with reproductive activity dur- 
ing the fall and winter. Carbohydrate and protein 
CI also show a decline towards the end of the 
reproductive season. The decrease in protein and 
carbohydrate content may reflect the deteriorated 
condition of the adults which can be more readily 
observed only when large numbers of juveniles 
have been released. Protein and carbohydrate 
were not expressed as a function of dry tissue 
weight in Table 2 because a significant and 
seasonally varible amount of "adult tissue" was 
actually developing juvenile tissue and shell. The 
juveniles could not be separated from the adult 
tissue without loss of adult tissue. The quantity 
of tissue carbohydrate (6-23% of dry tissue) is 

UUTlie Nautilus 

October 27, 1977 

Vol. 91 (4) 

similar to those reported for other molluscs 
(Calvin, 1931; Webber, 1970; DeZwann and Zan- 
dee. 1972; Badman and Chin, 1973; Dietz, 1974). 
Protein content in the dry tissue ranged from 16 
to 37"o. The protein to carbohydrate ratio of 
about 2 also is similar to other bivalves (Ansell et 
al.. 19M; Ansell and Trevallion, 1967; Dietz, un- 
published observation). 


We wish to thank Mrs. Gerry Bullock for typ- 
ing the manuscript. 


Ansell. A. D., F. A. Loosmore and K. F. Lander. 1964. Studies 
on the hard-shell clam. Venus mercenana, in British 
waters. II. Seasonal cycle in condition and biochemical com- 
position../. Applied Ecot. 1: 83-9.5. 

Ansell, A. D. and A. Trevallion. 1967. Studies on Tellina 
tenuis Da Costa. I Seasonal growth and biochemical cycle. J. 
Erp. Mar. Rid F/-i>i I: i^i^-'ZW 

Badman, D. G. and S. L. Chin. 1973. Metabolic responses of 
the fresh-water bivalve, Pleurobema cnccineum (Conrad), to 
anaerobic conditions. Comp. Biuchem. Physiol. 44B: 27-32. 

Calvin. D. B. 1931. Glycogen content of fresh-water mussels. 
Proc. SrK. Erp Biol. Med. 29: 96-97. 

Dietz, T. H. 1974. Body fluid composition and aerial oxygen 
consumption in the freshwater mussel, Liqumia s^ibrostrata 
(Say): Effects of dehydration and anoxic stress. Biol. Bull_ 
147: .560-572. 

Foster. T. D. 1932. Observations on the life history of a finger- 
nail shell of the genus •Sp/i.fK'nMm. J. Morphol. 53: 473-497. 

Gale, W. F. 1976. Vertical distribution and burrowing 
behavior of the fingernail clam, Sphaerium transversum. 
Malacologia 15: 401-409. 

Gilmore, R. .1. 1917. Notes on reproduction and growth in cer- 
tain viviparous mussels of the family sphaeriidae. The 
.Vnwn/iw 31: 16-30. 

Heard, W. H. 1964. Litter size in the Sphaeriidae. The 

Heard, W. H. 1965. Comparative life histories of North 
.American pill clams (Sphaeriidae: Pisidium). Malacologia 2: 

Horst, T. .]. and Costa, R. R. 1975. Seasonal migration and 
density patterns of the fresh water snail. Amnicola limosa. 
77icAnM(i7)is 89: 56-59. 

.I(iy. .]. E. and L, E. McCoy. 1975. Comparisons of shell dimen- 
sions and vi.scera mass weights in Corbinda manilenMs 
(Philippi. 1844). The Nautilus 89: 51-.54. 

l/)wry, 0. H., N. J. Rosebrough, A. L. Farr, and R. .J. Randall. 
1951. Protein measurement with the folin phenol reagent. J. 
Biol. Chem. 193: 265-275. 

Mackie. G. L, S. U. Qadri and A. H. Clarke. 1976. In- 
traspecific variations in growth, birth periods, and longevi- 
ty of Musndium securis (Bivalvia: Sphaeriidae) near Ot- 
tawa. Canada. Malacologia 15: 433-446. 

Montgomery. R. 1957. Determination of glycogen. Arch. 
Biochem. Biophys. 67: 378-386. 

Stickle, W. B. 1975. The reproductive physiologj- of the inter- 
tidal prosobranch Thais lamellosa (Gmelin). II. Seasonal 
changes in biochemical composition. Biol. Bidl. 148: 448-460. 

Thomas. G. .J. 1959. Self-fertilization and production of young 
in a sphaeriid clam. The Nautilus 72: 131-140. 

Van Cleave, H. J., A. G. Wright and C. W. Nixon. 1947. 
Preliminary observations on reproduction in the molluscan 
^envis Muscidium. The Nautilus 6\: 6-11. 

Webber, H. H. 1970. Changes in metabolite composition dur- 
ing the reproductive cycle of the abalone Haliotis 
cracheroidii (Gastropoda: Prosobranchiata). Physiol. Zool. 

De Zwaan, A. and D. I. Zandee. 1972. Body distribution and 
seasonal changes in the glycogen content of the common sea 
mussel Mytilits edulis. Comp. Biochem. Physiol. 43A: 53-58. 


Raymond W. Neck 

Pesquezo Museum of Natural History 

6803 Esther 

Austin, Te.\as7S752 

Currently a survey of the land snails of Travis 
County, Texas, has turned up ten non-native land 
snails. Only one of these, Rumina decollata, has 
been previously reported in this county. Report of 

the other nine species has only been in a simple 
preliminary checklist (Neck, 1976b). Previous 
records exist for all these species in other parts of 
Texas (see Dundee, 1974). 

Vol. 91 (4) 

October 27, 1977 

The Nautilus 141 


Helve aspersa Miiller. Native of western and 
southern Europe. This species has been found in 
several home gardens in the Austin residential 
areas. This species is known as the European 
Brown Snail or European Spotted Snail. Occur- 
rence is spotty; populations are characteristically 
of low density and restricted to urban areas. H. 
aspersa is widespread in California but invasion 
of natural areas is quite restricted due to the an- 
nual summer drought (Potts, 1975). Frequently 
hot, dry summer months in central Texas are a 
severe obstacle to the establishment of thriving 
fwpulations of this species in other than artifical 
garden habitats. 

Otala lactea (Miiller). Native of southern Spain 
and northern Africa. Individuals of this species 
are known from home gardens as well as self- 
sustaining feral colony which contained both 
banded and unhanded snails. Banded snails have 
very dark brown, distinctive bands. Individuals of 
this feral colony were commonly seen estivating 
on the trunks of mesquite, in the same manner as 
Rabdotm altematus Say (as illustrated by 
Pilsbry, 1946:2(1): p. 5, fig. 2). Individual snails in 
gardens are relatively common but probably 
represent short-lived occurrences. Self-sustaining 
colonies may exist in small (one-fourth acre) plots 
in urban areas. This species is known as the Milk 
Snail or Spanish Snail (Dundee, 1970). 

Otala vermiculata (Miiller). Native of the 
Mediterranean area. In Travis County this spe- 
cies is knovm only from a single urban residen- 
tial locality. Feral colonies undoubtedly could 
survive as one such colony is knovra in Bastrop, 
Bastrop County, Texas, approximately thirty 
miles south-southeast of Austin. All shells seen 
have been banded; bands vary in their distinct- 
ness from light background color. 


