80 CONCHOLOGIA CESTRICA. 



Station, Schuylkill River, and Brandywine Creek, 

 Chester County ; common. 



Jjingual Dentition of A. limosa. [Stimp.] Opercuhtm of A. 



?i 166, limosa. [Stunp.] 



Fig. 167. 



A. decisa, HALDEMAN, Mon. Lim., 1842. 

 A. decisa. Shell, short, conical, smooth, shining ; 

 ^Fi G 16 8 ] whorls 5 ; base slightly perforated ; aperture 

 dilated, semicircular ; color pale green ; slightly 

 translucent. H. 4, W. 2^, mill. 



Station, Brandywine Creek, Chester County ; 

 not common. 



A. grana, SAY. 



Paludina grana, Say, Jour. Acad. Phila., II., 1822. 

 A. grana. Shell, very small, . conic-ovate ; whorls 5, 



[\V. G. B.I 



Fig. 169. convex, smooth ; aperture orbicular, sub-an- 

 gular; umbilicate. L. 2, W. i l / 2 , mill. 



Station, in ponds, on fallen leaves. Picker- 

 ing Creek, Chester County ; abundant. 



Genus BYTHINELLA, MOQUIN TANDON, 1851. 



Shell, elongated-ovate, turreted ; umbilicus generally 

 closed ; apex obtuse ; aperture oval, or rounded, slightly 

 thickened. 



Animal, with the foot rather long, narrow, and round- 

 ed behind; tentacles setaceous and pointed; verge bifid; 

 the longer branch not coiled about the shorter one ; 

 operculum sub-spiral ; concealing the posterior part of 

 the foot. 



