Helisoma eucosmium 



25 



Table 1. Freshwater mollusks of upper Town Creek, Brunswick County, 

 North Carolina, 1994. 



Gastropods 



Bivalves 



Viviparidae 



Campeloma decision (Say) 

 Hydrobiidae 



Amnicola limosus (Say) 



Gillia altilis (Lea) 

 Physidae 



Physella hendersoni (Clench) 

 Planorbidae 



Micromenetus dilitatus (Gould) 



Helisoma eucosmium (Bartsch) 



Planorbella trivolvis (Say) 

 Ancylidae 



Laevapex fuscus (C. B. Adams) 



Unionidae 



Pyganodon cataracta (Say) 

 Villosa delumbis (Conrad) 

 Ligumia nasuta (Say) 

 Unknown taxa of the 

 Elliptio complanata and 

 Elliptio icterina complexes 



Corbiculidae 



Corbicula fluminea (Muller) 



Sphaeriidae 



Eupera cubensis (Prime) 

 Musculium securis (Prime) 

 Unidentified sphaeriids 



a problem generated and sustained by years of inconclusive taxonomic 

 studies resulting from the great similarity in chonchology and anatomy 

 existing within a genus complex of worldwide distribution (Hubendick 

 1955, H. B. Baker 1960). While taxonomic and systematic problems 

 are common in the freshwater gastropods, the need for nomenclatural 

 stability within the tropical planorbids is a matter of great medical 

 and economic importance because these snails are intermediate hosts 

 of the human parasite Schistosoma mansoni. 



In response to a petition by Wright (1962), the International 

 Commission on Zoological Nomenclature (1965) issued Opinion 735, 

 ruling that Biomphalaria is to be given precedence over the generic 

 names Taphius, Planorbina, and Armigera when any or all of these 

 names are considered to apply to the same genus. Under this ruling, 

 Fuller's (1977) binomen would be valid only if Taphius is determined 

 to be separable from Biomphalaria at the genus level. Bypassing this 

 issue, Burch (1982, 1989) stated Helisoma eucosmium may be a "form 

 or juvenile" of Helisoma anceps (Menke, 1930) and, therefore, did 

 not grant it specific status. Based on shell morphology and the reproductive 

 maturity of the material collected from Town Creek, we find no evidence 

 to support this possibility. Although the very oblique aperture of H. 

 eucosmium is suggestive of the Biomphalaria group, the lack of vertically 

 depressed whorls is not; therefore, we provisionally accept Baker's 



