FRESH WATER AND LAND SHELLS. 41 
Anoponra penicrATA. Pl. XXV. Fig. 45. 
Testa levi, ellipticd, convexiusculd, inxquilaterali, antice rotundata valvulis tenuibus; natibus prominu- 
lis, ad apices undulatis ; epidermide polita, bruneo-nigricente, obsoleté radiata; margarita cxrulea alba et 
iridescente. 
Shell smooth, elliptical, somewhat inflated, inequilateral, rounded before; valves thin, beaks slightly prominent, 
undulated at the tip; epidermis polished, blackish-brown, obscurely rayed; nacre bluish-white and iridescent. 
Hab. Campbell county, East Tennessee, President Estabrook. 
My cabinet and cabinet of President Estabrook. 
Diam. .8, Length 1.2, Breadth 2.2 inches. 
Shell smooth, elliptical, somewhat inflated, inequilateral, rounded before and very 
slightly flattened on the anterior part, with a slightly curved dorsal line a little irregular 
near the point of the beak; substance of the shell thin, very slightly thicker and whiter 
before; beaks very small and very slightly prominent, rather concentrically undulate at 
the tip; ligament thin and rather long; epidermis polished, blackish-brown, sometimes 
dark-greenish-brown, and obtusely rayed, with distant marks of growth. Posterior slope 
rather wide, and not much compressed; with three rather obscure dark-green rays, from 
the beak to the posterior margin; umbonial slope rounded and but slightly raised; anterior 
cicatrices confluent; posterior cicatrices confluent; dorsal cicatrices immediately above 
the centre of the cavity of the beaks; cavity of the shell not very deep, oval; cavity of 
the beaks very shallow and rounded; nacre bluish-white and iridescent. 
Remarks.—This is rather a small species, of which President Estabrook sent me some 
dozen specimens. It is a distinct species, and more nearly allied to An. Ferussaciana, 
(Nobis,) than to any other species. It differs in being a smaller species, in being more 
compressed, and in having a much less callus on the dorsal margin. Indeed, in some of 
the specimens no callus can be perceived. The undulations of the beaks are simple and 
nearly concentric, like the Ferussaciana, but they are smaller. In all the specimens but a 
half-grown one, there is a rough, opake, white, carious mark of disease about the anterior 
cicatrix and the cavity of the beaks. The younger one is without this mark of disease. 
This specimen is greenish, and has the lines of growth very distinctly marked. 
Anoponta opaca. Pl. XXV. Fig. 46. 
Testa levi, ellipticd, subinflata, inxquilaterali, postice angulata; valvulis tenuibus; natibus subpromi- 
rentibus, ad apices undulatis ; epidermide opacd, nigricente, obsolete radiaté ; margarita alba et iridescente. 
Shell smooth, elliptical, rather inflated, inequilateral, angular behind; valves thin, beaks rather prominent, 
undulate at the tip; epidermis dark, almost black, obscurely rayed; nacre white and iridescent. 
Hab. Near New Orleans, Mons. Janin. Little Rock, Arkansas, Prof. Powell. 
My cabinet and cabinets of Prof. Powell and Dr. Hale. 
Diam. 1.5, Length 2.1, Breadth 3.4 inches. 
Shell smooth, elliptical, rather inflated, inequilateral, angular behind, slightly curved on 
the dorsal line; substance of the shell thin; beaks rather prominent and undulated at the 
tip; ligament rather short and somewhat thick; epidermis dark, almost black, coarsely 
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