206 DESCRIPTION OF 



rather short and thin; epidermis dark brown, obscurely rayed; umbonial slope 

 rounded; cardinal teeth small, erect, pointed, double in the left and single in 

 the right valve; lateral teeth long, nearly straight, separated from the cardinal 

 tooth; anterior cicatrices distinct; posterior cicatrices confluent; dorsal cica- 

 trices placed directly in the cavity of the beaks; cavity of the shell rather deep; 

 cavity of the beak shallow and angular; nacre of a very splendid copper-colour, 

 whitish on the anterior basal margin, dark in the cavity and posterior part, 

 beautifully iridescent. 



Remarks. — The bright and splendid hue of the nacre of this species is supe- 

 rior to any other which has come under my notice. In outline it is closely 

 allied to U. ohscurus (nobis,) but its fine nacre easily distinguishes it. In young 

 specimens may be observed indistinct small rays over the posterior part of the 

 disk. Two of the specimens before me are enlarged at the posterior basal 

 margin, indicating their being females. 



Unio lineatus. Plate 12, Fig. 20. 



Testa elUpticd, inflata; valvulis tenuihus; natibus subprominentibus, ad apices undulatis; epidermide 

 luted, radiatd, politd; dentibus cardinalibus parvis, lamellatis; lateralibus parvis, subcurvisque ; mar- 

 garitd salmonis colore tinctd et iridescente. 



Shell elliptical, inflated; valves thin; beaks rather prominent, undulate at the tip; epidermis yellow, radi- 

 ated, polished; cardinal teeth small, lamellar; lateral teeth small and somewhat curved; nacre salmon- 

 coloured and iridescent. 



Hab. Chattahoochee River, Columbus, Georgia. Dr. Boykin. 



My Cabinet. 

 Diam. .6, Length .9, Breadth 1.4 inches. 



Shell elliptical, inflated, with distinct linear rays over the whole disk except 

 on the posterior slope; substance of the shell thin ; beaks rather prominent, un- 

 dulate at the tip; ligament short and rather thick; epidermis yellow and finely 

 polished; cardinal teeth small, compressed, disposed to be double in both valves; 

 lateral teeth small and somewhat curved; anterior cicatrices distinct; posterior 

 cicatrices confluent; dorsal cicatrices on the plate between the cardinal and 

 lateral teeth; cavity of the shell large; cavity of the beaks rather deep and an- 

 gular; nacre salmon-coloured and iridescent. 



