254 DESCRIPTION OF NEW 



Unio sordidis. PI. XII. Fig. 1. 



Testa Irevi, ellipticd, subcompressd, inequilaterali, postici rotundatd ; valvulis subcrassis ; natibus promi- 

 nulls; epidermide rufo-fusca, striata; denlibus cardinalibus parvls ; laleralibus longis subrectisque ; marga- 

 ritd alba et iridescente. 



Shell smooth, elliptical, rather compressed, inequilateral, rounded behind ; valves rather thick ; beaks slightly 

 prominent; epidermis reddish-brown, striate ; cardinal teeth small ; lateral teeth long and nearly straight ; nacre 

 white and iridescent. 



Hab. Abbeville District, S. C. J. P. Barratt, M. D. 

 My cabinet. 

 Diam. .8, Length 1.3, Breadth 2.4 inches. 



Shell smooth, elliptical, rather compressed, inequilateral, rounded before and behind ; sub- 

 stance of tbe shell rather thick, thinner behind ; beaks slightly prominent and nearly terminal; 

 ligament long and thick; epidermis reddish-brown, obtusely rayed, with obscure equidistant 

 marks of growth; umbonial slope rounded; cardinal teeth very small and striate, single 

 in the right and double in the left valve; lateral teeth long and nearly straight, separated 

 from the cardinal tooth; anterior cicatrices distinct; posterior cicatrices confluent; dorsal 

 cicatrices nearly in the centre of the cavity of the beak, under the cardinal tooth; cavity 

 of the shell shallow; cavity of the beaks very shallow and subangular; nacre white and 

 iridescent. 



Remarks. — A single imperfect specimen only of this was received by me, and I hesitated 

 for some time to describe it, in hopes of getting more to determine its characters better, 

 It is certainly very much like the widely distributed U. complanatus; but it seems to me to 

 differ in its form, being more rounded behind, more rounded over the umbones, and more 

 compressed over the umbonial slope. 



Unio Gibbesianus. PI. XII. Fig. 2. 



Testa Isevi, elliptica, subcompressd, inequilateral!, postice subblangulatd ; valvulis subcrassis ; natibus 

 prominentibus ; epidermide luteo-fuscd, radiatd, striata; denlibus cardinalibus parvis, tripartills; lateralibus 

 pr.r/ongls subrectisque; margarild alba ct iridescente. 



Shell smooth, elliptical, somewhat compressed, inequilateral, stibbiangular behind; valves ralher thick; beaks 

 prominent; epidermis yellowish-brown, radiated, striated; cardinal teeth small; lateral teeth very long and 

 nearly straight; nacre white and iridescent. 



Hab. Abbeville District, S. C. Louis R. Gibbes, M. D. 

 My cabinet. 

 Diam. 1, Length 1.5, Breadth 2.8 inches. 



Shell smooth, elliptical, somewhat compressed, inequilateral, rounded before and sub- 

 biangular behind j substance of the shell thick; beaks prominent and submedial; ligament 

 long and very thick; epidermis yellowish-brown, obscurely radiated, roughly striate near 

 the margin, smooth on the umbones, marks of growth nearly equidistant and distinct; 

 umbonial slope rounded; cardinal teeth small, slightly elevated, pointed and tripartite; 

 lateral teeth very long, nearly straight and thickened at the posterior end, separated from 

 the cardinal tooth; anterior cicatrices distinct; posterior cicatrices distinct; dorsal cica- 



