NEW UNIONIDtE OF THE UNITED STATES. 101 



received from Dr. Spillman with the soft parts. The beaks of both were eroded, and 

 therefore the character of the tips could not be described. This species is remarka- 

 ble for its fine cinnamon-colored epidermis, in which it is peculiar. In outline, it is 

 allied to mix (nobis) and Brumbyanus (nobis), but cannot be confounded with either. 

 The epidermis of Brumbyanus is nearly or quite black; mix is dark olive,. and has 

 higher umbones. The nacre of cinnamomicus is remarkable. The anterior two-thirds 

 of the valve is thickened, and, in one of the specimens, a dead-cream white, the pos- 

 terior third being thin and beautifully iridescent. The other specimen is very slightly 

 tinted with a blush color. 



Unio Chickasawhensis. PI. 16, fig. 250. 



Testa IfBvi, subrotunda, subcompressa, sublenticulari, inaequilaterali, postice obtuse angulata, antice rotun- 

 da ; valvulis crassiusculis, antice paulisper crassioribus ; natibus prominuiis; epidermide tenebroso- 

 fuscix, eradiata, excellisiue striata; dentibus eardinalibus parviuseulis, pyramidatis, corrugatis erenula- 

 tisque; lateralibus brevibus, subvalidis subeurvisque; margarita rosacea et valde iridescente. 



Shell smooth, subrotund, rather compressed, sublenticular, inequilateral, obtusely 

 angular behind, round before ; valves somewhat thick, slightly thicker before ; beaks 

 slightly prominent ; epidermis dark brown, without rays and very closely striate ; 

 cardinal teeth rather small, pyramidal, corrugate and crenulate ; lateral teeth short, 

 rather stout and somewhat curved ; nacre rose color and very iridescent. 

 Proc. Acad. Nat. Sci. 1861, p. 39. 



Hab. — Chickasawha River, Mississippi. Wm. Spillman, M. D. 



My cabinet and cabinet of Dr. Spillman. 

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



Shell smooth, subrotund, rather compressed, sublenticular, inequilateral, obtusely 

 angular behind and round before ; substance of the shell somewhat thick, slightly 

 thicker before ; beaks slightly prominent ; ligament short, thick and dark brown ; 

 epidermis very dark brown, without rays, very minutely striate and with rather dis- 

 tant marks of growth; umbonial slope slightly raised and obtusely angular; posterior 

 slope narrow, elliptical, subcarinate, with two indistinct, impressed lines on each 

 valve ; cardinal teeth rather small, pyramidal, corrugate and crenulate ; lateral teeth 

 short, rather stout and slightly curved ; anterior cicatrices distinct, rather small 

 and well impressed ; lateral cicatrices confluent, rather small and well impressed ; 

 dorsal cicatrices placed on the plate -within the cavity of the beaks; cavity of the 

 shell rather shallow and wide; cavity of the beaks shallow and subangular; nacre 

 slightly rose-color, reddish along the margin and very iridescent. 



Remarks. — A single specimen of this species was received from Dr. Spillman. The 

 beaks being imperfect, it is impossible to know what may be the character of the un- 

 dulations of the tips. In outline, it is nearly allied to rotundatus, Lam., but it is 



26 



