268 SIX NEW SPECIES 



marks of growth — cardinal tooth large, prominent, serrated ; 

 in the left valve deeply divided by the entering of the oppo- 

 site tooth — lateral tooth abrupt — ^posterior cicatrices distinct, 

 anterior cicatrices also distinct — cavity of the beaks rather 

 deep — nacre pearly white and iridescent in the posterior mar- 

 gin. 



Remarks. — The characteristics of this little shell are its 

 angulated posterior slope giving it in some measure the form 

 of a donax, and its large divided cardinal tooth. Its beautiful 

 angulated beaks approach so closely together as scarcely to 

 admit the edge of a piece of fine paper. 



In its most prominent character, the peculiar angulated 

 slope, it most resembles the ovatus of Say, but differs greatly 

 in the size, the ovatus being four or five inches in breadth, 

 and very much more inflated. The latter has a double car- 

 dinal tooth in each valve ; the donaciformis only in the left 

 valve. 



4. Unio Ellipsis. Plate IV. fig. 4. 



Testa figuram ellipseos hahpnt.e., longitudinali, ventricosa; valvulis 

 crassis, mnbonibus fere terminalibus ; dentibus grandibus et distinctis. 



Shell elliptical, longitudinal, ventricose ; valves thick ; beaks nearly 

 terminal; teeth large and well defined. 



Hab. Ohio. T. G. Lea. 



My Cabinet. 

 Cabinet of T. G. Lea. 

 Cabinet of Prof. Vanuxem. 

 Cabinet of Mr Nicklin. 

 Peale's Museum. 

 Cabinet of the Academy of Natural Sciences. ' 

 Diam. 1-3, Length 1-7, Breadth 2-3 inches. 



Shell very thick, ventricose, margin elliptical — substance 

 of the shell thick and ponderous — ^beaks thick and projecting 



