UNITEU STATES. 77 



a young individual, but I cannot place it with any doso.rihed species. The nacre is 

 slightly purple in the cavity of the beaks. The undulations of the beaks are uncom- 

 monly regular and very beautiful. In this specimen there are seven on each beak, 

 all regulai'ly succeeding each other and forming an acute angle in the middle. 



UnIO FNTKRCEnENS. PI. IT), fig. -")7. 



Testa laevi, elliptica, subinflata, valde intcquilaterali, postice subangulata ; valvulis subcrassis ; natibus 

 prominulis ; epidermide tenebroso-fuscil ; postice radiata, antice subsulcata ; dentibus cardinalibus 

 parvis, angulatis, in utroquo valvnlo duplicibus ; latcralibus longis, lamellatis subrectisquc ; margarita 

 purpurea et iridescente. 



Shell smooth, elliptical, somewhat inflated, very inequilateral, subangular behind ; 



valves somewhat thick ; beaks a little prominent, epidermis dark brown, radiated 



behind and slightly furrowed before ; cardinal teeth small, angular, double in both 



valves ; lateral teeth long, laniellar and nearly straight ; nacre purple and iridescent. 



Proo. Acad. Nat. Sci. 1857, p. 32. 



Ilah. — Streams near Columbus, Georgia. Bishop Elliott. 



My cabinet and cabinet of Bishop Elliott. 

 Diam. -8, Length 11, Breadth 19, inches. 



Shell smooth, elliptical, somewhat inflated, very inequilateral, obtusely angular 

 behind and rounded before ; substance of the shell somewhat thick, thicker before ; 

 beaks a little prominent, ligament rather long and thin ; epidermis dark brown, 

 obscurely radiated behind and slightly furrowed before with rather distant marks of 

 growth; umbonial slope slightly elevated and rounded ; cardinal teeth small, angular, 

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

 anterior cicatrices distinct and deeply impressed ; posterior cicatrices confluent ; dorsal 

 cicatrices placed in the centre of the cavity of the beaks ; cavity of the shell rather 

 shallow ; cavity of the beaks very shallow and subangular : nacre purple and 

 iridescent. 



Soft Parts. — A male. BrancMcv large, rounded below, inner ones much the larger, 

 closed the whole length of abdominal sack. Palpi very large, thick, suboval, united 

 more than halfway down the posterior edges. Mantle thickened and double along the 

 edge, colored below the branchial opening where there arc small somewhat distant 

 papillae. Brancliial openinrj large, with numerous small brownish papilhe on the inner 

 edges. Anal opening rather large, with minute papilla^ on the anterior edges. Super- 

 anal opening rather small, inner edges colored, united ])elow for some distance. Color 

 of the mass whitish. 



Remarlcs. — A single specimen, a male, in alcohol and several dry ones were received 

 from Bishop Elliott. It belongs to i\ic fallax group and inclines to suhellipfsis (nobis). 

 It differs from the latter in color of the nacre and in the rays. It is a more com- 



I'd 



