10 DESCRIFTION OP NEW 



Unio sordidis. pi. XII. Fig. I. 



Ttita lirvi, tHijUkn, sithcompressn, ineqnilatera/i, poslice rotvndata ; vn/vulis siibcrassis ; nallbus promi- 

 mi/is; epidertniile riifo-fiisca, striata; dentibus cardinalibus parvis ; lateralibus longis subrectisque ; marga- 

 rild alba et iridescentc. 



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

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

 white and iridescent. 



Ilab. Abbeville District, S. C. J. l\ Barratt, M. D. 

 My cabinet, 

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



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

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

 ligament long and thick; epidermis roddish-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 leevi, cUiptica, sichcompressti, ine/juilaterati, postice snbbiangnlatu ; vtilvulis siibcmssis ; natibus 

 prominentibiis : tpidennide hilco-fuscn, rudial/i, striata: dentibus cardinalibtifi parvis, tripartili.i ; lulcralibus 

 pradongis su/)reclistjtif ; viargurilit alba et iridescenle. 



Shell smooth, elliptical, somewhat compressed, inequilateral, sidibiangular behind; valves rather thick; beaks 

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

 nearly straight ; nacre white and iridescent. 



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

 My cabinet, 

 Diam. 1, Length L5, Breadth 2.8 inches. 



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

 biangular behind; 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 j)osterior end, se[)aratcd from 

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