Lehmannia poirieri (Mabille). Native of 
western and southern Europe. Extremely dense 
populations of this slug occur in ubran garden 
areas which receive supplemental watering. With 
one exception, it is unknown in rural areas. This 
population occurs on a seepage slope in the flood- 

plain of Onion Creek. Urban natural areas ap- 
pear able to support only smaller population 

Limaa- flavxis Linnaeus. Native of temperate 
Europe. This slug is much less commonly encoun- 
tered than the preceding species. Although Pils- 
bry (1948: 529) described this species as a "slug of 
cultivated places," most Austin localities of L. 
flavus are semi-natural islands in urban areas. In 
fact, L. flavus is more likely to be found in semi- 
natural urban islands than L. poirieri although 
this latter species is much more common on an 
overall scale. 

Milax gagates (Drapamaud). Native of western 
Europe including Britain and Ireland. This slug 
is rarely encountered and has been found only 
along the banks of watercourses and urban gar- 
den situations. Only a single collection (and that 
one an urban garden) is knovm since before the 
short but severe drought of 1970-71. Feral pop- 
ulations of this species should be considered 
perilous although areas of previous collection do 
not receive supplemental water. Even in the 
moist Pacific Northwest of North America, e.g. 
British Columbia, M. gagates is generally 
associated with greenhouses (see references in 
Rollo and Wellington, 1975). 


Polygyra septemvolva volvoxis Pfeiffer. Native 
to southeastern and coastal Texas and other 
coastal plains areas outside the state. In Travis 
County, this species has not been found under 
natural conditions; two localities are known— a 
greenhouse and a residential backyard which con- 
tained potted plants from this greenhouse. The 
nearest natural occurrence reported is Burleson 
County (Pilsbry 1940: 1(2):591. The Travis County 
population originated from Cameron County. This 
species is most common in warm, humid coastal 
areas. No successful reproduction was observed in 
the residential locale. Travis County may be too 
cold and/or dry for this species to survive under 
natural conditions. 


Rumina decollata Linnaeus. Native of southern 
Europe and northern Africa. TTiis is by far the 

142 'Ilie Nautilus 

October 27, 1977 

Vol. 91 (4) 

most abundant non-native snail in Travis County 
as well as much of the southern United States 
(Dundee, 1970). This species is probably the most 
familiar snail for most of the general public, be- 
cause it is the most abundant urban snail in 
Austin. R. decollata, however, is also able to col- 
onize rural areas via downstream transport. It is 
the only non-native snail species commonly found 
in rural areas. 

The first literature report of this species in 
Travis County was by Strecker (1935:23). Suhm 
(1957) reported that this species had burrowed in- 
to sediment at the Smith Rockshelter, a famous 
archeological site in southeastern Travis County. 
Branson (1959) later reported it from Zilker 
Park, an Austin municipal park. It has also been 
reported from Austin Caverns (cave now used as 
a storm sewer) and the Barton Springs archeo- 
logical site (in Zilker Park) by Reddell (1965). 

Approximate time of introduction of R. decol- 
lata in this area can be determined. The publi- 
cation by Strecker (1935) appeared posthumously 
following Strecker's death in January 1933; 
therefore, initial Travis County collections were 
made no later than 1932. The time of initial in- 
troduction into Travis County is unknown, but it 
is probably no earlier than the late 1880's as 
Singley (1893) did not record this species from 
the state. Introduction probably came later, as 
Pilsbry (1905) reviewed the world range of this 
snail but did not list any collections from Texas. 
The first Texas report of this species was by 
Camp (in Ferriss 1914) from Brovmsville. No 
other Texas localities were mentioned although 
Ferriss compared the Brownsville specimens to 
those in his collection from Louisiana and South 
Carolina. At this point, arrival in Travis County 
would most likely have been between 1915 and 

Archeological investigations of historic sites of 
the last and early twentieth centuries are poten- 
tially important sources to pinpoint when R. 
decollata became established in various areas. 
However, there is an inherent problem. Even if 
the layer from which the deep)est shells are found 
could be dated accurately, the burrowing habit of 
this snail would complicate the situation. In 
Travis County alone, this species has been found 
in several archeological excavations of pre- 

European sites (see references in first paragraph). 
Estimates of time of arrival of this snail would 
most likely be on the early side. 

Oppas pyrgula Schmacker & Boettger. Native 
of Japan and China. This small snail has been 
found living in two residential localities. Some 
individual dead shells have been found in urban 
natural areas which are downstream from resi- 
dential areas. These shells indicate further urban 
colonies. No feral colonies have been established 
by such downstream dispersal of living snails, 
however. Colonies observed occur in areas pro- 
tected from cold winter winds and dry, hot sum- 
mer weather conditions. 

Cedlioides Ojcicula (Muller). Native of central 
and western Europe. This minute species is 
known from the banks of a creek running 
through a residential area. Only a single living 
specimen was found, but this blind species is 
generally subterranean in habit (Pilsbry, 1909) 
which would reduce collecting chances. This 
species has been reported feeding on grass roots 
to a depth of 40 cm while preferring "soils rich in 
lime" (Likharev and Rammal'meier, 1952). Report 
of this snail in Travis County at this locality has 
been previously mentioned (Neck 1976a). No sub- 
sequent collections have been made, even at the 
original collection site. 


Introduced snails may occur in rural, urban 
natural or residential areas. A species occurring 
in a residential area may be totally dependent 
upon human activites for maintenance of a viable 
population. Occurrence in urban natural islands 
indicates an ability of the species to survive 
under natural conditions. Occurrence in rural 
natural areas would indicate an ability to col- 
onize new habitats on their own. 

Significantly, the most successful non-native 
snail of Travis County, Texas, R. decollata, is 
from the Mediterranean area. Central Texas does 
not have a Mediterranean-type climate, but the 
summers are often very dry. R. decollata is well- 
adapted to survive arid periods. The ability to 
produce offspring parthenogenetically (Selander, 
et al., 1974) is also very important in its ability 
to rapidly populate newly colonized areas. 

Vol. 91 (4) 

October 27, 1977 

The Nautilus 143 

Non-native snails are introduced by a variety 
of means, either accidentally on ornamental 
plants or deliberately as fish bait. Almost all of 
the introduction to Travis County were probably 
accidental. The feral colony of Otala lactea could 
have been a deliberate introduction. 


Branson. B. A. 19.59. Riinmm decollata in Oklahoma. The 

Naulihis 73: 37. 
Dundee. D. S. 1970. Introduced Gulf Coast molluscs. Tidane 

Studies Z00I.& Bat. 16: 101-115. 
Dundee. D. S. 1974. Catalog of introduced molluscs of eastern 

North America (North of Mexico). Sterkiana 55: 1-37. 
Ferris, J. H. 1914. Rumina decollata in Texas. The Nautilus 

Likharev, I. M. and E. S. Rammel'meier. 1952. Terrestrial 

mollusks of the fauna of the U.S.S.R. Trans Y. Lengy and Z. 

