276 MR. CONRAD'S DESCRIPTIONS OF 



U, ORATUS. PI. 37, fig. 6.— Widely elliptical, ventricose, gaping at both ends; posterior gape wide; 

 anterior extremity rather acutely rounded ; posterior margin sinuous, extremity subangular ; basal 

 margin forming a nearly regular curve ; summits prominent ; umbo and beak eroded ; epidermis 

 ochraceous, polished ; cardinal teeth compressed, oblique; lateral teeth straight; within white, much 

 stained with waxen yellow. 



Proceed. Acad. Nat. Sc, Vol. iv., p. 153. 



Inhabits Flint River, Georgia. 



This shell has the polished epidermis of U. canosus, but is without a ray. It is 

 longer in proportion than that species with very different cardinal teeth, which are 

 much nearer parallel with the margin above. 



U. coNTRARius. PI. 37, fig. 7. — Elliptical, moderately thick ; valves somewhat flattened or plano-convex ; 

 umbo and beak not prominent, much eroded ; umbonal slope acutely rounded ; posterior margin 

 straight above, truncated, direct ; epidermis deep ochraceous, with linear radiating wrinkles, and 

 obscurely rayed about the umbo ; within pale liesh-color, stained with waxen yellow ; cardinal teeth 

 direct, thick, sulcated, not very prominent ; lateral teeth reversed, or the double tooth in the right 

 valve. 



Proceed. Acad. Nat, Sc, Vol. iv., p. 153. 

 Inhabits Ogeechee River, Georgia. 



U. NUCLEOPsis. PL 37, fig. 8. — Obtusely subovate, slightly oblique, thick, not ventricose ; umbonal slope 

 rounded ; posterior slope with a few obscure plaits ; posterior margin subtruncated ; basal margin 

 slightly tumid near the middle ; epidermis ochraceous, with a series of green spots along the umbonal 

 slope ; posterior slope obsoletely striated ; within bluish white ; cardinal teeth thick, direct, single in 

 the right valve. 



Proceed. Acad. Nat. Sc, Vol. iv., p. 154. 



Inhabits Etowah River, Georgia. 



U. LiMATULus. PI. 37, fig. 9. — Subelliptical, convex ; posterior side somewhat pointed ; umbonal slope 

 angular ; posterior slope subcarinated in the middle ; posterior margin obliquely truncated ; extremity 

 truncated, direct ; basal margin regularly rounded ; beaks not prominent, eroded ; epidermis highly 

 polished, dark brown and ochraceous, obscurely rayed ; within flesh color or pale salmon ; cardinal 

 teeth oblique, compressed, double in each valve ; lateral teeth long, slightly curved. 

 Proceed. Acad. Nat. Sc, Vol. iv., p. 154. 



Inhabits Savannah River, 



U. PERPLicATUs. PL 38, fig. 2. — Obtusely subovate, very ventricose ; rather thick, with about twelve 

 oblique, profound plicae, those behind the umbo recurved ; ligament margin greatly elevated ; posterior 

 superior margin slightly concave, oblique, extremity truncated ; epidermis blackish-brown, apex 

 eroded ; within tinged with purple ; cardinal teeth direct, prominent, sulcated. 

 Proceed. Acad. Nat. Sc, VoL i., p. 19. May 1841. 



U. ATR0C0STATU3. — Lea. Trans. Amer. Philos. Soc. (N. S.) Vol. x., pL 2, fig. 5, 1847. 

 Inhabits with U. nodiferus, near Jackson, Louisiana. 



