156 



tice dilatata, umbonibus parvis, depressis. Long. 0.39; lal. 

 0.30 ; diam. 0.21 inches. Hab. Lake Superior. (Agassiz.) 



This shell seems to bear no particular affinity to any other 

 species, but is remarkable for its uniform yellowish gold color. 

 Cabinet of the Boston Society of Natural History. 



Cyclas emarginata. C. testa magna, forti, globosa, tumida, 

 obliqua, postice subtruncata, inequilaterali, triangulari, epider- 

 mide olivaceo, tenuiter striata, umbonibus tumidis, magnis, mar- 

 ginibus abruptis. Dentibus fortibus. Long. 0.48 ; lat. 0.41 ; 

 diam. 0.28 inches. Hah. Lake Superior. (Agassiz.) 



Shell is remarkable for its triangular appearance, and finely 

 striated epidermis. Color, olive green. Interior, bluish. 



Remarks. This species seems to be very nearly allied to a 

 shell from Lake Champlain, supposed, by Professor C. B. Ad- 

 ams, to be the C. rhomhoidea, of Say ; it is different, however, 

 in being less oblique, and in being less heavily striated. Cabinet 

 of the Boston Society of Natural History. 



Cyclas gracilis. C. testa magna, tenui, fragili, subglobosa, 

 complanata, subequilaterali, elongata, postice brevi, alba, nitida, 

 tenuiter striata, umbonibus rotundatis, approximatis. Dentes 

 cardinales parvi, laterales acuti,elongati. Long. 0.60; lat. 0.44; 

 diam. 0.26 inches. Hab. Ohio. (Adams.) 



Shell very fragile ; epidermis, not heavy ; color, light yellow, 

 gradually growing darker from the margins upwards, merging on 

 the beaks into light olive brown. The outline is somewhat simi- 

 lar to that of the C. similis Say, but otherwise the species are 

 very distinct. 



Cyclas tenuistriata. 



Cyclas cornea Lamarck. Adams's Catalogue of Shells in 

 his Cabinet, 1847. 



C. testa subglobosa, complanata, brevi, subequilaterali, postice 

 dilatata, tenuiter striata, umbonibus perelevatis. Dentes parvi. 

 Long. 0.40 ; lat. 0.35 ; diam. 0.26 inches. Hab. Tennessee. 



Shell full, subequilateral, fragile, very finely and irregularly 

 striated ; color pale, greenish yellow. Remarkable for the slight 

 difference existing between the outline of the two extremities. 



Remarks, It is about the same size as the C. cornea, of La- 

 marck, but is less full, rather less fragile, more striated ; the 