Kraut hamer. 1962. Isreal Prog. Sci Tran., Jenisaiem. 
Neck, R. W. 197()a. Cecilundes acicula (Miiller): Living colon 

ies established in Texas. Sterbmia 61: 19-20. 
Neck, R. W. 1976b. Preliminary checklist of land snails of 

Travis County. In A bird finding and naturalist's guide for 

the Austin. Texas, area. E. A. Kutac and S. C. Caran. pp. 
124-129. Oasis Press, Austin. Texas. 

Pilsbry, H. A. 1905. Rumina decollata L. Manual of Con- 
chologyn: 212. 

Pilsbry, H. A. 1909. Caecilimles. Glessula and Partulidae. 
MaunalofCom-hol<igy20: 1-336. 

Pilsbry, H. A. 1939-1948. Land moUusca of North America 
(North of Mexico). Acad. Nat. Sci. Phil.. Monog. 3. 2 vol. 

Potts, D. C. 1975. Persistence and extinction of local popula- 
tions of the garden snail Helijc aspersa in unfavorable en- 
vironments. Oecologia 21: 313-334. 

Reddell. J. R. 1965. A checklist of the cave fauna of Texas. L 
The invertbrata (exclusive of Insecta). Texas Jour. Sci. 17: 

Rollo, C. D. and W. G. Wellington. 197.5. Terrestrail slugs in 
the vicinity of Vancouver. British Columbia. The Nautihis 
89: 107-115. 

Selander, R. W., D. W. Kaufman and R. S. Ralin. 1974. Self- 
fertilization in the terrestrial snail Rumina decollata. 
Veliger 16: 165-170. 

Singley, J. A. 1893. Texas mollusca. Fourth Ann. Rept. Geol. 
Siirv. Texas : 299-343. 

Strecker. J. K. 1935. Land and fresh-water snails of Texas. 
Trans. Texas Acad. Sci. 17: 4-44. 

Suhm, D. A. 1957. Ejicavations at the Smith Rochshelter. 
Travis County, Texas. Texas Jour. Sci. 9: 26-58. 


A. Byron Leonard 

Department of Systematics and Ecology 

University of Kansas 

Lawrence, Kansas 66045 

In the course of geological and paleontological 
studies of late Cenozoic deposits in northeastern 
New Mexico, with a colleague. Dr. John C. Frye, 
and under the auspices of the New Mexico Bu- 
reau of Mines and Mineral Resources, a mollus- 
can fauna comprising some 27 species was 
discovered in the Kimball seed zone (Ogallala 
Formation, late Pliocene) sediments. Molluscan 
fossils in the Ogallala Formation are rare, and 
well-preserved shells even more so. The shells oc- 
cur in caliche-cemented, fine sand, however, and 
shells suffered some damaged in the recovery pro- 
cess. Among the shells discovered in the deposit 

are three kinds judged to undescribed taxa. Their 
descriptions follow. 

Tiffie Locality: Late Pliocene deposits exposed 
in a small draw, tributary to Sand Draw, about 
100 yards east of N. M. State Highway No. 18, 
and about 8 miles south of the junction of N. M. 
18 and U. S. Highway 65 in Clayton, Union Coun- 
ty, New Mexico, and situated in the SW '4 SE '4 
sec. 2, Twp. 24 N, R 35 E, Union County, N. M., 
Lat. 36° 20' 14" N., Long. 103°, 09' 31" W. in an 
exposure known as the Clayton South Section. 
The types are deposited in the New Mexico 
Bureau of Mines and Mineral Resources, Socomo, 

144 The Nautilus 

October 27, 1977 

Vol. 91 (4) 

FIGS. 1-3. Hi)liit ifiicx. Fig. 1, Lymnaea cla>tonensis, /(. sp.. x 
5. Fig. 2. Gastrooipta debilis, n. sp.. i 10. Fig. S, Gastrocopta 
arena, «. sp.. x 10. Magnifications approximate. 

Lymnaea claytonensis, n. s-p. 
Fig. 1 

Dinqnoiii.'i: A slender l>Tnnaeid shell, having 5 
to 6 rounded whorls, shouldered above, and hav- 
ing a laterally compressed, elliptical aperture, oc- 
cupying about one-half the total length of the 

Description of holoti/pe: Shell of slender lym- 
naeid form; whorls a little more than 5 in num- 
ber, rounded and somewhat shouldered; suture 
well-impressed, slanting obliquely forward; aper- 
ture elliptical, outer peristome simple and thin, 
parietal wall adnate upon body whorl, and twist- 
ed upon the umbilicus reducing that opening to a 
narrow chink; nuclear V2 whorls having granu- 
lar surface, remaining whorls with distinct, 
slightly oblique, vertical ridges, crossed by fine 
spiral lines, producing a satinlike surface tex- 
ture; total length, 7.0 mm, diameter, 2.80 mm, a- 
perture length, 3.64 mm, aperture width, 2.10 mm. 

The specific name, claytonensis. derives from 
the name of the section, in turn derived from the 
nearby town of Clayton, Union County. New 
Me.xico, Holotype in NM 52-75-1; paratypes in 
NM 52-75-12. 

Comparisons: Some paratypes are larger than 
the type (but damaged), reaching an estimated 
length of nearly 11 mm. The ultimate whorl on 
these older shells is often characterized by revolv- 
ing ridges, about 5 in number; or the last whorl 
may be irregularly malleated. None of these 
features is judged to have taxonomic significance. 
Lymnaea claytonensis, although differing from 

them in its more slender shape, and compressed, 
elliptical aperture, seems to relate best to the 
Lymnaea kumilis-truncatula-cubensis complex, 
because of the general proportions and size of the 
shell, and the fine spiral sculpture. Its closeness 
to the circumcaribbean cubensis may indicate a 
southern element in the lymnaeid fauna at this 

Gastrocopta debilis, n. sp. 

Fig. 2 

Diagnosis: Shell small, bearing the characters 
of the genus, about 2.5 mm in length; whorls five, 
rounded; aperture irregularly rounded, peristome 
reflected, lip thin, having well-developed crest 
behind, separated from the lip by a well-devel- 
oped trough; denticles 4, the two palatals weakly 
developed to almost absent. 

Description of holotype: Shell minute, subcylin- 
dric, tapering slightly toward blunt apex; whorls 
five, rounded, bearing surface sculpture of fine, 
irregularly disposed diagonal striations, except 
for finely granular apical I'z whorls; suture im- 
pressed; aperture about as high as wide, peris- 
tome reflected, thin, but bearing a callus within; 
margins of peristome approaching, but connected 
by no more than a thin wash across parietal 
wall; a strong crest parallels outer peristome 
separated from it by a trough; no impressions 
behind palatal folds; denticles 4: angulo-parietal 
simple in all views, inclined slightly toward the 
right; columella lamella simple horizontal, nei- 
ther entering nor ascending; two palatal folds, 
lx)th weakly developed, the lower more elongate 
and more deeply entering than the upper; basal 
fold absent. 

The name debilis refers to the weakly 
developed palatal folds. Holotype deposited in 
NM 52-76-1; paratypes in NM 52-76-5. 

