277 



very frequently at Cambridge during the early summer months, 

 in company with C. truncata and C. elegans. The animal is 

 very lively and crawls about like a gasteropod. 



12. Cyclas rosacea Nohis. Best. S. N. H. Proc. iv. 155. 



Cabinet of T. Prime. 



Animal, light pink. 



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



Locality. Schuylkill River, (Richard.) 



Compared to the C. securis, this species is less elevated, more 

 elongated ; the posterior extremity is not so abrupt, the anterior 

 extremity is less full, the whole shell is rather more tumid, and 

 the beaks are not as large. Found in company with C. detrun- 

 cata. 



13. Cyclas cardissa Kohis. Bost. S. N. H. Proc. iv. 160. 



Cabinet of T. Prime. 



Shell. Vide Bost. S. N. H. Proc. iv. 160. 



Locality. Massachusetts, (Prime.) 



Compared to the C. truncata, this species is more globose, 

 less elongated, and the margins are more rounded. Compared 

 to the C. sphcerica, it is also more globose, and the margins are 

 more rounded. 



14. Cyclas pellucida Nohis. Stimpson, N. Eng. Moll. 16. 



Cabinet of the B. S. N. H. 

 Cyclas cahjculata Drap. Adams, Amer. Jour. xl. 277. 



Shell. Transparent, compressed, somewhat rhomboidal, slight- 

 ly elongated, fragile ; posterior margin abrupt, inferior and ante- 

 rior ones well rounded ; beaks central, rising like small tuber- 

 cles, yellow ; lines of growth not visible ; color light gray ; 

 hinge margin nearly on a straight line ; teeth all small ; cardinal 

 teeth united. 



Long. 0.34 ; lat. 0.28 ; diam. 0.18 inches. 



Localities. Vermont, Maine, (Adams.) Canon's River, Cali- 

 fornia, (Anthony.) Greenwich, Washington County, N. Y. 

 (Ingalls.) 



