242 NEW YORK STATE MUSEUM 



Genus bythinella Moquin-Tandon. 1855 

 Shell elongated and pyriform; imperforate; apex obtuse; aper- 

 ture oval; lip simple; operculum corneous. 



Bythinella obtusa (Lea) Binney 1865 (Fig. 166). P a 1 u d i n a 

 obtusa Lea (1844. Philos. soc. Phil. Trans. 9:13). Bythin- 

 ella obtusa Binney (1865. Smith. Misc. coll. no. 

 144, p. 70) 



Shell small, subcylindric, comparatively thin; five 



whorls; spire very short, giving the shell a truncated ap- 



tmnliia^ Ob- pearance; apex obtuse; sutures well defined; delicate 



tusa. x3 growth lines may be seen with a lens; the aperture is 



small and round; the umbilicus narrow and deep. 



Found in the Goat island gravel pits. 



Genus pomatiopsis Tryon. 1862 



Animal with a broad, short foot^ and short pointed tentacles. 

 Shell thin and smooth, having a produced spire; aperture oval, and 

 provided with an operculum. 



Pomatiopsis lapidaria (Say) Tryon 1862 (Fig. 167). C y c 1 o s - 

 toma lapidaria Say (1817. Acad. nat. sci. Phil. Jour. 1:13). 

 Pomatiopsis lapidaria Tryon (1862. Acad. nat. sci. 

 Phil. Proc. p. 452) 



Shell conic; spire high, seven whorls, well rounded and trans- 

 versely wrinkled; sutures impressed; aperture rounded 

 and about one third the length of the shell; subumbilicate. ■' \ 



. ^ A 



Found at Foster's flats. This species is not found in - i 

 any of the other deposits. ^^( 



The locality at Foster's flats, where this little shell is 



found, is just below the old fall. At the present time, the -^^^ j^y p^. 



1 1 1- r -n 1 -1 • 1- 1 matiopsis lapi- 



only locality tor r. lapidaria thus far discovered dana. x3 

 along the river is on the rocks in the constant rain of spray, bel'ow 

 the present fall. 



Genus valvata Miiller. 1842 



Animal with a bilobed foot, simple mantle and feather-like gills, 

 protected by a long, slender respiratory lobe. The shell is discoidal, 

 has a deep umbilicus and is provided with an operculum. 



