56 NEW UNIONIDiE OF THE UNITED STATES. 



teeth small, rather compressed, crenulate, double in both valves; lateral teeth short, 

 rather thick and straight; nacre white or saffron and iridescent. 

 Proc. Acad. Nat. Sci. 1857, p. 8G. 



Hab. — Roanoke River, Weldon, N. C. Prof. Emmons. 



My cabinet and cabinet of Prof. Emmons. 

 Diam. -6, Length 1, Breadth 1-5 inch. 



Shell smooth, triangular, somewhat inflated, nearly equilateral, angular behind and 

 round before; substance of the shell rather thick, thicker before; beaks elevated, 

 acuminate, rugosely undulate at the tips; ligament very short, somewhat thick and 

 light brown; epidermis chestnut brown, minutely striate, obscurely rayed and with 

 very distant marks of growth; umbonial slope slightly and obtusely angular; pos- 

 terior slope rather compressed, slightly raised, with two slightly impressed lines from 

 the beaks to the margin ; cardinal teeth small, rather compressed, very much crenu- 

 late and double in both valves; lateral teeth short, rather thick and straight; anterior 

 cicatrices distinct, small and well impressed ; posterior cicatrices confluent, small and 

 slightly impressed ; dorsal cicatrices placed on the under side of the plate posterior to 

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

 rather deep and angular; nacre white or saffron and iridescent. 



Remarks. — Several specimens are before me. In outline it is near to rubiginosus, 

 (nobis,) and belongs to the group of which that is the type ; but it is a smaller species, 

 is rather more inflated, and has higher beaks. In some specimens the lateral teeth 

 are disposed to turn up at the posterior end. 



Unio Emmonsii. PI. 2, fig. 203. 



Testa laevi, transversa, subcompressa, valde incequilaterali, postice subbiangulata, ad latere planulata; valvu- 

 lis subcrassis; natibas vix prominulis, ad apices undulatis, epidermide tenebroso-fusca, radiata, nitida ; 

 dentibus cardinalibus subgrandibus, compressis, crenulatis, in utroque valvule- duplicibus; lateralibus 

 pralongis, lamellatis rcctisque ; margarita alba et iridescente. 



Shell smooth, transverse, rather compressed, very inequilateral, subbiangular be- 

 hind, flattened at the sides ; valves thick ; beaks scarcely prominent, undulate at the 

 tips; epidermis dark brown, rayed, shining; cardinal teeth rather large, compressed, 

 crenulate and double in both valves ; lateral teeth very long, lamellar and straight ; 



nacre white and iridescent. 



Proc. Acad. Nat. Sci. 1857, p. 8.6. 



Hob. — Roanoke River, Weldon, N. C. Prof. E. Emmons. 



My cabinet and cabinet of Prof. Emmons. 

 Diam. 1, Length 1/7, Breadth 4-4 inches. 



Shell smooth, transverse, rather compressed, very inequilateral, subbiangular be- 

 hind, flattened at the sides ; substance of the shell thick ; beaks scarcely prominent, 



