160 



inequilateral!, striis incrementi instructa, epidermidcfusca, um- 

 bonibus parvis, iion elevatis. Long. 0.46 ; lat. 0.38 ; diam. 

 0.21. Hah. from the Wabash River. (Haldeman) 



Remarks. This species differs from the C.fahalis Nobis, in 

 being more compressed, and also less heavily striated ; the beaks 

 are less tumid. The hinge margin is somewhat more spherical, 

 the teeth larger and more acute. The whole shell seems to be 

 of a somewhat lighter texture. 



Cyclas secueis. C. testa minuta, rhomboidea, complanata, 

 tenui, fragili, subequilaterali, umbonibus magnis, elevatis. Long. 

 0.29; lat. 0.23; diam. 0.17. Hab. Massachusetts. 



Shell very small and fragile, rhomboid form ; beaks large and 

 tumid. Color light straw ; striations not visible to the naked 

 eye. 



Animal of a bright pink color, imparting a pinkish hue to the 

 shell ; syphons of about the same length, rather small, and of a 

 pink color ; foot long and very retractile. 



Remarks. I have found this shell very frequently at Fresh 

 Pond, and in the Cambridge Meadows during the summer months 

 and at other seasons occasionally. It lives in company with the 

 C. truncafa Linsley, and the C. elegans Adams. 



This species seems to be related to no other species, but the 

 C. truncata Linsley, from which, however, it is distinguished by 

 its rhomboidal form and in being more elongated and less in- 

 flated. The animal is very lively and crawls about like a gas- 

 teropod. Cabinet of the Boston Society of Natural History. 



Cyclas cahdissa. C. testa globosa, ventricosa, tenui, fragili, 

 subequilaterali, umbonibus magnis, rotundatis, approximatis. 

 Hah. Massachusetts. 



Shell very much inflated, beaks prominent and well rounded. 

 Color yellow on the margins, but gradually merging into dark 

 olive green on the beaks. Found in Fresh Pond, near Cam- 

 bridge, and at Salem. 



Remarks. This species is very nearly allied to the C. trun- 

 cata of Linsley, but is different in being more especially inflated 

 and having less prominent beaks : the outline is also different, 

 the C. truncata being posteriorly more angular, than the C. 

 cardissa. 



