﻿UNITED STATES AND NORTHERN MEXICO. 333 



transverse, united only at the upper portion of the posterior edges. Mantle thin, 

 whitish, thickened at the border. Branchial opening large, with numerous very dark 

 brown papillae on the inner edges. Super-anal opening very large, colored on the 

 inner edges and united below. Color of the mass whitish. 



Remarks. — T have quite a number of this species from Bishop Elliott and Mr. Hal- 

 lenbeck, but none with the soft parts. In outline it is very near to Roswellensis 

 (nobis), but it is rather more transverse and less compressed. In the color of the epi- 

 dermis it is very different, that species being dark brown or nearly black, while this 

 is usually light or reddish brown. In the cardinal teeth they also differ, the sale- 

 brosus being single in the right valve, while in the other it is double. It is allied on 

 the other side to Ballenbeckii (nobis), but is a much wider shell and is more biangu- 

 lar at the posterior margin. Several of the specimens have well defined ventral cica- 

 trices. 



Unio inusitatis. PI. 52, fig. 158. 



Testa lasvi, oblonga, subeompressa, ad latere planulata et contracts, postice obtuse biangulata, valde insequi- 

 laterali; valvulis crassiusculis ; natibus prominulis, ad apices minute undulata; epidermide lutea et 

 fusca, superne glabra, inferne tenebroso-striata, obsolete radiata ; dentibus cardinalibus parvis, acumi- 

 natis, crenulatis, in utroque valvulo duplicibus; lateralibus longis, lamellatis subrectisque ; mar^arita 

 vel alba vel purpurea vel salmonis colore tincta et valde iridescente. 



Shell smooth, oblong, rather compressed, flattened at the sides and contracted, ob- 

 tusely angular behind, very inequilateral ; valves somewhat thick ; beaks slightly 

 prominent and minutely undulate at the tip, epidermis yellowish and brown, smooth 

 above and dark and striate below ; cardinal teeth small, pointed, crenulate, double in 

 both valves; lateral teeth long, lamellar, and nearly straight ; nacre white, purple or 

 salmon color, and very iridescent. 



Proc. Acad. Nat. Sci. 1859, p. 171. 



Hob. — Swift Creek, below Macon, Georgia. Bishop Elliott. 



My cabinet and cabinet of Bishop Elliott. 

 Diam. -8, Length 1-2, Breadth 2-3 inches. 



Shell smooth, oblong, rather compressed, flattened at the sides and contracted at 

 the second growth, obtusely angular behind and regularly rounded before, very ine- 

 quilateral ; substance of the shell somewhat thick ; beaks slightly prominent, with 

 numerous small, closely set undulations, which are angular on the umbonial slope • 

 ligament rather long and somewhat thick; epidermis obscurely radiate and smooth 

 above, striate and usually banded with yellow below ; umbonial slope slightly raised 

 and obtusely angular ; posterior slope raised into a rather sharp carina and usually 

 with two obscure impressed lines in each valve; cardinal teeth small, pointed, crenu- 

 late, double in both valves, but only slightly so in the left one; lateral teeth lono- 



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