CONCHY LI A— DITHYRA. xlvii 



50. Cyclas. 



* suhorbiculares, ceqnilaterales. 

 nearly orljicular, and equilateral. 



1. rivicola, opacn, stiih transversis regularihus. 



opake, with regular transverse striae. 



2. cornea, suhdiaphmiu, transversim substriata. 



somewhat transparent, with irregular transverse 

 striai. 



3. lacustris, pelluciila, Icevis, umhonihus tuberculosis. 



transparent and smooth, with the beaks tubercular. 



** obliqiite, intsrpiilaterales. 

 oblique, and inequilateral. 



4. amnica, transversim sulcata, umbouibus tumidis. 



transversely grooved, with the beaks prominent. 



5. pusilla, Irusiersim substriata, umbonibiis depressis. 



irregularly striate transverselj^ with the beaks 

 depressed. 



