AMNICOLIDiE. 45 



margin in one plane, slightly perforate. At- 

 lantic coast of United States, Somatogtrus.* 



Shell subglobular, thick, smooth, imperforate ; 

 aperture ovate, outer lip diffuse and project- 

 ing anteriorly, so that the peristome is not 

 continuously in the same plane. Pacific 

 slope of United States, . . Fluminicola. 



B. Shell sculptured. 



Shell elongated, carinated or plicated, perfo- 

 rated ; aperture small, effuse and sinuated 

 at the base, .... Tryonia. 



*I do not think that Dr. Stimpson's genus GtlUa can be 

 separated from Somatogyrus. The lingual dentition does 

 not in my opinion afford a sufiSciently reliable distinctive 

 character, and I am not even entirely satisfied that the type 

 of the latter — S. depressus, nob, — is specifically distinct 

 from Melania Integra, Say, which Dr. Stimpson supposes to 

 belong to his genus Gillia. 



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