32 NEW UNIONID.^ OF THE 



I dedicate this species to Dr. Neislor, to whom I am indebted for many fine Georgian 

 Unio7iidcE. 



Unio Postellii. pi. 26, fig. 9i. 



Testa laevi, oblonga, valde compressa, posticfe subbiangulata, valde insequilaterali ; valvulis subcrassis ; 

 natibus prorainulis, ad apices undulatis ; epidermide tenebroso-fusca, transverse striata; dentibus 

 carJinalibus magnis, in utroquo valvulo duplieibus, erenulatis ; lateralibus praelongis, lamellatis sub- 

 rectisque; margarita vel alba, vol purpurea vel salmonis colore tincta et iridescente. 



Shell smooth, oblong, much compressed, subbiangular behind, very inequilateral ; 

 valves somewhat thick; beaks a little prominent, undulate at the tip; epidermis 

 very dark brown and transversely striate ; cardinal teeth large, crenulate and double 

 in both valves; lateral teeth verj^ long, lamellar and nearly straight ; nacre white, 

 purple or salmon color and iridescent. 

 Proc. Acad. Nat. Sci., 1858, p. 165. 



Hah. — Eandall's Creek, near Columbus, Georgia, Bishop Elliott, and Carter's Creek, 

 Baldwin County, Georgia, J. Postell, Esq. 



My cabinet and cabinets of Bishop Elliott and Mr. Postell. 

 Diam. -8, Length VI, Breadth 3--4 inches. 



Shell smooth, oblong, much compressed, subbiangular behind, much flattened on 

 the sides, very inequilateral ; substance of the shell somewhat thick, very slightly 

 thicker before; beaks a little prominent, with small, nearly parallel undulations at 

 the tips ; ligament long, thick and light brown ; epidermis dark brown, striate and 

 with distant marks of growth ; umbonial slope very slightly raised into an obtuse 

 angle ; posterior slope slightly raised and furnished with two impressed lines on each 

 valve from the beaks to the posterior margin, sometimes causing there an emargin.a- 

 tion ; cardinal teeth large, crenulate, nearly perpendicular and double in both valves ; 

 lateral teeth very long, lamellar, granulate and nearly straight; anterior cicatrices 

 distinct, very large and deeply impressed; posterior cicatrices confluent, large and 

 slightly impressed ; dorsal cicatrices nearly in the centre of the cavity of the beaks ; 

 cavity of the shell very shallow and wide ; cavity of the beaks ver3^ shallow and 

 rounded ; nacre white or salmon color and iridescent. 



Soft parts. — Branchial titerus occupies the whole width of the outer branchiae. 

 Brancliice very wide, straight below, inner ones slightly the larger, free two-thirds of 

 the length of the abdominal sack. Palpi large, transverse, suboval, united only at 

 the upper portion of the posterior edges. Mantle thin, thicker at the margin, where it 

 is slightly colored. Branchial opening small, with rather small brownish papillae. 

 Anal opening rather large, with small papillae on the inner edges. Super-anal opening 

 rather large, slightly colored on the inner edges and slightly attached below. Color 

 of the mass whitish. 



Embryonic shell is pouch-shape and very closely allied to that of tortivm (nobis). 



