UNITED STATES, 85 



in alcohol. The figure i.s of a male. The females are sliifhtly enlarged over the 

 umbonial slope. It belongs to the ayinplanaliis group, and is near to confcrhis and 

 rrifusculus (nobis.) It is more compressed, and the beaks are more terminal than in 

 the first, and is not so much inflated, but more oblique than the latter. It is also 

 near to opactis (nobis) from the same locality. It is more oblique, more compressed, 

 and not so dark in the epidermis as that species, and the cardinal teeth are usually 

 smaller. All the specimens received were entirely purple in the nacre, except one, 

 which had a tint of salmon color mixed with the purple, and a partially white an- 

 terior margin. The undulations of the beaks are, in perfect young specimens, very 

 distinct and very closely resemble those of cnmplanatus. Some of the young are rayed 

 nearly over the whole disk. 



Unio rufus. pi. 17, fig. 65. 



Tcstii Itevi, transversa, valde compressa, ad latere planulatfi, postice subbiangulata, valde inaerjuilaterali ; 

 valvulis subcrassis ; natibus prominulis ; acuminatis ; epidermide rufo-fu.sca, eradiata ; dentibus cardi- 

 nalibus parvis, obtuso-conicis crenulatisque ; lateralibus sublongis, subcrassis, curvisque ; margaritfi 

 caeruleo-albil et irideseente. 

 Shell smooth, transverse, much compressed, flattened at the side, subbiangular be- 

 hind and very inequilateral ; valves somewhat thick; beaks a little prominent, some- 

 what pointed ; epidermis reddish brown, without rays ; cardinal teeth small, obtusely 

 conical and crenulate ; lateral teeth rather long, somewhat thick and curved; nacre 

 bluish white and iridescent. 



Proc. Acad. Nat. Sci., 1857, p. 171. 

 Hub. — Etowah River, Cass County, Georgia. Bishop Elliott. 

 My cabinet and cabinet of Bishop Elliott. 

 Diam. -6, Length 1-1, Breadth 1-9 inches. 



Shell smooth, transverse, much compressed, flattened at the sides, very inequilateral, 

 subbiangular behind and regularly rounded before; substance of the shell rather 

 thick, slightly thicker before ; beaks a little prominent and somewhat pointed ; liga- 

 ment rather long and thin ; epidermis reddish brown, darker on the posterior slope, 

 without rays, shining on the umbones and striate at the margin; umbonial slope 

 slightly raised into an obtuse angle ; cardinal teeth small, obtusely conical and crenu- 

 late ; lateral teeth rather long, somewhat thick and curved ; anterior cicatrices 

 distinct and well impressed ; posterior cicatrices confluent ; dorsal cicatrices placed 

 under the plate posterior to the cardinal teeth ; cavity of the shell very shallow ; 

 cavity of the beaks shallow and obtusely angular ; nacre bluish white and iridescent. 



Soft Paris. — Branchial uterm not charged, but ova were found in the ova- 

 rium of the two specimens received. Branchice large, thin, much rounded below, 

 inner ones much the larger, free more than half the length of abdominal sack. Palpi 

 small, suboval. united only at tlio upper part of the posterior edges. Mantle very 