Compansons: There is a minimum of variation 
among the numerous paratypes. but what occurs 
is related to the strength of the two palatal folds. 
Among a hundred shells, four of them have 
palatal folds more than weakly developed, and in 
another four of them, the two palatal folds are 
essentially absent. G. debilis superficially 
resembles G. pellucida parvidens of Sterki but 
differs from that species in the simple angulo- 
parietal fold, and the prominent crest behind the 

Vol. 91 (4) 

October 27, 1977 

The Nautilus 145 

peristome. G. debilis differs from G. cortu-aria in 
that the latter lacks the crest behind the 
peristome, the angulo-parietal is not simple, and 
the two palatals in corticaria are strongly 

Gastrocopta arean. ii. xp. 
Fig. 3 

Diagnosis: A small ovoid gastrocoptid, little 
more than 2.0 mm in length, having five rounded 
whorls, flared aperture with crest behind the 
peristome, and four denticles: angulo-parietal, 
columellar and 2 palatals. 

Description of holotyve: Shell elongate, ovoid, 
imperforate; 5 convex whorls, smooth nuclear 
whorl forming bluntly conic apex the granular 
surface texture extending to last half of ultimate 
whorl but beyond first IV2 nuclear whorls, over- 
lain by fine diagonal striations, aperture having 
flared, simple peristome, with crest behind, the 
right margin extending toward, but not reaching 
opposite margin, to which it is connected only by 
thin callus; denticles 4: angular limb of angulo- 
parietal extending from parietal limb and joining 
with margin of peristome, parietal limb elevated, 
elongate, extending deeply within aperture; col- 
umellar lamella nearly vertical; basal lamella ab- 
sent; upper palatal lamella conic and rising from 
a thick callus, the tip closely approaching pa- 
rietal lamella; lower palatal nodular, very deeply 
inserted in aperture and smaller than upper pa- 
latal lamella; the palatal lamellae producing an 
elongate impression behind the peristome. Total 
length, 2.38 mm; diameter, 1.2 mm, aperture 
length, 0.77 mm, aperture width, 0.84 mm. Gas- 
trocopta arena is known only from the holotype 
(NM 52-76-21) and three paratypes (NM 52-76-5) 
the shells of the paratypes are variously 

Tlie name arena refers to the fine sandy 
matrix from which this and other taxa of mol- 
lusca were recovered. 

Comparisons: Similar in form and in the 
general configuration of the denticles to G. ar- 
mifera, from which it differs by its small size, 
about half that of annifera, by the simple, un- 
twisted columella lamella, and by the deeply im- 
mersed, nodular lower palatal lamella. The sur- 
face texture is also unique, as the granular al- 
most waxy surface sculpture extends to the last 
half of the ultimate whorl, where diagonal stria- 
tions suddenly begin. G. arena bears no 
resemblance to any of the small gastrocoptids 
known to me. 

The three taxa of gastropods described above 
are known only from the type locality, given 

The total molluscan fauna recovered from the 
Clayton South locality includes 25 taxa, listed as 
follows in generic alphabetical order: 


Fcirissiaparallela (Haldemian) 
Ferrissia shimeki (Pilsbry) 
Ferrissia tarda. (Say) 

Gyraulus cxrcumstriatus 

G. parviLS F. C. Baker 
Lynmaea bulimoides Lea 
L. claytonensis. n. sp. 
L. ddli F. C. Baker 

L. parva F. C. Baker 
Physa anatirui Lea 
Pisidium casertanum (Poll) 


Evjconuiusfidms (Muller) 
Gastrocopta arena n. sp. 
G. cristata (Pilsbry 
& Vanatta) 

G. debilis. n.sp. 

G. pUsbryana (Sterki) 

Hawaiia mimiscida (Binney) 

Pupilla blandi Morse 

Pupoides albilabris 
(C. B. Adams) 

P. hordaceus (Gabb) 

P. inomatus Vanatta 

P. modicus (Gould) 

Suiccinea grosvenori Lea 

Sucdneagelida F. C. Baker 
Valloniaperspectiva Sterki 
Vertigo milum (Gould) 

146 The Nautilus 

October 27. 1977 

Vol. 91 (J) 


Alan Solem 

Department of Z<)ol()g>' 

Field Museum of Natural History 

Chicago. Illinois 60605 


A pamtifpp of Radiodiscus hubrichti Brnnsori. 1975. compares exactly inth 
material of Striatura (S.) pugetensis (Dall, 1895). The tiro taxa are considered 
to be Hynonyms. Scanning electron microscope photographs of shell sculpture in 
the two distinct species. S. (S.) pugetensis and S. (S.) milium (Morse. 1S59J. 
show that they have basically identical sculpture. 

The minute (1-3 mm) shells of such genera as 
Striatura, Punctum. Radiodvictis. and Planogyra 
are easily confused. They have a common pattern 
of decoiling and spire protrusion, all have radial 
ribbing interspaced with microribs, and in each 
group the apical and post-apical sculpture are 
markedly different. Even the best illustrations 
published previously (Pilsbry, 1946, 1948) suggest 
that there are more similarities than differences. 
Use of the scanning electron microscope permits 
showing that the shell sculpture in these genera, 
although very similar in gross appearance, is 
formed quite differently. TTiis paper reports on 
the basic sculpture of Striatura, s. s., while a 
subsequent contribution (Solem, in this issue of 
The Nautilus) will illustrate the same features as 
found in Striatura (Pseudohyalina). Punctum, 
Radiodiscus and Planogi/ra. Comparative remarks 
are included in the second paper. 


Although much of the surface in the paratype 
of Radindiscus hubrichti (FMNH 175456) is 
coated with debris (figs. 4, 5). sufficient clean 
areas remain so that details of the 
microsculpture could be studied (figs. 6, 7). The 
apical sculpture for the first l-3/8ths whorl con- 
sists of crowded spiral ridges (fig. 5). There is an 
intrusion of weak radials on the remaining 
slightly more than one-eight apical whorl. A con- 
striction at the suture marks the end of this 
region. The post-nuclear sculpture consists of pro- 
minent radial ribs and weak .'spiral elements. Tliis 

continues to the lip edge. Viewed at intermediate 
magnification (fig. 6), the radials are seen to be 
narrow thread-like elevations on top of weakly 
raised ridges. At high magnification (fig. 7), the 
inter-rib area shows "pits and swirls". There are 
distinctive mirco-folds on the pit edges as well as 
the surface of the radial ribs (upper left). 

The apical sculpture of Striatura milium (fig. 
1) is the same as that found in S. pugetensis. Ti\e 
post-nuclear sculpture (figs. 2, 3) of S. milium ap- 
pears different at first glance, since the raised 
radial threads of 5. pugetensis (fig. 6) are absent. 
When viewed at comparable high magnification 
(fig. 3), the "pits and swirls" found in inter-rib 
areas of 5. piigetensis (fig. 7) are seen to be inten- 
sified in S. milium and represent the only post- 
nuclear sculptural element. 

At the highest magnification (figs. 3, 7), both 
species show a very peculiar pattern of micro- 
folding. This folding is very similar to stress 
marks seen in dried paint or plastic films. It is 
interpreted as the result of periostracal shrinkage 
drying. This "folding" also is characteristic of 
many zonitoid (Solem. unpublished) and pupillid 
taxa (see also Gittenberger. 1975. pi. I, fig. 4 and 
Solem. in this issue of The Nautilus. 


