7O CONCHOLOGIA CESTRICA. 
H. trivolvis, SAy. 
Planorbis trivolvis, Say, Nich. Encyc., 
IT. trivolvis, 
[W. G. B.] Amer. Ed., 1816. 
Fig, 138. 
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. 

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H. trivolvis, Var. fallax, HALp., Lim., 1842. 
H, trivolvis, Var. fallax. —[W. G. B.] 
Fig, 139, 

Shell, thin, translucent, 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. 
He bicarinata, sAv 
Ft bicariners. » /lanorbis bicatinatus, Say, Nich) Emeyes 
[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. HHi°6, W. 12-9) 
mill. 

Station, ponds and streams. Chester County ; common. 
