DESCRIPTION OF FIFTY-TWO SPECIES OP UNIONIDiE. 11 



under the marks of growth before the umbonial slope. The epidermis is disposed 

 to be TOugh and slightly scaly, like plenus (nobis), and it has a general resemblance 

 to that species, but it is rounded and has not the flattened side of that species. 

 Neither of the specimens is perfect enough in the beaks to display undulations. 

 I owe to the kindness of Dr. Lewis in being able to cite my cabinet for a specimen. 



ITnio Tuscumbiensis. pi. 3, fig. 7. 



Testa Isevi, triangular!, tumida, ad latere pl^nulata, insequilaterali, antice subtruncata, postice obtuse 

 angulata; valvulis crassis, antice crassioribus ; natibus elevatis, subretusis ; epidermide luteo- 

 oliva, perradiata; dentibas cardinalibus parviusculis, subcompressis crenulatisque ; lateralibus 

 Curtis, subcrassis subrectisque ; margarita argentea et iridescente. 



Shell smooth, triangular, swollen, flattened at the sides, inequilateral, subtrun- 

 cate before, obtusely angular behind ; valves thick, thicker before ; beaks raised, 

 somewhat retuse ; epidermis yellowish olive, very much rayed ; cardinal teeth 

 rather small, somewhat compressed and crenulate; lateral teeth short, somewhat 

 thick and straight ; nacre silver white and iridescent. 

 Proc. Acad. Nat. Sci., ISTl, p. 190. 



Hah. — Tuscumbia, Ala., L. B. Thornton, Esq. • Holston Kiver, E. Tenn., Dr. 

 Edgar. 



My cabinet. 

 Diam. -9, Length 1-3, Breadth 1-6 inch. 



Shell smooth, triangular, inflated, flattened at the sides, inequilateral, subtrun- 

 cate before and obtusely angular behind; substance of the shell thick, thicker 

 before ; beaks prominent and somewhat retuse ; ligament very short, reddish 

 brown ; epidermis yellowish olive, rayed nearly over the whole disk, with rather 

 close marks of growth; umbonial slope raised and obtusely angular; posterior slope 

 flattened and cordate ; cardinal teeth rather small, somewhat compressed, crenulate, 

 double in the left and treble in the right valve ; lateral teeth short, somewhat 

 thick and nearly straight; anterior cicatrices distinct, small and deeply impressed; 

 posterior cicatrices distinct and well impressed ; dorsal cicatrices placed on the 

 under side of the plate within the cavity of the beaks ; cavity of the shell rather 

 deep and rounded; cavity of the beaks rather deep and obtusely angular; nacre 

 very white and iridescent. 



Remarks. — Dr. Edgar more than twenty years since sent me a single specimen 



of this species, which is so closely allied to cuneolus (nobis) that I placed it among 



that species as a variety. Subsequently Mr. Thornton sent me three of different 



•ages, and I have no longer any doubt but that they are distinct. It may be distin- 



