FRESHWATER AND LAND SHELLS. 43 



Margaritana deltoidea. Plate XIII. fig. 38. 



Testa triangulata, compressa, inizquilaterali; valvulis tenuibus ; natibus prominentibus, ad 

 apices undulatis ; epidermide luted, radiatd; dentibus cardinalibus erectis ; margaritd alba 

 et iridescente. 



Shell triangular, compressed, inequilateral; valves thin ; beaks prominent, undula- 

 ted at the tip; epidermis yellow, radiated; cardinal teeth erect; nacre white and iri- 

 descent. 



Hab. Ohio River, near Cincinnati. T. G. Lea. 

 Scioto. Dr Kirtland. 



My Cabinet. 

 Cabinet of T. G. Lea. 

 Cabinet of Dr Kirtland. 

 Diam. -6, Length -9, Breadth 1-4 inches. 



Shell triangular, compressed, inequilateral, subemarginate at base; 

 substance of the shell thin behind, thicker before ; beaks prominent 

 and strongly undulated at the tip ; ligament short and thin ; epider- 

 mis yellow, with numerous green rays, which are deficient at the 

 beaks ; cardinal teeth erect, double in the left valve, single and conical 

 in the right; lateral teeth obsolete; anterior cicatrices confluent; pos- 

 terior cicatrices confluent ; dorsal cicatrices in the centre of the cavity 

 of the beaks ; cavity of the shell not deep ; cavity of the beaks rather 

 deep and angular; nacre white and iridescent. 



Bern arks. —-This little shell has engaged my attention for some time, 

 having considered it, with a good deal of doubt, a variety of U. calceo- 

 lus (nobis). Like that shell it has a very imperfectly formed lateral 

 tooth ; in most individuals it cannot be perceived. In comparison 

 with the calceolus, it is more triangular and flattened, and the undula- 

 tions of the beaks are unbroken. The beaks are of a darker colour, 

 and the anterior lobe of the cardinal teeth seems to be larger in this, 

 while in the other the posterior seems to be the larger. The deltoi- 

 dea is also a smaller shdl. 



