252 CO^CHYLIA—DITHYRA. 56. 



Turton, Linn. Sjst. iv. p. 187. 

 Wood, Conch, p. 152. 

 Dillwyn, Descript. Catal. p. 106. 

 Turton, Conch. Diet. p. 167. 

 Mus. nost. In slow streams and stagnant ponds. 



Shell about the eightij of an inch long, and a little broader ; 

 very convex thin and transparent, horn-color or yellowish, often 

 covered with a rough coat, with obscure close-set transverse stria; : 

 beaks near one end, not tumid as in the last species. 



From the young of Cyclas amnica it is distinguished by its 

 greater convexity, and the want of regular grooves between the 

 raised striae ; and from the other species by its oblique outline, 

 not having the beaks central. 



