UNITED STATES AND ARCTIC AMERICA. 207 



Bab. — Near Hot Springs, Arkansas, Byrd Powell, M. D. 



Cabinet of the Smithsonian Institution. 

 Diarn. -7, Length 1-1, Breadth 1'5 inch. 



Shell smooth, ovately oblique, compressed behind, inequilateral, obtusely biangular 

 behind and round before ; substance cf the shell somewhat thick, thicker before ; 

 beaks somewhat raised and approaching to medial ; ligament rather short ; epidermis 

 yellowish, inclining to greenish, with rather close marks of growth ; umbonial slope 

 slightly raised ; posterior slope narrow elliptical, cardinal teeth small, striate, crenu- 

 late, double in the left and disposed to be treble in the right valve ; lateral teeth 

 rather long, nearly straight, and thickened towards the end ; anterior cicatrices dis- 

 tinct and well impressed ; posterior cicatrices distinct and moderately well impressed ; 

 dorsal cicatrices in a row on the upper side of the cavity of the beaks ; cavity of the 

 shell shallow and wide ; cavity of the beaks shallow and obtusely angular ; nacre 

 pearly white and very iridescent. 



Remarks. — A single specimen of this species was sent by Dr. Powell, and it is too 

 imperfect to give the character of the undulations of the beaks. In outline it is nearest 

 to modieellus, (nobis,) but it is a larger species and more compressed. It is nearly of 

 the size of Ravenellianus, (nobis,) and is compressed like it, but it is not so oblique 

 and the epidermis is more yellow. 



Unio speciosus. PI. 31, fig. 276. 



Testa ornnind tuberculata, fere granulata, quadrangulari, valde eonrpressa, ad latere planulata, sub- 

 aequilaterali, postice subbiangulata et eraarginata, antiee rotundata ; valvulis subcrassis, antiee 

 paulisper crassioribus ; natibus subelevatis, ad apices actmiinatis et elegantissirne perundulatis ; 

 epidermide viridi-lutea, substriata, vel obsolete radiata vel eradiata, submicanti ; dentibus cardi- 

 nalibus subgrandibus, compressis, obliquis, erectis, striatis, in utroque valvulo duplicibus ; laterali- 

 bus rectis, sublongis obliquisque ; margarita argentea et irideseente. ' 



Shell covered with tubercles, almost granular, quadrangular, very much com- 

 pressed, flattened at the sides, nearly equilateral, subbiangular and emar- 

 ginate behind, rounded before ; valves rather thick, slightly thicker before ; beaks 

 somewhat elevated, pointed and beautifully undulate at the tips ; epidermis greenish 

 yellow, substriate, obscurely radiate or without rays, somewhat shining; cardinal 

 teeth rather large, compressed, oblique, erect, striate, double in both valves ; 

 lateral teeth straight, rather long and oblique ; nacre silver white and iridescent. 

 Proc. Acad. Nat. Sci., 1862, p. 168. 

 Hob. — Colorado River, near Lagrange, Texas, Prof. Forshey ; and Leon County, 

 Texas, Lieut. E. P. Beale. 



My cabinet and cabinet of Prof. Forshey and Smithsonian Institution. 

 Diam. -7, Length 1-5, Breadth 1-2 inch. 



Shell covered over with small tubercles, almost granular, quadrangular, very much 



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