PNITED STATES. 91 



UnIO SIMILIS. PI. 19, fig. 71. 



Testa laevi, elliptic:!, subinflata, postice subbiangulata, vald6 inxquilaterali ; valvulis subcrassis ; natibus 

 prominulis ; epidermide tenebrosofuseii, radiata, polity ; dentibus cardinalibus subgrandibus, subclcva- 

 tis ct subpyratnidatia ; latcralibus sublongis subcurvisque ; margarita vcl purpurcik. vcl alba vol salmonis 

 colore tinctii et irideseente. 

 Shell smooth, elliptical, somewhat inflated, very inequilateral, subbiangular be- 

 hind ; valves somewhat thick ; beaks a little prominent ; epidermis dark brown, 

 radiated and polished; cardinal teeth rather large, somewhat elevated and pyramidal ; 

 lateral teeth somewhat long and cui'ved ; nacre purple, white or salmon color and 

 iridescent. 



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



//rt&.^Buckhead Creek, Burke County, Georgia. Bishop Elliott. 



My cabinet and cabinet of Bishop Elliott. 

 Diam. -8, Length 12, Breadth 2-3 inches. 



Shell smooth, elliptical, somewhat inflated, inequilateral, obtusely biangular behind 

 and subtruncate before; substance of the shell somewhat thick, slightly thicker 

 before ; beaks a little prominent ; ligament rather long and somewhat thick ; epider- 

 mis dark brown, radiated over the whole disk, polished on the umbones and striate 

 near the margin, with obscure rather distant lines of growth; umbonial slope raised 

 and very much rounded ; cardinal teeth rather large, somewhat elevated into a pyra- 

 midal form, crenulate and slightly disposed to be double in the right valve ; lateral 

 teeth somewhat long, lamellar and slightly curved ; anterior cicatrices distinct and 

 deeply impressed ; posterior cicatrices confluent, large and indistinctly impressed ; 

 dorsal cicatrices small, and placed in the centre of the cavity of the beaks ; ca^aty of 

 the shell rather deep and wide ; cavity of the beaks shallow and rounded ; nacre 

 purple, white or salmon color and iridescent. 



Soft Parts. — Branchial uteriis filling nearly the whole of the outer branchiae Bran- 

 rhim moderately large, rounded below, the inner ones somewhat the larger, free three 

 fourths of the length of the abdominal sack. Palpi small, suboval, thin, united only 

 at the upper part of the posterior edges. Mantle thin, slightly thickened at the 

 margin. Brancliial opening rather large, with numerous dark brown papilla> on the 

 inner edges. Anal opening large, with numerous very minute brown papilUu on the 

 inner edges. Siiper-anal opening large, slightly colored within and united below for 

 a short distance. Color of the mass whitish. 



Embryonic shell clear white and very nearly the same form as Othcaloogensis (nobis.) 



Bemarks. — This belongs to the group of which Geildingsianns, (nobis,) may be con- 

 sidered the type. It is near to Whiteianus (nobis.) Its epidermis is polished like 

 both .species. In the character of the rays it resembles Geddingsiantis. It is less 

 polished on the side.-; than Whitrirnm.s, which usually has no rays. 



