Monograj)h of the Lamellibrancluata. 227 



tends from in front of the beak behind the anterior adductor impres- 

 sion, leaving a furrow in the cast; pallial impression entire; (occa- 

 sionally one small cardinal tooth beneath the beak); surface smooth or 

 concentrically lined. 



Aiiodonfopsis (?) unio)ioides — (Meek). 



Shell thin, subovate, rather compressed, most convex slightly above 

 and in advance of the middle ; anterior margin regularly rounded ; 

 basal margin forming a broad semi-elliptic curve, or nearly straight 

 along the middle ; posterior margin sloping from the posterior extrem- 

 ity of the hinge above, and rounded into the base below ; hinge line 

 straight, apparently rather short ; beaks depressed nearly to the hinge 

 margin, small, and placed between one fourth and one fifth the length 

 of the valves from the anterior end. Surface showing only a few 

 distant subimbricating marks of growth. 



Length, 1.75 inches; height, 1.14 inches; convexity, 0.63 inch. 



Found about 350 feet above low water-mark, at Cincinnati. Range 

 not known. Very rare. 



Some of the casts that are usuaMy supposed to belong to the genus 

 Modlolopsis probably belong to this species. I do not believe, how- 

 ever, that it belongs either to the gexixi^ Anodontopsis ov Modlolopsis ; 

 indeed, I think it is very far removed, at least from the former, but as 

 I don't know into what genus it should be placed, I have left it where 

 Prof. Meek has left it. 



Anodontopsis f Milleri — (Meek). 



Shell ovate, rather compressed or only moderately convex, the great- 

 est convexity being a little above and slightly in advance of the mid- 

 dle, extremities more or less narrowly rounded, basal margin longi- 

 tudinally semi-elliptic in outline, the most prominent part being near the 

 middle; cardinal margin sloping from the beaks at an angle of 130 to 

 135 degrees, and rounding into the lateral margins ; beaks only mod- 

 erately prominent, somewhat obtuse, and not very convex, placed 

 more than one third the length of the valves from the anterior end. 

 Surface smooth, or only with obscure lines of growth. 



Length of a medium sized adult specimen, 0-83 inch; height.. 0-59 

 inch ; convexity, 0'30 to 33 inches. 



The hinge may be characterized as having one rather well defined, 

 subtrigonal, or somewhat obliquely extended cardinal tooth under the 

 beak of the right valve, and a corresponding pit under the beak of the 



