CHIEFLY OF THE UNITED STATES. 305 



Unio genuinus. pi. 46, fig. 117. 



Testa la3vi, elliptiea, subinflata, inajquilaterali, postice subbiangulata, antiee rotundata ; valvulis sub- 

 tenuibus, antiee crassioribus ; natibus subprominentibus ; epidermide luteola, valde radiata ' 

 dentibus cardinalibus erectis, pyramidatis ; lateralibus longis, subcurvis lamellatisque ; margarita 

 alba et irideseente. 



Shell smooth, elliptical, somewhat inflated, inequilateral, subbiangular behind, 

 rounded before ; valves rather thin, thicker before ; beaks somewhat prominent ; 

 epidermis yellowish, very much radiated; cardinal teeth erect, pyramidal; lateral 

 teeth long, somewhat curved and lamellar ; nacre white and iridescent. 

 Proc. Acad. Nat. Sci. 1868, p. 161. 



Hah.— BisseVs Pond, Charlotte, N. C, C. M. Wheatley. 



My cabinet and cabinet of Mr. "Wheatley. 

 Diam. -8, Length 1-2, Breadth 2 inches. 



Shell smooth, elliptical, somewhat inflated, inequilateral, subbiangular behind, 

 rounded before ; substance of the shell rather thin, thicker before ; beaks somewhat 

 prominent; ligament rather long, chestnut-brown color; epidermis yellowish, with 

 ■numerous green capillary rays on the posterior half, with distant marks of growth ; 

 umbonial slope rounded ; posterior slope narrow elliptical and slightly carinate ; 

 cardinal teeth erect, pyramidal and double in the right and disposed to be treble in 

 the left valve ; lateral teeth long, somewhat curved and lamellar; anterior cicatrices 

 confluent, rather small and moderately impressed ; posterior cicatrices confluent and 

 slightly impressed ; dorsal cicatrices placed over the centre of the cavity of the 

 beaks ; cavity of the shell rather deep and wide ; cavity of the beaks rather deep 

 and rounded ; nacre white and iridescent. 



EemarJcs. — Mr. Wheatley submitted three specimens of this shell to me. It is so 

 closely allied to intercedens awAfallax (nobis) that I was not disposed to consider it 

 different, until I gave it a complete examination and comparison. It is rather more 

 compressed than either, and is more enlarged over the umbonial slope, where the 

 rays are also more capillary. In all the three specimens the nacre is Avhite, while in 

 the other two species mentioned above it is usually salmon and purple. The beaks 

 are too much eroded to distinguish the undulations. 



Unio FAssiNANS. PI. 47, fig. 118. 



Testa Isevi, elliptiea, subcompressa, intequilaterali, postice obtuse angulata, antiee rotundata ; valvulis 

 crassiusculis, antiee crassioribus ; natibus subprominentibus ; epidermide tenebroso-rufo-fusca, 

 eradiata; dentibus cardinalibus crassiusculis, compressis, obliquis; lateralibus sublongis, crassis, 

 obliquis corrugatisque ; margarita salmonis colore tiucta, splendens et irideseente. 



Shell smooth, elliptical, subcompressed, inequilateral, obtusely angular behind, 

 rounded before; valves somewhat thick, thicker before; beaks somewhat prominent; 

 epidermis dark reddish-brown, without rays; cardinal teeth somewhat thick, 



