CONCHOLOGIA CESTRICA. 



P. lapidaria, SAY. 



Cyclostoma lapidaria, Say, Jour. Acad. Phila., I., 1817. 



' She11 ' sub - um bilicate ; whorls 6, obsolete- 

 ly, and transversely, wrinkled ; aperture 

 longitudinally ovate-orbicular, more than 

 one-third the length of the shell. H. 6, 

 W. 2^, mill. 



Idngual Dentition of P. lapidaria, [Stimp.] 

 Pig, 174, 



Station, under stones, near water. New Garden, 

 Chester County ; not common. 



P. lustrica, SAY. 



Paludina lustrica, Say, Jour. Phila. Acad., II., 1821. 



p. lustrica. Shell, conic; whorls convex; aperture 

 [w. G. B.] oval-orbicular ; upper margin of the lip not 

 1K '* appressed to the last whorl ; umbilicus rather 



J3 large, rounded. H. 5, W. fy, mill. 



Station, shores of the Delaware River. 

 (Tryon.) 

 OBS. Possibly, the young of the preceding species. 



Genus SOMATOGYRUS, GILL, 1863. 



Shell, short, sub-conic, striate, thin, or moderately 

 thickened ; spire small ; aperture large, broad-ovate, 

 oblique ; operculum thin, sub-spiral. 



Animal, with the foot oblong, broadly rounded be- 

 hind, and auricled in front ; rostrum broad ; tentacles 

 long, slender, and pointed ; eyes at the outer sides of 



