70 



CONCHOLOGIA CESTRICA. 



II. trivolvis. 



[W. G. B.] 

 Fig, 138, 



H. trivolvis, SAY. 



Planorbis trivolvis, Say, Nich. Encyc., 

 Amer. Ed., 1816. 



Shell, pale brownish-yellow, sub-cari- 

 nate above and beneath, especially the 

 inner whorls; whorls 3-4, fine ridge- 

 striate ; spire concave ; aperture large ; 

 lip thickened, reddish within, vaulted on 

 its shorter side ; umbilicus wide, shallow. 

 H. 8, W. 17-13, mill. 



Station, ponds and streams. Chester 

 County; common. 



H. trivolvis, Var. fallax, HALD., Lim., 1842. 



H. trivolvis, Var. fallax. [W. G. B.] 



Fig, 139, 



Shell, thin, tranlucent, carinate below ; umbilicus 

 very shallow; whorls 3, obsolete-striate ; lip acute, 

 margined; aperture ovate. H. 7, W. 13-10, mill. 



Station, Schuylkill River, Chester County. 



H. bicarinata, SAY. 



H.Mcannata. Planorbis bicarinatus, Say, Nich. Encyc., 

 [W.G. B.] Amer. Ed., 1816. 



Fig, 140. 



Shell, pale brownish-yellow; whorls 3, 



carinate on both sides ; aperture large ; lip 

 sub-revolute, arched above and below; 

 within chestnut, with two arched lines an- 

 swering to the carina. H. 6, W. 12-9, 

 mill. 

 Station, ponds and streams. Chester County; common. 



