282 



22. Cyclas soLiuuLA Nobis. Boat. S. N. H. Proc. iv. 158. 

 Cabinet of the B. S. N. H. 



Shell Vide Bost. S. N. H. Proc. iv. 158. 



Localities. New River, Va. (Anthony.) Black River, 

 Highland County, O. (Anthony.) 



This species is very common in Ohio, and as well as the 

 C. distorta is frequently labelled C. similis. Comparing it, 

 however, to C. similis., it is much more broad, less elongate, and 

 stronger; the striations are deeper and more regular. The 

 hinge margin is curved ; whereas, in C. sitnilis it is nearly a 

 straijiht line ; the teeth themselves are more robust. 



23. Cyclas gigantea Nobis. Bost. S. N. H. Proc. iv. 157. 

 Cabinet of the B. S. N. H. 



Shell. Vide Bost. S. N. H. Proc. iv. 157. 



Localities. Tuscarora Creek, Franklin County, Penn. (Hal- 

 deman.) Cassadaga Creek, Chatauque County, N. Y. (Red- 

 field.) 



This is our largest known American species, and is as yet but 

 rare. 



Compared to the C. similis, it is found to be more full, less 

 elongated, broader, the margins are more rounded, the cardinal 

 teeth are stronger, more heavily striated, of a heavier texture, 

 and of a different color. 



24. Cyclas ponderosa Nobis. Bost. S. N. H. Proc. iv. 157. 

 Cabinet of the B. S. N. H. 



Shell. Vide Bost. S. N. H. Proc. iv. 157. 



Locality. Lake Superior, (Agassiz.) 



With the exception of the C. gigantea, this is our largest 

 known American species. Hitherto single valves alone have 

 been found. Compared to the C. gigantea, it is rather more 

 inflated, the beaks are higher, and tlie margins are not so well 

 rounded. Compared to the C. aurea, it is broader, the hinge 

 margin is less curved, though the color is about the same. 



