NIAGARA FALLS AND VICINITY 245 



Physa heterostropha Say 1821 (Fig. 174). L i m n a c a h c - 



terostropha Say (1817-19. A'icJi. cue. Am. cd. pi. i, fio-. 6). 



Physa heterostropha Say (1821. Acad. nai. 



sci. Phil. Jour. 2:172) 



Shell oval and smooth, sinistral; whorls four, the first 

 large, the others very small and terminating in an acute 

 apex; aperture large and oval, about half the length of the 

 shell; outer lip a little thickened, inner lip folded back on Figi74Physa 

 the columella, forming a slight callus. heterostropha. 



Localities. Goat island. Whirlpool and Foster's flats. 



Genus PLANORBis Guettard. 1756 



The animal of P 1 a n o r b i s has a broad foot, and long slender 

 tentacles. The shell is dextral and discoidal; the spire depressed, 

 and the whorls numerous and visible on both sides; the aperture is 

 transversely oval, with a thin lip. 



Planorbis bicarinatus Say 181 7 (Fig. 175). Planorbis 



bicarinatus Say (1817-19. Nich. cue. Aui. cd. pi. i, fig. 4) 



Shell sinistral; sharply carinated on both sides; 

 all the whorls may be seen from either side; aper- 

 ture vaulted above, angulated below; surface 

 wrinkled with growth lines at regular distances and 

 surrounded by fine revolving striae. 



Fig. 175 Planorbis bi- -r ■,.. -r- i i-.i i r^ . 



earinatus. x2 Locality. T ouud Only m the gravel on Goat 



island. 



Planorbis parvus Say 1817 (Fig. 176). P. parvus Say 



(1817-19. Nich. cue. Aui. cd. pi. i, fig. 5). P. p a r v u s 



Say (1865. Suiith. Misc. coll. no. 144, p. 133) (0) 



Shell small, with four whorls crossed by wrinkles or 

 growth lines; concave above and below; body whorl Fig. nc, fian- 

 slightly swollen; mouth oblique, with the lip simple. orbi^ parvus. x3 



Locality. Goat island and Foster's flats. 



Class PELECYPODA Goldfuss 

 Genus sphaerium Scopoli. 1777 



General shape of the animal oval, margins plain, united behind 

 and ending in tv/o short siphons, which are joined at their base; 

 mouth oval and small; gills broad and unequal, the inner ones 

 largest; the foot tongue-shaped, triangular, flattened and very ex- 

 tensible. Shell thin, oval, often inflated, with prominent beaks; 