Striatura (S) pugeten.vs (Dall, 1895) has a 
sporadic distribution from Vancouver Island 
south to Guadeloupe Island. Baja California, and 
the Palomar Mountains near San Diego (Pilsbry, 
1946: 492). It is quite common near Seattle and 


October 27, 1977 

The Nautilus 147 

FIGS. 1-3. Striatura (S.) milium (Morse, mn)- FMNH mnHH. 
Near Minden. Halliburton Co.. Ontario. Canada. P. M. 
Oughton! FIG. 1. Nuclear sculpture. 560X. FIG. 2. S<-ulpture 
on body whorl near aperture. 56.5X. FIG. 3. Detail of two 
"ribs" m body whorl. 1.670X. FIGS. 4-7. Striatura (S.) 
pugetensis (Ml. 1895). FMNH mU56. Paratype "f 

Radiodiscus hubrichti Branson, wr.:. Ml. Storm King. Olym- 
pic Penhmda. Washington. FIG. 4. Sid^ mew of shell. S6X. 
FIG 5. Top view of shell. S6X. FIG. 6. Sculpture on body 
whorl showing the raised "ribs" on top of the same pattern 
.^een m Fig. 2. 370X. FIG. 7. Detail oftuv radial ribs shownng 
shrinkage pattern and inter-rib pits and swirls. 1.510X. 

148 The Nautilus 

October 27, 1977 

Vol. 91 (4) 

on the Olympic Peninsula, from which Radw- 
discus hubrichti was described. TTie dimensions 
cited by Branson (1975), his description, and his 
figures, all agree with the information concerning 
S pugetevsis given by Pilsbry (1946). Direct com- 
parison of a paratype of I\ii<li(iili.snii< hubrichti 
(FMNH 175456) with the more than 25 sets of S. 
pugetensis in the collection of Field Museum of 
Natural History leaves no doubt that the two 
taxa are identical. 

The following localities for S. pugetensis have 
not been published previously. They somewhat 
extend the distributional limits cited by Pilsbry 
(1946: 492), and are grouped by state for conven- 
ient reference. 

Wcufhington: Kittitas Co., 10 miles west of 
Easton (FMNH 63076. H. S. Dybas! June 20, 1957; 
Jefferson Co., Olympic Hot Springs (FMNH 
63074, H. S. Dybas! June 19, 1957). 

Idaho: Kootenai Co., Medimont (FMNH 63075, 
FMNH 63078, H. S. Dybas! June 23, 1957). 

Montana: Flathead Co., T32N, R18W, SB 
Glacier Park (FMNH 110716, Marie Mooar! July 
7, 1960). 

Oregon: Curry Co., ravine of Pistol River 
(FMNH 117741, H. S. Dybas! May 23, 1957); Hood 
River Co., Cascade Locks (FMNH 54322, H. W. 
Harry! November 1945). 

California: San Francisco, Marina Hospital 
(FMNH 97655, W. H. Dall! ex Fred Button); 
Alameda Co.. Hayward (FMNH 97708. ex Fred 
Button); Sacramento Co.. northeast of Folsom 
(FMNH 97956, A. Solem & A. Smith! April 9, 

1960); San Diego Co.. San Diego (FMNH 63077. ex 
Walter F. Webb). 


The scanning electron microscope photographs 
were made during a factory demonstration by 
JEOLCO (figs. 1-3) and with a Cambridge 
Stereoscan provided Field Museum of Natural 
History through National Science Foundation 
Grant BMS72-02149 AOl, A. Solem, Principal In- 
vestigator. I am grateful to both organizations for 
their support. Mr. Fred Huysmans, SEM Techni- 
cian at Field Museum, is responsible for the high 
quality of the photographic prints, which were 
mounted by Dorothy Karall. Dr. Branley A. 
Branson kindly deposited a paratype of his new 
species with the Field Museum of Natural 


Branson, B. A. 1975. Radioriixnix hiibrifhti (Pulmonata; En- 

dodontidae) new species from the Olympic Peninsula, 

Washington. The Nautilus 89: 47-48. 
Gittenberger, E. 197.5 Beitrage zur Kenntnis der Pupillacea 

VI. Die Gattung Agardhielta in Jugoslawien. Zml. Meded... 

Uiden 48(24): 279-289, pi. 1, 6 text figs. 
Pilsbry, H. A. 1946. Land Mollusca of North America (North 

of Mexico). Acad. Nat. Sri.. Philadelphia, Monog. 3, 2(1): 

i-vi,l-.520, figs. 1-281. 
Pilsbry, H. A. 1948. Land Mollusca of North America (North 

of Mexico). Acad. Nat. Sci.. Philadelphia, Monog. 3, 2(2): i- 

xlvii, 521-1 11,3. figs. 282-585. 
Solem. A. 1977. Shell microsculpture in Striatura, Punctum, 

Radiodiscus. and Planogyra, The Nautilus 91(4) in this 



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Vol. 91 (4) 

October 27, 1977 

The Nautilus 149 


Alan Solem 

Department of Zoology 

Field Museum of Natural History 

Chicago, Illinois 60605 


Previous anatomical studies have placed Striatura (Zonitidae), Punctum 
fPunctidae). Radiodiscus (Charopidae), and Planogyra (Valloniidae) in unrelated 
families. Their minute size, similar shell shapes, and the sharj) differentiation 
between spiral sculpture on the nuclear whorls and the post-nuclear scidpture 
of major and minor radial elements, have led to confusion between these 
genera. Scanning electron microscope photographs of shell microsculpture show 
that the apparent sadptural similarities are ctmvergent. The same gross residt 
is achieved in guite different ways. 

In many parts of the world, land snails that 
are 1 to 2 mm in diameter have a complex micro- 
sculpture on the shell. When this sculpture is 
viewed under high optical magnifications, 50 to 
lOOX, a distinction can be made between "major 
radial ribs" that number 15 to 250 on the last 
whorl of the shell, and "micro-ribbing" that lies 
between the "major ribs". Traditionally such 
species were described as, or subsequently 
associated with, "endodontid" land snails but 
anatomical investigations of the past six decades 
have split many taxa off into a wide variety of 
families. The many differences in pallial struc- 
ture, genitalia, radulae, free muscle and nervous 
systems revealed by the anatomical studies 
strongly suggest that the similarities in shell 
form and sculpture are the result of convergent 

Unfortunately, adequate studies of the sculp- 
tural elements and their method of formation 
have not been possible until very recently be- 
cause of inherent limitations in magnifications, 
resolution, and depth of field with optical equip- 
ment. TTie scanning electron microscope (here- 
after SEM) overcomes these problems and per- 
mits investigations of sculpture components and 
method of formation. As a byproduct of investiga- 
tions on the Pacific Basin endodontoid land 
snails, data on shell sculpture in several Nearctic 
taxa have been accumulated. They illustrate basic 

differences in mode of sculpture formation and 
suggest possible major differences between higher 
groupings in terms of shell structure. 

