155 



Mr. Prime presented a number of new species of Cycla- 

 didce, with descriptions. 



1. GENUS CYCLAS. 



Cyclas albula. C. testa magna, forti, obliqua, subglobosa, 

 tumida, complanata, subequilaterali, postice acuta, flava, striis 

 concenlricis instructa, umbonibus magnis, non elevatis. Long. 

 0.50 ; lat. 0.41 ; diam. 0.33 inches. Hab. Lake Superior. 

 (Agassiz.) 



This shell resenables somewhat the C. flava Nobis, but is 

 larger, less fragile and of a more greenish color. Found gene- 

 rally with beaks eroded. Cabinet of the Boston Society of 

 Natural History. 



Cyclas acu3IINAta. C. testa fragili, rhomboidea, depressa, 

 inequilateral], postice abrupta, alba, nitida, striis concentricis in- 

 structa, umbonibus parvis, depressis. Long. 0.52 ; lat 0.47 ; 

 diam. 0.35 inches. Hah. Lake Superior. (Agassiz.) 



This shell, somewhat similar to the C. similis Say, is less de- 

 pressed, less elongated, and of a darker color. Cabinet of the 

 Boston Society of Natural History. 



Cyclas rosacea. C. testa minuta, tenui, fragili, tumida, ven- 

 tricosa, subequilaterali, postice dilatata, striis concentricis tenui- 

 ter instructa, nitida, rosacea, umbonibus parvis, perelevatis. 

 Long. 0.28 ; lat. 0.23 ; diam. 0.16 inches. Hah. Pennsylvania. 



This shell, found in the Schuylkill, seems to be closely allied 

 to the C. securis Nobis, from Massachusetts, but the posterior 

 is less abrupt ; the beaks are more tumid. 



Cyclas detruncata. C. testa ovata, complanata, truncata, 

 elongata, inequilaterali, postice abrupta, antice acutissima, umbo- 

 nibus parvis non elevatis, epidermide olivaceo. Long. 0.48 ; 

 lat. 0.36 ; diam. 0.24 inches. Hah. Pennsylvania. 



This shell, likewise from the Schuylkill, is remarkable for the 

 suddenness with which the marginal outline forms the anterior of 

 the shell. 



Cyclas flava. C. testa compressa, subovata, fragili, ine- 

 quilaterali, epidermide flava, striis concentricis instructa, pos- 



