FRESH WATER AND LAND SHELLS. 27 
sidered the type. In its outline it approaches the /uéeolus, Lam., but is not quite so trans- 
verse, while it is more so than cariosus. Two of the specimens are richly salmon-coloured 
in the cavity of the shell—the others are all white. ‘The females are very much enlarged 
over the umbonial slope, and expanded at the posterior basal margin. None of the speci- 
mens which I received have any rays. 
I have named this species in honour of Prof. W. Byrd Powell, of Memphis, Tenn. 
Unio arrinis. Pl. XIX. Fig. 26. 
Testa levi, elliptica, convexd, inequilaterali, posticé rotundata; valvulis subtenuibus; natibus subpromi- 
nentibus ; epidermide radiata, luteold, nitida; dentibus cardinalibus parvis, compressis, obliquis, acuminalis, 
crenulatis ; lateralibus sublongis, lamellatis subcurvisque; margarita alba et iridescente. 
Shell smooth, elliptical, convex, inequilateral, rounded behind; valves rather thin; beaks rather prominent, 
epidermis rayed, yellowish, shining; cardinal teeth small, compressed, oblique, acuminate, crenulate; lateral 
teeth rather long, lamellar and rather curved; nacre white and iridescent. 
Hab. Alexandria, Louisiana, J. Hale, M. D. 
My cabinet. 
Diam. .9, Length 1.4, Breadth 2.1 inches. 
Shell smooth, elliptical, convex, inequilateral, rounded behind and inflated over the 
umbones; substance of the shell rather thin; beaks rather prominent, placed towards the 
anterior margin; ligament rather short and somewhat thick; epidermis shining, yellowish, 
with numerous rays and rather distant marks of growth; posterior slope rather elevated ; 
umbonial slope rounded and inflated; cardinal teeth small, compressed, oblique, acuminate, 
crenulate, double in both valves; lateral teeth rather long, lamellar, slightly curved, 
separated from the cardinal tooth; anterior cicatrices distinct; posterior cicatrices con- 
fluent; dorsal cicatrices placed across the cavity of the beak under the cardinal tooth; 
cavity of the shell rather deep and rounded; cavity of the beaks rather shallow and sub- 
angular; nacre white and iridescent. 
Remarks.—The outline of the specimen before me is of a remarkably regular oval. It 
belongs to the group of which cariosws, Say, may be considered the type. It is nearest in 
general character to U. crocatus, (Nobis,) but it is a larger species, not angular behind, 
and the rays are broader. 
Unio proximus. Pl. XX. Fig. 27. 
Testé levi, ellipticd, subinflata, subinxquilaterali, posticé rotundatd; valvulis tenuibus 3 natibus parvis, 
subprominentibus; epidermide luted, radiata; dentibus cardinalibus valdé compressis, obliquis, acuminalis ; 
lateralibus longis, lamellatis subrectisque; margarita alba et iridescente. 
Shell smooth, elliptical, somewhat inflated, subinequilateral, rounded behind; valves thin; beaks small, some- 
what prominent; epidermis yellowish, radiated; cardinal teeth much compressed, oblique, acuminate; lateral 
teeth long, lamellar and nearly straight; nacre white and iridescent. 
Hab. Georgia. J. P. Barratt, M.D. 
My cabinet and cabinet of Dr. Barratt. 
Diam. .7, Length 1.2, Breadth 2.1 inches. 
