275 



margin decidedly more widely rounded than the posterior mar- 

 gin ; beaks obviously elevated above the general curvature ; car- 

 dinal teeth double, distinct. Say. Des. terr. fluv. shells. Hinge 

 margin nearly on a straight line ; anterior cardinal teeth the 

 larger and more prominent; lateral teeth not very prominent ; 

 inferior margin well rounded ; striae very fine ; color light yellow. 



Long. 0.65; lat. 0.45 ; diam. 0.19 inches. 



Localities. Kentucky, (Say.) Columbus, O. and Arkansas, 

 (Anthony.) Mohawk, Herkimer County, N. Y. (Lewis.) 



This shell is more transverse than even the C. similis Say. 



Its outline is somewhat similar perhaps to the C. detruncata ; 

 it is otherwise, however, widely different, being not only more 

 transverse, more inflated, but also of a different and more fragile 

 texture. 



9. CYCLAS SPELERICA Anthony, Mss. 

 Cabinet of J. G. Anthony. 



Shell. Small, globose, not elongated ; 

 posterior and inferior margins rounded ; 

 beaks inclined towards the anterior, very 

 large, prominent, and well rounded ; an- 

 terior extremity somewhat rounded, very 

 much narrower than the posterior one ; 

 lines of growth fine and regular. Epi- 

 dermis glossy ; color greenish brown ; hinge margin curved ; 

 cardinal teeth double, small, but distinct; posterior cardinal teeth 

 prominent; anterior one nearly obsolete ; interior light blue. 



Long. 0.29 ; lat. 0.25; diam. 0.20 inches. 



Locality. Loraine County, O. (Anthony.) 



This rare species is not much like any of our American spe- 

 cies ; it approaches nearer the C. nucleus of Europe than to any 

 other shell : it differs much, however, not only in size but also 

 in globosity. 



Compared to the C. cardissa, it is more inflated, the margins 

 are less spherical, and the beaks are more prominent. It is less 

 equilateral and more inflated than the C. ovalis, and less elon- 

 gated and more inflated than the C. rosacea. 



