CYllENA. 



17 



aud more full and the epidermis is darker and without auy per- 

 pendicular radiations. 



9. Cyrena fortis, Prime.— Shell trigonal, tumid, solid, 

 teral ; anterior side shorter, 

 rounded ; posterior side sub- 

 truncated ; valves moderately 

 full, interior dark violet ; beaks 

 large, inclined anteriorly, ap- 

 proximate at apex, slightly 

 eroded ; strire deep, regular, 

 epidermis shiny, varying from 

 green to browuish-green ; hinge 

 margin somewhat broad, curv- 

 ed ; cardinal teeth unequal, 

 divergent, simple ; lateral 

 teeth strong, anterior tooth 

 nearer to the cardinal teeth, 

 conical, posterior tooth, elon- 

 gated ; sinus deep, curved and 

 acute at extremity. 



Long. 2.38; Lat. 1.77; 

 Diam. 1.22 inches. 



Long. 62; Lat. 47; Diam. 

 .32 mill. 



inequila- 



C. fortis. 



Hah. South America, in Ecuador. (Cabinets of Smithsonian Institution 

 aud Prime.) 



Cyrena fortis, Prime, II. Conch. IX, 1861, 355— X, 1862, 387, pi. xiv, 

 f. 2. 



This fine and rare shell presents great similarity to G. radiala, 

 it differs, however, in being larger, less equilateral, transversely 

 longer, the beaks are a little fuller, the hinge is not so strong or 

 so broad aud the epidermis has more lustre ; the i)erpcndicular 

 radiations common to some specimens of C. radiata are wanting. 



10. Cyrena olivacea, Carpenter. — Shell irregular, subtrigonal, 

 somewhat compressed, subequilateral ; anterior side shorter, rounded, pos- 

 terior narrower, very angular ; beaks large, prominent, inclined towards 

 the anterior ; valves very little convex, interior violet, darker on the mar- 

 gins ; exterior surface irregular, striae coarse ; epidermis rich olive-green ; 

 Liuge-margin much curved, three unequal rather small cardinal teeth ; 

 2 



