7G NEW UNIONIDJE OF THE UNITED STATES. 



Embryonic shell elongato-pouch-shapc, nearly that of the U. multiradiatus, (nobis) ; 

 color clear white. 



Remarks. — I have three specimens before me. The largest one nearly two and a 

 half by one and a half inches, has been in my possession about thirty years. It was 

 sent to me, with many fine shells, by my deceased friend Judge Tait, of Claiborne, 

 Ala. It so closely resembles, in outline, young specimens of jpurpiwatus, Lam., that it 

 was jflaced with them with a mark of doubt. Since then, until recently, I have never 

 seen .another specimen of it. Dr. Showalter, of Unionville, Ala., among other species 

 in alcohol, has sent me two young individuals, the larger of which fortunately is a 

 female with the embryonic form well developed in the branchial uterus. This at 

 once settled the difficulty, the form being pouch-shape while that of purpuratus is wedge- 

 shape. Purpuratus is a large, thick, deep purple species, usually much inflated, while 

 dolosus is a thin, smaller species, the three species before me, neither of which is pro- 

 bably Ml grown, being respectively nearly two and a half, two and one inch wide. It 

 differs also in being white, with a very slight tint of purple about the teeth. The largest 

 specimen is abnormal in the lateral teeth, being single in both valves. The rays are 

 scarcely to be observed on the oldest and youngest specimens, while they are obser- 

 vable on the middle-aged one. The beaks are eroded in each of them, but there re- 

 mains enough in one to show that there are small undulations on the tips. It is very 

 closely allied to permiscens (nobis), but is not so much inflated, and has stronger teeth. 



Unio negatus. PL 9, fig. 225. 



Testa sulcata, subtriangulavi, compressa, ad latere planulata, postice obtuse biangulata, antice rotunda, 

 subsequilaterali ; valvulis subcrassis, antice crassioribus ; natibus subprotninentibus, acuminatis, ad 

 apices corrugatis; epidertnide refuo-fusea, obsolete radiata; dentibus cardinalibus subgrandibus, 

 striatis crenulatisque ; lateralibus subcrassis, sublongis subreetisque ; margarita vel alba vel rosacea 

 et iridescente. 



Shell sulcate, subtriangular, compressed, flattened at the sides, obtusely biangular 

 behind, rounded before, nearly equilateral ; valves rather thick, thicker before ; beaks 

 somewhat prominent, acuminate, corrugate at the tips; epidermis reddish brown, 

 obscurely radiate ; cardinal teeth rather large, striate and crenulate ; lateral teeth 

 rather thick, rather long and nearly straight; nacre white or rose colored and 

 iridescent. 



Proc. Acad. Nat. Sci. 1861, p. 59. 



Hob— Big Prairie Creek, Ala., E. K. Showalter, M. D. ; and Columbus, Miss., W. 

 Spillman, M. D. 



My cabinet and cabinets of Drs. Showalter and Spillman. 

 Diam. 1, Length 1*8, Breadth 2-7 inches. 



Shell sulcate, subtriangular, compressed, flattened at the side, obtusely biangular 



