3Ionograpli of the LamcUihranchiata. 217 



Modiolopsis anodontoides — (Conead ) . 



General figure subelliptical, very convex ; beak elevated, with a 

 strong angular ridge extending to the posterior basal margin ; cardinal 

 margin nearly straight; posterior extremity obliquely truncated ; base 

 contracted just below or a little posterior to the beak ; surface marked 

 by strong concentric striae ; length a little more than twice the height. 

 It is readily recognized by its great umbonical elevation, and the prom- 

 inent oblique cai'ina extending from the beak to the posterior basal 

 extremity. 



This species was placed by Conrad in the genus Cypricardites, and 

 removed by Hall into the genus Modiolopsis, where I have left it, for 

 want of knowing the hinge line and internal structure. It is most 

 likely, however, that it belongs to neither of these genera. 



It is found opposite the foot of Fifth street, in Kentucky, and oppo- 

 site the mouth of the Little Miami river. Its range, so far as is 

 known, is limited between low water-mark and 200 feet above. It is 

 not common, by any means. 



' Modiolopsis tnincatus — (Hall, 1847). 



Oblique, transverse, subtrapezoidal ; the cardinal and basal mar- 

 gins diverging fi*om the anterior extremity, convex ; beaks near the 

 anterior extremity, with an obscure elevated ridge extending obliquely 

 to the base ; posterior extremity obliquely truncate ; muscular impres- 

 sion very distinct, a little in advance of the beaks, and at the anterior 

 extremity, in the cast, projecting beyond the margin. 



It differs from 31. modiolaris, in that it is proportionally broader ; the 

 beaks are closer to the anterior extremity, while the muscular impres- 

 sion seems to be placed upon the very margin of the shell. 



The shell of this species is unknown. 



It is found at the quarries back of Cincinnati, from 300 to 450 feet 

 above low water-mark. Its exact range is unknown, and good casts 

 are very rare. 



Modiolopsis termincdis — (Hall, 1847). 



Subcylindrical, elongated, very gradually expanding from the ante- 

 rior extremity ; beaks subacute, near the anterior extremity ; surface 

 smooth, or with fine concentric stride. 



In the perfect shell the beaks extend nearly, or quite, as far as the 

 line of the anterior margin. 



This fossil has only been found as a cast, and it is by no means cer- 



