CONCHOLOGIA CESTRICA. 67 
Lingual Dentition of P. ancillaria.—[W. G. B.] 
Fig. 130. 

P: heterostropha, Sav; Jour, Acad. Phila. F.S., IT; 
1621. 
P. heterostropha, 
[W. G. B. 
whorls 4, the first large, the rest very Fig. 131, 
small; apex abrupt, acute; aperture oval, = 
three-fourths the length of the shell; lip \y 
Shell sub-ovate, pale yellow to chestnut; 
slightly thickened, within, pearly. H. 16, 
W. 9, mill. 
Station, springs and small streams. Chester County ; 
very abundant. 
PrpyrinasSAy, Jour. Acad: Phila /5,,. 1). 1s21. 
~< P. gyrina. 
Shell, oblong; whorls 5-6, gradually acu- wie pj 
Soe 
minated; aperture a little more than half the Fig. 132, 
length of the shell; outer lip thickened within 
the margin. H. 17, W. to, mill. 
Station, streams. Western Pennsylvania. 
Oss. — Sometimes confounded with the 

preceding species. 
