106 NEW UNIONID^ OF THE UNITED STATES. 



not quite so rotund, nor is it nearly so thick. It is also a much smaller species, and 

 differs entirely in the form of the cardinal teeth, which, in the rotundatus, are very 

 much divided. In the Ghiclcasawhensis the cardinal tooth in the right valve is dis- 

 posed to be duplicate, as that of the left valve is entirely. 



Unio permiscens. pi. 17, fig. 251. 



Testa IciBvi, obovata, inflata, postice latd rotunda, valde inaequilaterali ; valvulis tenuibus ; natibus prominulis ; 

 epidermide tenebroso-fusca, nigricante, obsolete perradiata, nitida; dentibus cardinalibus parvulis, 

 compressis, obliquis ; lateralibus prtelongis, lamellatis subcurvisque ; margarita creruleo-alba et valde 

 iridesceiite. 



Shell smooth, obovate, inflated, broadly rounded behind, very inequilateral; valves 

 thin ; beaks a little prominent ; epidermis dark brown, inclining to black, obscurely 

 radiated all over, shining; cardinal teeth small, compressed, oblique; lateral teeth 

 very long, lamellar and somewhat curved ; nacre bluish white and very iridescent. 

 Proc. Acad. Nat. Sci. 1859, p. 112. 



Hah. — Tombigbee River, Columbus, Mississippi. Wm. Spillman, M. D. 



My cabinet, and cabinet of Dr. Spillman. 

 Diam. -7, Length 1-4, Breadth 2-1 inches. 



Shell smooth, obovate, inflated, broadly rounded behind and obliquely rounded 

 before, very inequilateral; substance of the shell thin; beaks a little prominent; 

 ligament rather long, thin and dark brown ; epidermis dark brown, almost black, 

 obscurely radiated all over, and with distant marks of growth; umbonial slope raised 

 and I'ounded; posterior slope blackish and almost raised into a wing; cardinal teeth 

 small, compressed, oblique and scarcely double in the left valve ; lateral teeth very 

 long, lamellar and somewhat curved; anterior cicatrices rather large and distinct; 

 posterior cicatrices confluent ; dorsal cicatrices in a row across the centre of the cavity 

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

 shallow and rounded ; nacre bluish white and iridescent. 



Soft parts. — A male. Branchiae thin, rather large, inner ones much the larger, rounded 

 below, free only at the extreme point of abdominal sack. Palpi very large, nearly 

 semi-circular, rather thin, united one-third down the posterior edges. Mantle thin, 

 with rather a broad bordei', crenulate below the branchial opening. Brancldal open- 

 ing rather small, with rather large brownish papillae. Anal opening rather large, with 

 numerous small, brownish papillse. Anus with small crenulations on the rim and 

 pointed at the lower end. Super-anal opening large, colored within and united below. 

 Color of the mass whitish. 



Remarlcs. — The above description is made from two specimens, one only being re- 

 ceived in alcohol with the soft j^arts. It is very much like U.purpuratus, Lam., in out- 

 line, and at first I supposed it might be immature ; but it is a very much thinner species, 



