\EW UNIOXID.K OF THE LXITKD STATES. lUo 



• 



received from Dr. Spillmiui witli the soft parts. The beaks of ijutli 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 Brumhyaims (nobis), but cannot be confounded with either. 

 The epidermis of Brumhi/anii-s is nearly or quite black ; mix is dark olive, and has 

 higher unibones. The nacre of cimiamomicus 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 (Jhickasawiiensis. pi. 16, fig. 250. 



Testa hiivi, subrotuiiJa, subcompressa, sublenticulari, inffiquilaterali, postice obtuse angulata, antice rotun- 

 da ; valvulis crassiusculis, antice paulisper crassioribus ; natibus prominulis ; epidermidc tenebroso- 

 fusca, eradiata, escellismo striata; dentibus cardinalibus parviusculis, pyramidatis, corrugatis creniiLi- 

 tisque ; lateralibus brevibus, subvalidis subcurvisque ; margarita rosacea ct valdo irideseente. 



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

 ano-ular 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, coi'rugate and crenulate; lateral teeth short, 

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

 Proc. Acad. Nat. Sci. 1861, p. 80. 



5-a/;._Chickasawha River, Mississippi. Wm. Spillman, M. D. 



My cabinet and cabinet of Dr. Spillman. 

 Diam. -G, Length 1-1, Breadth l-o 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. 



BemarJcs. — 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 



