CHIEFLY OF THE UNITED STATES. 19 



Shell smooth, elliptical, somewhat inflated, very inequilateral ; substance of the 

 shell rather thin, slightly thiclver before; beaks somewhat prominent; ligament 

 small, thin and light brown ; epidermis yellowish green, very bright, nearly covered 

 with rays, with rather distant marks of growth ; umbonial slope raised and rounded ; 

 posterior slope rather broad, elliptical, with numerous green rays, slightly raised into 

 a carina ; cardinal teeth small, compressed, crenulate, double in both valves ; lateral 

 teeth long, lamellar and nearly straight ; anterior cicatrices distinct, large and well 

 impressed ; posterior cicatrices confluent, large and slightly impressed ; dorsal cica- 

 trices placed nearly in the centre of the cavity of the beaks ; cavity of the shell 

 somewhat deep and wide ; cavity of the beaks very shallow and rounded ; nacre 

 bluish white and very iridescent. 



Remarks. — Three specimens and an odd valve were all I received from Dr. 

 Emmons. One only is adult. The epidermis is remarkable for its polished, bright 

 surface, presenting as it does the appearance of being varnished. In this respect it is 

 very like to micans (nobis), and it has a resemblance in the outline, but is very dif- 

 ferent in the umbonial slope, which in perlucens is swollen, while in micans it is 

 flattened. It is also less pointed in the posterior margin and is a thinner shell. 



Unio cistell^formis. pi. 6, fig. 17. 



Testa laevi, oblonga, valde inflata, ad latere planulata, insequilaterali, postice obtuse biangulata, antice 

 rotunda; valvulis crassiusculis ; natibus prominulis; epidermide fusco-nigricante, eradiata; dentibus 

 cardinalibus parvis, tuberculatis, in utroque valvule duplicibus ; lateralibus sublongis, lamellatis sub- 

 rectisque; margarita alba et iridescente. 



Shell smooth, oblong, very much inflated, flattened at the side, inequilateral, ob- 

 tusely biangular behind, rounded before ; valves somewhat thick ; beaks somewhat 

 prominent ; epidermis blackish brown, without rays ; cardinal teeth small, tuberculate, 

 double in both valves; lateral teeth rather long, lamellar and nearly straight; nacre 

 white and iridescent. 



Proc. Acad. Nat. Sci., 1863, p. 192. 



Eah. — Neuse River, near Raleigh, North Carolina, E. Emmons, M. D. 



My cabinet and cabinet of Dr. Emmons. 

 Diam. -9, Length 1, Breadth 1-8 inches. 



Shell smooth, oblong, very much inflated, flattened at the side, inequilateral, ob- 

 tusely angular behind, rounded before ; substance of the shell somewhat thick ; beaks 

 somewhat prominent ; ligament rather short and dark brown ; epidermis dark bi'own, 

 without rays, with rather close marks of growth ; umbonial slojie swollen and rounded ; 

 posterior slope broad, flattened, scarcely carinate ; cardinal teeth small, tuberculate, 

 double in both valves ; lateral teeth rather long, lamellar and nearly straight ; anterior 



