96 NEW UNIONID.E OF THE UNITED STATES. 



Unio anaticulus. pi. 13, fig. 240. 



Testa Irevi, obliqua, ad umbones valde tumida, antic6 truncata, posticfe obtuse angulata, valdg inaquilaterali; 

 valvulis crassiuseulis, antice crassioribus ; natibus elevatis, crassis, incurvis, fere terminalibus ; epidermide 

 castanea, vittata, obsolete radiata; dentibus cardinalibus subcrassis, subpyramidatis cvenulatisciue ; later- 

 alibus crassis, obliquis subrectisque ; margarita argentea et iridesoente. 



Shell smooth, oblique, very much swollen at the beaks, truncate before, obtusely 

 angular behind, very inequilateral ; valves somewhat thick, thicker before ; beaks 

 raised, thick, incurved, nearly terminal; epidermis chestnut color, banded, obscurely 

 radiate ; cardinal teeth rather thick, subpyramidal and crenulate ; lateral teeth thick, 

 oblique and nearly straight ; nacre silver white and iridescent. 

 Proc. Acad. Nat. Soi. 18G1, p. 40. 



Eab. — Near Columbus, Mississippi. Wm. Spillman, M. D. 



My cabinet, and cabinet of Dr. Spillman. 

 Diam. -7, Length 1. Breadth 1-4 inch. 



Shell smooth, oblique, much swollen, at the beaks, truncate before, obtusely angular 

 behind, very inequilateral ; substance of the shell somewhat thick, thicker before ; 

 beaks raised, thick, incurved and nearly terminal;, ligament rather short, somewhat 

 thick and brown; epidermis chestnut color inclining to yellow, transversely banded, 

 with a few obscure rays, and with three or four distant lines of growth ; unibonial 

 slope slightly raised and flattish ; posterior slope rather narrow, elongate cordate, 

 with two obscure impressed lines in each valve; cardinal teeth somewhat thick, sub- 

 pyramidal and crenulate ; lateral teeth thick, oblique and nearly straight ; anterior 

 cicatrices distinct, rather small and deeply impressed; posterior cicatrices distinct, 

 rather small and well impressed ; dorsal cicatrices placed on the upper side of the 

 cavity of the beak at the end of the cardinal tooth ; cavity of the shell rather shallow 

 and rounded ; cavity of the beaks very shallow and oljtusely angular ; nacre silver 

 white and iridescent. 



Remarlcs. — This species is closely allied to curtus (nobis) . They are so nearly alike 

 that at first I considered it only a variety. They may, however, be distinguished by 

 the color, the bands and slight difference of form. Of seven specimens before me 

 none have the dark green color which pervades the umbones of curtus. In the 

 bands, which are strongly marked at the lines of growth in anaticulus, they difier 

 entirely. Curtus is a somewhat larger species, and more tumid, heavier, is not 

 so oblique, and has more depression before the umbonial slope. The rays of ctJia^i- 

 culus are more distinct on the young, and are interrupted by the transverse bands, none 

 of them extending to the margin. The color of the epidermis is very uniform except 

 on a single specimen, which inclines to olive yellow, and is almost rayless. It re- 

 minds one also of mecUiis (nobis) on one side, and decisus (nobis) on the other, but is 



