FRESH WATER AND LAND SHELLS. 271 



sidered the type. In its outline it approaches the luleolus; 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 affinis. PI. XIX. Fig. 26. 



Testa Isevi, ellipticd, convexd, inequilaterali, postice rotundatd; valvulis subtenuibus ; nalibus subpromu 

 nentibus; epidermide radiatd, luteold, nitidd; dentibus cardinalibus parvis, compressis, obliquis, acuminatis, 

 crenulatis; laleralibus sublongis, lamellalis subcuroisque ; mar garild alba et iridescente. 



Shell smooth, elliptical, convex, inequilateral, rounded behind; valves rather thin; beaks rather prominent, 

 epidermis raved, yellowish, shilling; cardinal teeth small, compressed, oblique, acuminate, crenulate; lateral 

 teeth rather long, lamellar and rather curved; nacre white and iridescent. 



Hah. Alexandria, Louisiana, J. Hale, M. D. 

 My cabinet. 

 Diam. .9, * Length 1.1, 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 cariosus, Say, may be considered the type. It is nearest in 

 general character to U. crocalus, (Nobis,) but it is a larger species, not angular behind, 

 and the rays arc broader. 



Unio proximcs. PI. XX. Fig. 27. 



Trxlti Isevi, eUipticd, subinflatd, subinmquilaterali, postice rotundatd; valvulis tenuibusj natibus parvis, 

 subprominentibus ; epidermidi luted, radiatd; dentibus cardinalibus vol vessis, obliquis, acuminatis ; 



laleralibus longis, lamellalis subrectisque ; margaritd alba et iridescente. 



Shell smooth, elliptical, somewhat inflated, suhincquilateral, 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. 



I lab. Georgia. J. P. Barratt, M. D. 



My cabinet and cabinet of Dr. Barratt. 

 Diam. .7. Length 1.2, Breadth 2.1 inches. 



