UNIO 699 
when young, dark brown or black and rough in old shells; 
pseudocardinals rough, scarcely compressed, double in both 
valves; laterals long and straight, inclined to be club-shaped, 
granulated ; anterior muscle scars impressed, separate; poste- 
rior scars well-marked, elongated; nacre coppery, chocolate, 
dull purple or white, dull to brilliant. 
Length 190, height 44, diam. 25 mm. 
Altamaha River, Georgia. 
Type locality, Hopeton, near Darien, Ga. 
Unio shepardianus Lea, Tr. Am. Phil. Soc., V, 1834, p. 95, pl. 
xu, fig. 38; Obs., I, 1834, p. 207, pl. x11, fig. 38.—Conrap, 
Monog., VIII, 1837, p. 70, pl. xxx1x.—HAn _ey, Biv. Shells, 
1843, p. 203, pl. xx1u, fig. 25.—KustTeER, Conch. Cab. Unio, 
1852, p. 65, pl. xvi, fig. 1—?CHENU, Man., 1859, II, p. 139, 
fig. 647.—RereEvE, Conch. Icon., XVI, 1865, pl. xrx, fig. go.— 
SIMPSON, Syn., 1900, p. 737. 
Vargarita (Unio) shepardianus Lea, Syn., 1836, p. 34; 1838, 
p. 23. 
Margaron (Unio) shepardianus Lea, Syn., 1852, p. 35; 1870, 
P. 57: 
Unio sheppardianus CatLow and Reeve, Conch. Nom., 1845, 
p. 64. 
This species is unique and need never be mistaken for any 
thing else. The specimen measured is one of the largest I 
have seen; it is somewhat rayed behind and has a white nacre. 
The shells in a superficial way sometimes resemble some of 
the Chinese forms, but they are generally more arcuate; they 
are wider behind than in front and attain a much greater size. 
Group of Unio popeii. 
Shell elongated, narrowed in front, and biangulate behind, 
with the base slightly sinuate, feebly sulcate; beaks not prom- 
inent, sculptured with rather fine, somewhat broken, often faint 
ridges, which have a tendency to fall into two rounded loops ; 
pseudocardinals compressed, high, sharp, ragged ; laterals Jong, 
slightly curved; cavity of the beaks shallow; cicatrices not 
deep. The shell is only a little thickened in front, and that of 
the female is slightly swollen at the posterior base. 
