284 



This is our most spherical and globular species, and owing 

 to these distinctive marks, it is not very likely to be confounded 

 with any fcther. 



29. CYCLAS FLAVA Nobis. Bost. S. N. H. Proc. iv. 155. 

 Cabinet of the B. S. N. H. 



Shell. Vide Bost. S. N. H. Proc. iv. 155. 

 Locality. Sault Ste Marie, (Agassiz.) 



This species seems to bear no particular affinity to any other ; 

 it is remarkable for its uniform yellowish color. 



30. CYCLAS MODESTA Notts. Bost. S. N. H. Proc. iv. 159. 



Cabinet of the B. S. N. H. 



Animal. Tubes light reddish yellow. 



Shell. Vide Bost. S. N. H. Proc. iv. 159. 



Localities. Greenwich, Washington County, N. Y., Hoosack 

 River, (Ingalls.) Pennsylvania, (Haldeman.) Saratoga Lake, 

 N. Y. (Nobis.) 



This species is somewhat similar to the C. distorta ; it differs, 

 however, in being less inflated and less broad, also in being 

 decidedly less heavily striated. 



The animal is very lively. 



31. CYCLAS SIMPLEX Notts. Bost. S. N. H. Proc. iv. 159. 



Cabinet of the Ac. Nat. Sc. 



Shell. Vide Bost. S. N. H. Proc. iv. 159. 



Locality. Fox River, 111. (Haldeman.) 



This species, of which one valve only has been found, and 

 that a dead shell, does not seem to be very closely allied to any 

 other. Compared to the C. modesta, it is more inflated ; the 

 beaks are more tumid ; the margins are more rounded, and the 

 posterior cardinal tooth double in the right valve and single in 

 the C. simplex, is double in the C. modesta. 



