CONCHYLIA— DZTHFi?^. xlvii. 



56. Cyclas. 



* suborbiculares , cequilaterales. 

 nearly orbicular, and equilateral, 

 rivicola, opaca, striis, transversis regularibus. 



opake, with regular transverse striae, 

 cornea, .subdiaphana, transversim substriata. 



somewhat transparent, with irregular transverse 



striae. • 

 lacustris, peUucida, IcBvis, umbonibus tuberculosis. 



transparent and smooth, with the beaks tubercular, 



** obliqu(B, inaquilaterales. 

 oblique, and inequilateral, 

 aranica, transversim sulcata, umbonibus tumidis. 



transversely grooved, with the beaks prominent, 

 pusilla, transversim substriata, umbonibus depressis. 



irregularly striate transversely, with the beaks 



depressed. 