The genera illustrated here, and the anatomical 
studies that enabled definitely assigning them to 
family units, are Striatura (Pseudohyalina) 
(Zonitidae, H. B. Ba}{er, 1928a), Punctum (Punc- 
tidae, H. B. Baker, 1927), Radiodiscus 
(Charopidae, H. B. Baker, 1927), and Planogyra 
(Valloniidae, H. B. Baker, 1928b. 1935). Illustra- 
tions of two species belonging to Striatura s. s. 
were presented in the preceding paf)er, Solem 
(1977) and are referred to below. The Valloniidae 
belongs to the Order Orthurethra and the other 
three families to the Order Sigmuretha. Both the 
Punctidae and the Charopidae currently (Solem, 
In Press) are placed in the Superfamily Ariona- 
cea of the Suborder Aulacopoda, while the Zon- 
itidae belongs to the Superfamily Limacacea of 
the same Suborder. None of these families appear 
to be related in a direct descendant-ancestor 

The families also differ greatly in their basic 
distribution patterns. The Charopidae (Solem, un- 
published) is a "Gondwanaland" taxon with high 
diversity in South Africa, Australia, New Zea- 
land, New Caledonia, some parts of Polynesia, 
Juan Fernandez and southern South America. A 
few taxa reach Indonesia, New Guinea, Central 
America, and the Western United States. The 

150 The Nautilus 

October 27, 1977 

Vol.91 (4) 

Punctidae are primarily Australia and New Zea- 
land in distribution, with scattered occurrences 
in Afrira, Sduth America. Tahiti. Hawaii, and the 
Holarctic region. The Zonitidae is most diverse in 
the Holarctic, but has extensive Central Amer- 
ican, Polynesian, and some South American taxa. 
The Valloniidae is strictly a Holarctic family 
with a fossil record extending back to the Pale- 
ocene of Europe. North America is thus on the 
fringe of the charopid radiation, but central to 
the zonitid and valloniid distribution patterns. 
The punctids have their center of diversity 
elsewhere, but North America is the main secon- 
dary center of diversity. 


Although Baker (1928a: 33) pointed out that 
the three dissected species he grouped as 
Striatura could perhaps be placed better as 
monotypic genera, subsequent workers such as 
Pilsbry (1946) preferred to use a more broadly 
defined genus. Certainly the shell sculpture in S. 
pugetensis (Ball, 1895) (see Solem, 1977: figs. 1-3), 
S. milium (Morse, 1859) (see Solem, 1977: figs. 
4-7), and S. (Pseridohyalirmj erigiia (Stimpson, 
1850) (figs. 1-3) is consistent with a monophyletic 
derivation. The species differ obviously in their 
major ribbing. 5. exigua has widely spaced, nar- 
row, high major ribs (figs. 2, 3) that terminate 
short of the suture (fig. 1). S. pugetensis (Solem, 
1977: figs. 5, 6) has much lower, more crowded, 
narrow ribs. Tliese ribs clearly are periostracal in 
origin, since (loc. cit.. left center of fig. 6) broken 
rib edges show no underlying calcareous support. 
S. milium (Solem, 1977: figs. 2, 3) gives the ap- 
pearance of having radial ribs under optical ex- 
amination, but the SEM shows that a series of 
short diagonal ridges are lined up in a radially 
transverse row and hence there are no continuous 
radial ribs. ■S'. erifiiid (figs. 2, 3) has a clear micro- 
spiral sculptural element that could be derived 
from the diagonal ridges of S millium (Solem, 
1977: fig. 2). 

The apical sculpture of S miliiim (Solem, 1977: 
fig. 1) consists of broad, flat ridges separated by 
narrower grooves, with faint traces of a radial 
element. In both S. pugetensis (Solem, 1977: fig. 
5) and 5. exigua (fig. 1) the apex has very narrow 

spiral ridges, with their interstices wider than 
the ribs. 

TVie most characteristic feature of Striatum is 
the very peculiar micro-folding pattern (Solem, 
1977: figs. 3, 7). This is particularly clear on the 
major rib surface in S. exigtut (fig. 3). Similar 
stress marks in dried films of paint or plastic are 
familiar to physical chemists. I interpret this 
folding pattern as the result of shrinkage drying 
by an outer periostracal layer. 

Piinctum (figs. 4-6, 11, 12) superficially looks 
very similar to Striatura in sculpture, having 
spiral apicals (Giusti, 1973: pi. 5, fig. 1) and nar- 
row, crowded radial ribs when viewed at optical 
range magnification (fig. 4). At higher magnifica- 
tion (figs. 5, 6), the presence of two or three 
micro-riblets between each pair of major ribs is 
obvious. By inspecting an area where the ribs are 
broken (fig. 6), the very thin, lamellar nature of 
the ribs, the occasional sudden termination of a 
micro-riblet, and the fact that the major ribs sur- 
mount a low radial swelling on the shell surface 
can be detected. When the sculpture is viewed 
from a very low angle (figs. 11, 12), the presence 
of spiral swellings, with the radial sculpture 
essentially unaffected by these elements, is evi- 
dent. In addition, there is a vague pattern of cor- 
rugations on the surface of the spiral ridges. 

Previous reports on the shell sculpture of 
Radiodiscus (summarized by Pilsbry, 1948: 
654-655) characterize the apex as "minutely 
engraved spirally" and the "rest of the shell 
densely radially costate". While the apex does 
start out (fig. 7) with continuous spiral cords, 
very shortly these become interrupted by narrow 
radial lines. At very high magnification (fig. 8), 
the apical sculpture can be seen to consist of 
short, slightly sinuated segments that line up 
spirally. The post-nuclear sculpture (figs. 9. 10) is 
complex, and compares in all essentials with that 
found in such Pacific charopids as the New Zea- 
land Ptychodon microundidata (Suter, 1890) (see 
Solem, 1970: pi. ,59) and a still undescribed 
Tongan species (Solem, 1974: 199, figs. 8a, b). TTie 
major radial ribs in all these taxa are perios- 
tracal extensions above a calcareous swelling 
(Solem, 1974: 199. fig. 8b). There are a few to 
many micro-riblets, again formed by the perios- 
tracum, between the major ribs (fig. 9; Solem, 

Vol. 91(1) 

October 27, 1977 

The Nautilus 151 

1970: pi. 59, figs. 8, 9; Solem, 1974: 199, figs. 8a, 
b). In addition, there is a complex spiral micro- 
sculpture (fig. 10). Larger spiral elements (also 
visible in fig. 9) connect two microradials, tend- 

ing to buttress the apical side of the microradial. 
This is particularly evident in Ptychodon micro- 
undidata (Solem, 1970: pi. 59, fig. 10), but is much 
less developed in Radiodvscus (figs. 9, 10). Be- 



FIGS. 1-3. Striatura (Pseudohyalina) exigua (Stimpsim. 
1850). Ohin. FMNH 110-20. FIG. 1. Apical (left.) and poi^t- 
miclear fright) sculpture. 1S5X. FIG. Z Sculpture on body 
whorl shouing one major radial rib. 620X. FIG. 3. Mail of 
penoMmad snrfarr on major nb. l.HmX. FIGS. 4-6. Punctum 

minutissimum (Lea. mi). Cedar bog on Woodburn Road. J, 
miles southwest of Urbana. Champaign Co.. Ohm. October 20. 
1969. E. Keferl! FMNH 151102. FIG. 4. Entire shell (hp 
broke II) (iSX FIG. .5. Sculpture on bod,j whorl. 1.5t>0X. Broken 
ends of major radial (left) and two microradiak (center and 
right). 5.mX. 

