32 DESCRIPTION OF NEW 
Shell smooth, elliptical, somewhat inflated, inequilateral, obtusely angular behind; valves thick, beaks some- 
what prominent; epidermis dark-olive, rough, very much striate, obsoletely radiated ; cardinal teeth large, oblique, 
compressed and much erenulated; lateral teeth long, rather thick and curved; nacre white and iridescent. 
Hab. Columbia river, Oregon, Mr. C. M. Wheatley. 
Diath. 8, 2. Length 1.2, Breadth 2.1 inches. 
Shell smooth, elliptical, somewhat inflated, inequilateral, obtusely angular behind; sub- 
stance of the shell thick, thinner behind; beaks somewhat prominent, submedial; ligament 
rather short and somewhat thick; epidermis dark-olive, very rough, and striate over the 
whole disk, with very obscure, rather thin rays; posterior slope somewhat compressed ; 
umbonial slope obtusely angular; cardinal teeth large, oblique, compressed and much 
crenulated, double in the left and single in the right valve; lateral teeth long, rather thick, 
curved, enlarged at the posterior end and separated from the cardinal tooth; anterior 
cicatrices distinct; posterior cicatrices distinct; dorsal cicatrices placed obliquely on the 
inner portion of the cardinal tooth and under the plate; palleal cicatrix impressed ; cavity 
of the shell rather shallow; cavity of the beaks shallow and subangular; nacre white and 
iridescent. 
Remarks.—I owe to the kindness of Mr. Wheatley one of the two specimens before 
me. It is a species very distinct from any I am acquainted with. The roughness of the 
exterior is remarkable, and would indicate its inhabiting near to brackish waters. It is 
not usual to see a rough shell like this with rays. In those specimens which are eroded 
and old, they are indistinct; but I suspect that when perfect the rays might be very dis- 
tinct. In outline, it is somewhat like a young U. ligamentinus, Lam., (crassus, Say,) and 
the nacre is of the same pure white, but the surface is totally different, being rough, and 
the form more transverse. In its elliptical outline it comes closer to U. Sapotalensis, 
(Nobis,) but is a smaller shell, and differs much in the rays and the surface. 
Unio Rumpmanus. Pl. XXII. Fig. 34. 
Testa tuberculatd, quadratd, subinflatd, subinequilaterali, postice truncata, ad basim emarginatd; valvulis 
percrassis; natibus crassis, prominentibus; epidermide rufo-fuscd, substriatd; dentibus cardinalibus percrassis 
striatisque; lateralibus brevibus rectisque; margarita argented et iridescente. 
Shell tuberculate, quadrate, somewhat inflated, rather inequilateral, truncate behind, emarginate at the basal 
margin; valves very thick; beaks thick and prominent; epidermis reddish-brown, substriate ; cardinal teeth very 
thick and striate; lateral teeth short and straight; nacre silver white and iridescent. 
Hab. West Georgia? Dr. Budd. 
Cabinet of Dr. Budd, New York. 
Diam. 1.1, Length 1.7, Breadth 2 inches. 
Shell tuberculate, quadrate, somewhat inflated, rather inequilateral, truncate behind, 
emarginate at the basal margin, raised over the umbonial slope and grooved from beaks 
to basal margin; substance of the shell very thick, thinner behind; beaks thick, submedial 
and prominent; ligament short and thick; epidermis reddish-brown, somewhat striate, 
with distinct, proximate marks of growth; posterior slope compressed, raised into a carina 
and covered with curved rows of tubercles; umbonial slope raised into a widening ridge, 
