NIAGARA FALLS AND VICINITY 245 



Physa heterostropha Say 1821 (Fig. 174). Limnaea he- 

 terostropha Say (1817-19. Nich. cue. Am. cd. pi. 1, fig. 6). 

 Physa heterostropha Say (1821. Acad. nat. 

 sci. Phil. Jour. 2:172) • %. 



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

 large, the others very small and terminating in an acute \ M 

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

 shell ; outer lip a little thickened, inner lip folded back on Fig 174 Physa 

 the columella, forming a slight callus. heterostropha. 



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



Genus planorbis Guettard. 1756 



The animal of Planorbis 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 1817 (Fig. 175). Planorbis 

 bicarinatus Say (181 7-1 9. Nich. cue. Am. cd. pi. 1, 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- T ... -^ , , . ., < r~> , 



earinatus. x2 Locality, t ound only m the gravel on Goat 



island. 



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



(1817-19. Nich. cue. Am. cd. pi. 1, fig. 5). P. parvus 



Say (1865. Smith. Misc. coll. no. 144, p. 133) ■■ h I 



Shell small, with four whorls crossed by wrinkles or 

 growth lines; concave above and below; body whorl Fig. ra pian- 

 slightly swollen; mouth oblique, with the lip simple. orbis parvus. x2 



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 two 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; 



