UNIO 669 
the posterior base; base line nearly straight, sometimes pro- 
duced a little towards the posterior end; surface with fine, un- 
even growth lines; epidermis dirty or brownish-green and 
sometimes rayed in young shells, brown or blackish in old 
shells, scarcely shining; pseudocardinals smail and low, gen- 
erally cross striated, often ill-defined; there are two short lat- 
erals in the left valve and one in the right ; beak cavities shal- 
low ; muscle scars impressed ; nacre flesh-color or purplish, gen- 
erally bright and iridescent behind. 
Length 120, height 65. diam. 38 mm. 
Length 96, height 43, diam. 28 mm. 
Length 135, height 65, diam. 33 mm. 
Length 140, height 75, diam. 43 mm. 
Georgia, in streams flowing into the Atlantic ; Santee Canal, 
South Carolina. 
Type locality, Hopeton, near Darien, Ga. 
Unio hopetonensis Lea, Tr. Am. Phil. Soc., VI, 1838, p. 29, 
pl. 1x, fig. 24; Obs., II, 1838, p. 29, pl. rx, fig. 24.—HANLEy, 
Biv. Shells, 1843, p. 198, pl. xx, fig. 21 —CHENu, Il. Conch., 
1858, pl. xx, figs. 5, 5a, 5b—Kuster, Conch. Cab. Unio, 
1861, p. 196, pl. Lxit, fig. 1.—Sowersy, Conch. Icon., XVI, 
1868, pl. Lxvil, fig. 349.—Simpson, Pr. U. S. Nat. Mus., 
DeVe AGO2) p.4i2, pl ian, fis ss ta, iis: 1; Syn., 1900, p. 728. 
Margarita (Unio) hopetonensis Lea, Syn., 1836, p. 30; 1838, 
p21. 
Margaron (Unio) hopetonensis Lea, Syn., 1852, p. 323; 1870, 
pel 
A rather fine, large species with a peculiarly tinted epider- 
mis and usually rich, brilliant nacre. In a great many speci- 
mens the pseudocardinals are feebly developed and not well 
separated, and are decidedly cross-striated. 
UNIO LIVINGSTONENSIS Lea. 
Shell subrhomboid, being narrower in front than behind, 
thin, not inflated, its greatest diameter being at the posterior 
ridge and in front of this it is wedge-shaped, inequilateral ; 
beaks low, somewhat compressed, their sculpture not seen: 