152 The Nautilus 

October 27, 1977 

Vol.itl (1) 


FIGS. 7-10. Radiodiscus (R.) millecostatus Pihhry & Ferriss. 
1906. Wickerxham (iulch, Huachuca Mts.. Cochise Co.. 
Arizona. James Ferriss! FMNH U6619. FIG. 7. Apical 
sculpture. 195X. FIG. 8. Detail of late apical sculpture. 1.900X. 

FIG. 9. Tu'o major ribs on body whorl. 630X. FIG. 10. Detail of 
a major rib and mirrorihlets on body irhorl. ilKXlX. FIGS. 
11-12. Punctum minutissimum (Lea, mi). FMNH 1H1W2. 
FIG. 11. Sculpture on body whorl. 2.()i»)X. FIG. 12. TktaU of 
microsculptwre on body whorl. 6.700X. 

Vol. 91 (4) 

October 27, 1977 

The Nautilus 153 

FIGS. 13-15. Planogj-ra asteriscus (Morse. 1857). FVaserdalf, 
Cochrane Dist.. Ontario. Canada. S. D. Downing! June 1938. 
FMNH 1,6T8S. FIG. 13. Apical view of siibadidt specimen. 36X. 
FIG. 14. Major rib and microsadpture on body tvhorl. 355X. 
FIG. 15. Apical sculpture and early post'uuclear scidpture. 

.W.5.V. FIGS. 16-18. Planog>Ta clappi (Pilsbry. 1898). 
Quamicham. Vancouver Id.. British Columbia. FMNH U0588 
ex W. J. Eyerdam. FIG. 16. Apical I'iew ofsubadult specimen. 
37.3X FIG. 17. Scidpture on body whorl. 373X. FIG. 18. Broken 
edge of body whorl shouintj major rib and detaih of 
mierosculpture. 792X. 

154 The Nautilus 

October 27, 1977 

Vol.91 (4) 

tween these "major" spiral elements are vague 
sprial corrugations (fig. 10; Solem, 1970, pi. 59, 
figs. 10, 11) that resemble those found on the 
spiral ridges in Punctum (fig. 12). 

Planoyyra asterifscus (Morse, 1857) (figs. 13-15) 
from the boreal areas of Extern North America 
and P. clappi (Pilsbry, 1898) (figs. 16-18) from 
Oregon to British Columbia differ from each 
other in major rib spacing (compare figs. 13 and 
16) and umbilical width. They both have very 
high, lamellar periostracal ribs that stand erect 
when the live animal is in the moist litter, but 
warp and twist (fig. 11) in the dry museum cab- 
inets (H. B. Baker, 1928a: 122). Seen at a broken 
edge (fig. 18), the periiKstracal nature andthinness 
of the ribs is obvious. Similarly, the microradial 
riblets are formed by the f)eriostracum (fig. 17) 
and are fewer in number in P. chtpiii (fig. 17) 
than in P. asteriscus (fig. 14). Both species have 
a weak microspiral sculpture that shows most 
clearly in figs. 14 and 18 because of the oblique 
angle of view. The microspirals blend into the 
raised radial ribs, but do not buttress them as in 
many CTiaropids. The apical sculpture in Plan- 
ogyra usually is eroded, but in unworn examples 
(fig. 15) it can be seen to form a series of cor- 
rugated wrinkles and pits with a vague diagonal- 
ly radial pattern. At the highest magnification 
(fig. 18) there are evident irregularities on the 
periostracal surface. These appear homologous to 
the structures on the spiral microribs of Rndio- 
discus (fig. 10) and Punctum (fig. 12), and quite 
different from the stress drying marks in .S7n- 
atum (fig. 3; Solem, 1977: figs. 3, 7). 


Under optical examination, the spiral apical 
sculpture and post-nuclear sculpture with both 
major radials and usually microradials found in 
the four genera appear quite similar, but at the 
higher magnifications of the SEM, major dif- 
ferences appear. In both Striatura and Planogyra, 
the shell sculpture appears to be totally 
periostracal in nature. The raised major ribs are 
simple lamellar protrusions from the surface. 
They are scarcely wider at their base than at 
their midsection (figs. 2, 18). In Punctum and 
Radindwcu.% the microradial riblets are purely 
periostracal, but the major radial ribs are 

underlaid and partly formed by a swelling in the 
calcium layer. Punctum (fig. 6) differs in that the 
periostracal ribs are simple lamellae, while in the 
Charopidae (Solem, 1974: 199. fig. 8b) the basal 
portions of the periostracal ribs are distinctly 
wider than the middle sections, with tapering 
continuingto the topof the ribs. 

Microspiral sculpture is present, but differs 
greatly. In Striatum (fig. 2; Solem, 1977: figs. 2, 
3, 6, 7) the spiral elements initially are short 
diagonals, becoming coalesced into wavy spiral 
cords only in S. eodgua (fig. 2). In both Planogyra 
(fig. 18) and Punctum (figs. 11. 12) ' the 
microspirals are basically independent of the 
radial ribs and riblets, but in Radiodiscus (figs. 9, 
10) they serve to buttress the apical edge of each 
riblet. In Punctum and Radiodiscus, weak spiral 
corrugations are associated with the sprial ridges. 

All four genera have spiral sculpture on the 
nuclear whorls. In Radiodisciis (figs. 7, 8) this 
consists of short interrupted threads arranged 
serially in spiral rows, although other charopids 
(Solem, 1970: pi. 58, fig. 1) normally have promi- 
nent, narrow spiral cords, such as are seen in 
both Punctum (Giusti, 1973; pi. 5, fig. 1) and 
Striatura (fig. 1). Planogi/ra (fig. 15), in contrast, 
has a less well defined, almost punctate 

The most striking difference is the peculiar 
micro-folding pattern found in Striatura (fig. 3; 
Solem, 1977: figs. 3, 7). This effect is lacking fi-om 
the other taxa, although having analogous struc- 
tures in some other Orthurethra (see Solem, 

The sculpture of these four taxa, although 
"macroscopically" veiy similar and functionally 
probably serving an identical purpose, is com- 
posed of quite different elements. On the basis of 
this and other data available now, primarily a 
review of Pacific Basin endodontoid taxa, it 
seems possible that certain of these differences 
are consistent for at least family units. TTie total 
periostracal nature of the shell sculpture in 
Stivatura and Planogyra contrasts with the com- 
bination of calcareous and periostracal sculpture 
in Punctum and Radiodiacus. At the other ex- 
treme the Endodontidae, as restricted by Solem, 
has a uniformly thin periostracum, with even 

Vol. 91 (4) 

October 27, 1977 

The Nautilus 155 

the microsculpture on the apical whorls formed 
mainly by the calcareous layers. Except where 
the sculpture is secondarily reduced in the 
Charopidae, the combination of periostracal and 
calcareous elements is consistent, as is the use of 
microspiral ridges to buttress the riblets. In the 
valloniids, species of Vallonia with regularly 
spaced ribs do have calcareous extensions into the 
ribs, and some of the punctids from Australia 
and New Zealand lack the calcareous swellings 
underneath the main ribs. 

