﻿UNITED STATES. 59 



within the cavity of the beaks ; cavity of the shell very shallow; cavity of the beaks 

 shallow and subangular ; nacre pure white, and very iridescent. 



Soft Parts. — Branchial uterus occupies the whole leaf of the outer branchiae. Bran- 

 chioe rather large, nearly semi-circular, inner ones much the larger, free nearly the 

 whole length of the abdominal sack. Palpi small, oblique, subtriangular, rather thin, 

 united but a short distance on the posterior edge. Mantle very thin, thickened, and 

 slightly colored at the margin. Branchial opening rather large, with numerous very 

 small light brown papillae on the inner edges. Anal opening very small, Avith minute 

 light brown papillae. Super-anal opening very long, slightly colored within the edges, 

 and very slightly united below. Color of the mass whitish. 



Remarks. — Among the numerous new TJniones sent by Bishop Elliott, were many 

 fine specimens of this beautiful species, which is rarely more than two inches wide. 

 In outline it approaches the U. rubiginosis, (nobis,) and U. Bigbyensis, (nobis,) and 

 more particularly the latter ; but it is not quite so much compressed, nor are the rays 

 alike, the favosus having broad green spots, usually in a single row, on the space between 

 the marks of growth, and immediately before the umbonial slope, while the Bigbyensis 

 is rayed all over with usually thin lines, and in the epidermis it is more yellow. In the 

 undulations of the beaks they also differ, the latter having numerous rather small 

 ones, while favosus has but two or three, and these are rather rough, and almost tu- 

 berculose. The largest green spot is usually on the third growth near the middle. 



Unio rutilans. PL 9, fig. 41. 



Testa laevi, elliptica, inflata, valde inasquilaterali, in medio ad basim paulisper compressa ; valvulis tenuibus ; 



uatibus prominulis ; epidermide luteo-viridi, polita et valde radiata ; dentibus cardinalibus parvis, com- 



pressis, in utroque valvulo duplicibus; lateralibus pralongis, lamellatis subcurvisque; margarita eseruleo- 



alba et valde iridescente. 



Shell smooth, elliptical, inflated, very inequilateral, somewhat compressed in the 



middle towards the base ; valves thin ; beaks a little prominent ; epidermis yellowish 



green, polished and very much radiated ; cardinal teeth small, compressed, double in 



both valves ; lateral teeth very long, lamellar and somewhat curved ; nacre bluish 



white and very iridescent. 



Prc-c. Acad. Nat. Sci. 1856, p. 262. 

 Eab. — Othcalooga Creek, Gordon County, and Columbus, Georgia. Bishop Elliott. 

 My cabinet and cabinet of Bishop Elliott. 

 Diam. "1, Length 1-4, Breadth 2*7 inches. 



Shell smooth, elliptical, inflated, very inequilateral, somewhat compressed in the 

 middle towards the base, rounded before and behind ; substance of the shell very thin, 

 thicker before ; beaks a little prominent, and with a few small irregular undulations 

 at the tip ; ligament rather short and thin ; epidermis yellowish green, polished, with 

 numerous rays, the broader ones on the posterior portion ; cardinal teeth small, com- 

 pressed, pointed, double in both valves; lateral teeth very long, thin, lamellar and 



