86 NEW UNlONIDi?i; OF THE 



thin, with a broad border, slightly colored at the edge. Branchial opening rather 

 large, with numerous small brown papillas on the inner edges. Anal (ypenimj rather 

 large, with very minute brown papillge on the inner edges. Super-anal opening 

 rather small, slightly colored within and united below for a short distance. Color of 

 the mass whitish. 



Bemarlis. — Only two specimens were received and these are not probably full 

 grown. The largest being only one and three-quarter inches wide. It is very nearly 

 allied to pliaseolus, Hild., the outline being very nearly the same, but the posterior 

 slope is higher than in that species. It is very much compressed at the sides and the 

 basal margin is nearly or quite straight. There are no rays on the two before me, 

 but more perfect specimens may sometimes be rayed. 



Unio opacus. pi. 18, fig. 66. 



Testa Iffivi, ellipticri, subinflata, postic^ biangulata, inscquilaterali ; valvulis subcrassis ; natibus prominulis • 

 epidermide vel tenebroso-fusca vel nigricente, subnitens ; dentibus cardinalibus subgrandibus, elevatis, 

 subpyramidatus crenulatisque ; lateralibus longis, lamellatis subrectisque ; margarita purpurea et 

 iridescente. 



Shell smooth, elliptical, rather inflated, biangular behind, inequilateral ; valves 

 rather thick ; beaks a little prominent ; epidermis very dark brown or blackish ; 

 somewhat shining ; cardinal teeth rather large, erect, subpyramidal and crenulate ; 

 lateral teeth long, lamellar and nearly straight ; nacre purple and iridescent. 

 Proc. Acad. Nat. Sci. 1857, p. 169. 



Hah. — Buckhead Creek, Burke County. Georgia. Bishop Elliott. 



My cabinet and cabinet of Bishop Elliott. 

 Diam. 1, Length 1-5, Breadth 2-7 inches. 



Shell smooth, elliptical, somewhat inflated, biangular behind and slightly truncate 

 before, inequilateral ; substance of the shell rather thick ; beaks a little prominent ; 

 ligament rather short and somewhat thick ; epidermis very dark brown, almost black, 

 shining on the umbones and rather roughly striate towards the margin ; umbonial 

 slope somewhat raised and obtusely angular ; cardinal teeth rather large, erect, some- 

 what pyramidal, crenulate, disposed to be double in both valves ; lateral teeth long, 

 lamellar and nearly straight; anterior cicatrices distinct and well impressed ; posterior 

 cicatrices confluent and slightly impressed ; dorsal cicatrices nearly in the centre of 

 the beaks ; cavity of the shell rather shallow and wide ; cavity of the beaks very 

 shallow and round ; nacre purple and iridescent. 



BemarJcs. — This belongs to that portion of the complanatus group which includes 

 canfertus, ohnuhilus, geminus and Leconiii. It has a very regularly elliptical outline. At 

 the posterior margin, where the two obtuse angles are formed, there is a slight twist 

 which seems to be natural to this species. 



