602 UNIO 
subangular or somewhat rounded, often somewhat double, 
ending behind a little below the median line, usually in a faint 
biangulation; surface unevenly concentrically striate; epider- 
mis, finely lamellose, dull olive or dirty green, rarely showing 
a few faint rays; left valve with two low, stumpy pseudocard- 
inals and two laterals; right valve with one or two pseudo- 
cardinals, the upper apparently small, and one lateral; nacre 
bluish-white, tinted with flesh-color in the cavities, with an 
oblique furrow. 
Length 50, height 26, diam. 14 mm. 
Georgia; Florida; Yadkin River, North Carolina? 
Type locality, Coosawattee River, Murray Co., Ga. 
Unio luridus Lea, Tr. Am. Phil. Soc., X, 1852, p. 273, pl. xx, 
fig. 29; Obs., V, 1852, p. 29, pl. xx, fig. 29.—SIMPSON, Syn., 
Igoo, p. 705. 
Margaron (Unio) luridus Lea, Syn., 1852, p. 30; 1870, p. 48. 
Possibly only a small variety of U. gibbosus. It has no 
decided characters, but is small, compressed, moderately solid, 
and usually a little produced in the post-basal region. 
Group of Unio discus. 
Shell large, solid, compressed, subtriangular ; biangulate be- 
hind; beak sculpture not seen; beaks high, but not swollen; 
epidermis dark, rough; teeth heavy: laterals remote, club- 
shaped; nacre white, yellow, or purple. 
Animal unknown. 
Unio piscus (Lea). 
Shell large, subtriangular, compressed, solid, inequilateral ; 
beaks high but compressed, their sculpture not seen; posterior 
ridge low. double, ending behind in a biangulation about at 
the median line; anterior end narrowed and rounded; base 
line evenly curved, surface with strong, uneven, concentric 
sculpture ; epidermis, brownish or blackish, rayless; left valve 
with a strong, triangular pseudocardinal, often with a rudi- 
mentary tooth above it and another behind it, with one heavy, 
club-shaped lateral; right valve with two strong pseudocardi- 
