LUG NEW UN10NID/TC OF THE UNITED STATES. 



and was charged with embryos and ova — there were no ova in the ovarium. Branchiae 

 large, somewhat thick, rounded below, inner ones much the larger, free one-third the 

 length of abdominal sack. Palpi long, oblique, subelliptical, united two-thirds down 

 the posterior edges. Mantle rather thin, with a broad, thickened border. Branchial 

 opening large, blackish within, with numerous, thickly-set, reddish brown papilla?. 

 Anal opening large, blackish within, crenulate on the edges. Anus large and crenulate 

 on the edge. Super-anal opening large, with a dark line on the inner edge, and 

 united below; color of the mass whitish. 



Embryonic shell light brown, subtriangular, has imperfect hooks. 



Remarks. — I have several specimens of this fine species before me. It is very 

 different from any heretofore described. In its great inflation on the umbonial slope, 

 it reminds one of Anodonta gibbosa, Say. The cardinal teeth are like those of 

 M. Elliottii (nobis). The undulations of the beaks consist of four or five, are sub- 

 concentric and well-defined. The margin is wide and reddish. In some specimens 

 the color of the epidermis is, in transverse bands, of lighter and darker brown, the 

 young being well rayed ; the figure is from a male specimen. I have great pleasure 

 in naming this fine species after Wm. Spillman, M. D., who has done so much to 

 elucidate the natural history and geology of his State. 



Margaritana elliptica. PI. 18, fig. 254. 



Testa loevi, elliptica, subinflata, subasquilaterali, postice obtuse angulata; valvulis tenuibus; natibus sub- 

 prominentibus, ad apices subconeentrice undulatis; epidermide lutco-virente, glabra, nitida, perndiata; 

 dentibus cardinalibus parvis, cotnpvessis, in utroque valvule singulis ; rnargarita cEeruleo-alba et 

 iridescente. 



Shell smooth, elliptical, somewhat inflated, nearly equilateral, obtusely angular 

 behind ; valves thin ; beaks somewhat prominent, with subconcentric undulations at 

 the tips ; epidermis yellowish green, smooth, shining, very much radiated ; cardinal 

 teeth small, compressed, single in both valves ; nacre bluish white and iridescent. 

 Proc. Acad. Nat. Sci. 1859, p. 113. 



Hab. — Tombigbee River, Columbus, Mississippi. Wm. Spillman, M. D. 



My cabinet and cabinet of Dr. Spillman. 

 Diam. -7, Length IT, Breadth 1-9 inch. 



Shell smooth, elliptical, somewhat inflated, nearly equilateral, obtusely angular behind 

 and regularly rounded before ; substance of the shell thin, diaphanous behind ; beaks 

 somewhat prominent, with a few subconcentric undulations at the tips ; ligament 

 rather short, thin and light brown ; epidermis yellowish green, smooth, shining, with 

 broad, green rays, and well defined, small, yellow ones over the whole disk, with 

 distant, well marked lines of growth ; umbonial slope somewhat raised and rounded ; 

 posterior slope raised into a small keel, color yellow, with numerous, small, wavy 



