CONCHOLOGIA CESTRICA. 6/ 



Lingual Dentition of P. anciUaria. [W. G B.J 



Fig, 130, 



P. heterostropha, SAY, Jour. Acad. Phila. F. S., II., 

 1821. 



Shell sub-ovate, pale yellow to chestnut; 

 whorls 4, the first large, the rest very Fig, m, 

 small ; apex abrupt, acute ; aperture oval, 

 three-fourths the length of the shell ; lip 

 slightly thickened, within, pearly. H. 16, 

 W. 9, mill. 



Station, springs and small streams. Chester County; 

 very abundant. 



P. gyrina, SAY, Jour. Acad. Phila. F. S., II., 1821. 



Shell, oblong ; whorls 5-6, gradually acu- 

 minated; aperture a little more than half the 

 length of the shell ; outer lip thickened within 

 the margin. H. 17, W. 10, mill. 



Station, streams. Western Pennsylvania. 



OBS. Sometimes confounded with the 

 preceding species. 