The tapered and buttressed ribs in the 
Cliaropidae are quite unlike the simple lamellar 
ribs of the other taxa, while the stress folds and 
"pit and swirl" microsculpture of the zonitid 
Striatura separate it from the other three. A 
study of the physical chemistry of the peri- 
ostracum in Striatura as compared to the other 
taxa might yield highly significant information. 

In conclusion the grossly similar shell 
sculpture of these four taxa show several signifi- 
cant differences in mode of formation and com- 
position. Ebdended studies on the ribbed pu- 
pillids, small polygyrids, streptaxids, and helicids 
might yield equally interesting results. 


Figures 1 through 12 were taken during a fac- 
tory demonstration of a JEOLCO SEM, and fi- 
gures 13 through 18 were taken on a Cambridge 
S4-10 provided Field Museum of Natural History 
by NSF grant BMS72-02149. I am grateful to Mr. 

Fred Huysmans for the excellent photographic 
prints, to Dorothy Karall for mounting them into 
prints, and to Sharon Bacoyanis for help with 
manuscript preparation. 


Baker, H. B. 1927. Minute Mexican Land Snails. P>-iic. Acad. 

Nat. Sci.. Phiiadelphia 1927: 223-246. pis. 15-20. 
Baker. H. B. 1928a. Planogi/ra asti'risciix (Morse). The 

NwitUu.-i. 41(4): 122-123. 
Baker. H. B. 1928b. Minute American Zonitidae. Pruc. Acad. 

Nat. Sci.. Philadelphia. 1928: 1-44, pis. 1-8. 
Baker. H. B. 19.3.5. Review of the Anatomy of the Pupillidae 

and Related Groups. In Manual of Conchology, (2) 28: 

Giusti, F. 1973. Notulae Malacologicae XVIII. I Molluschi ter- 

restri e salmastri delle Isole Eolie. Lavori Delia Sac. 

Italmna Biogeog.. n. s.. 3: 113-306, pis. 1-16, 2 tables, 39 text 

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

of Mexico). Acad. Nat. Sci.. Philadelphia. Monog. 3, 2(1): 

i-vi, 1-.520, figs. 1-281. 
Pilsbry. H. A. 1948. Land Mollusca of North America (North 

of Mexico). Acad. Nat. Sci.. Philadelphia, Monog. 3, 2(2): i-x- 

Ivii, 521-1113, figs. 282-585. 
Solem. A. 1970. Malacological Applications of Scanning Elec- 
tron Microscopy. I. Introduction and Shell Surface Features. 

ne Veliger 12: 394-400, pis. 58-60, 1 table. 
Solem. A. 1974. The Shell Makers: Introducing Mollusks. New 

York: John Wiley, pp. xii. 289. 
Solem, A. 1977. Radiodiscus hubrichti Branson, 1975, a 

synonym of Striatura (S.) pugetensis (Dall, 1895) Mollusca: 

Pulmonata: Zonitidae). Vie Naiitilm 91(4) in this issue. 
Solem, A. hi Press. Systematics of non-marine gastropods. 

other than Basommatophora. /« Pulmonata, vol. 2, 

Systematics, Evolution and Ecology. Academic Press. 


Several complete original sets of 
Johnsonia, vol. 1 to vol. 5, no. 50 $130 each; 
postpaid (unbound). 

Several incomplete sets (pt. 5 absent) of 
Dall's Tertiary Fauna of Florida, 1890-1895 
(Gastropods and some bivalves). Send for 
price list. 

Write: Dept. G., The Nautilus. Box 4208 
Greenville, Delaware 19807. 

156 The Nautilus 

October 27, 1977 

Vol. 91 (4) 

We deeply regret to announce the tempo- 
rary suspension of the Department of Mollusks 
at the Delaware Museum of Natural History 
effective November 15, 1977. Public exhibits at 
the museum will remain open. However, the 
Curator and Assistant Director of the 
Museum, R. Tucker Abbott, and the Assistant 
Curator of Mollusks, Russell H. Jensen, as a 
consequence, will be leaving their positions. 
Professional malacologists are invited by the 

Director to continue to use the facilities of the 
museum. Those wishing malacological informa- 
tion may address Dr. Abbott at P.O. Box 4208, 
Greenville, Delaware, 19807 and Mr. Jensen at 
R.D. 1, Box 55, Chadds Ford, Pennsylvania, 

These events will not adversely affect the 
publication of The Nautilnfi. Indo-Pacific 
Mdlhi.'^cn, The Standard Catalog of Shells or 
publications of American Malacologists, Inc. 


We regret to announce the sudden death of 
George E. Radwin, Curator of Mollusks at the 
San Diego Museum of Natural History. George 
was born August 20, 1940, at Far Rockaway, 
N.Y., and died of a heart attack at the age of 37, 
on September 30, 1977, in San Diego. Most of his 
research was on the ta.xonomy of the Muricidae 
and Columbellidae. He was senior author of the 
recent book, Murex Shells of the World. He 
received his Ph.D. in 1968 from The George 
Washington University, and went to San Diego 
in 1970. He is survived by his wife, Rodda, to 
whom all malacologists send their sincere con- 

Henning M. Lemche, former head of the 
Department of Mollusks, of the Zoological 
Museum, University of Copenhagen, Denmark, 
died August 4, 1977, after a brief illness. Dr. 
Ivemche was an outstanding malacologist, well- 
known for his works on nudibranchs and 


Isabelle E. Welch of Fails Church, Virginia, 
an ardent shell collector and partner in The Shell 
Cabinet, died on August 15, 1977. She was a 
former employee of the U.S. Navy, a member of 
the A.M.U. and several shell clubs. Miss Welch 
produced several taped travelogs of her shelling 
experiences in the Bahamas and the Galapagos. 


Stanford University Collections Ti'ansferred 
to the California Academy of Sciences 

The moUuscan shell collection, the type 
specimen collection, and a major part of the in- 
vertebrate fossil collection of the Department of 

Geology, Stanford University, have been trans- 
ferred on indefinite loan to the Department of 
Geology, California Academy of Sciences. All 
enquiries regarding these Stanford collections 
should be directed to the Academy. The com- 
bined Academy and Stanford collections are 
now available for study. The shell and fossil 
collections are housed separately, and both col- 
lections have work space and other facilities for 

The combined Academy — Stanford shell col- 
lection, containing an estimated one million 
specimens, is of world-wide scope, but is 
especially rich in marine species from the 
Eastern Pacific and land snails from Western 
North America. The fossils transferred from 
Stanford to the Academy include the Cenozoic 
stratigraphic collection and the systematic col- 
lection of fossil cephalopods and echinoids. The 
combined Academy — Stanford fossil collection 
contains about one million specimens (mostly 
mollusks), principally from Cenozoic and Late 
Mesozoic rocks of the Pacific Coast of North 
America (Alaska to Mexico), The combined Aca- 
demy — Stanford type collection, housed in a 
separate room, contains several thousand spe- 
cimens including primary and secondary' types 
of living mollusks, and fossil invertebrates 
(mostly mollusks), vertebrates and plants. 

Peter U. Rodda 

C(illfonii(t Academy of Sciences 
San Francisco. Califoniia 9J,11S 


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Mill. WIK" .V'lIi'iMiMIl' 

yH 17XX 

-.w «• .