670 UNIO 
posterior ridge imperfectly double, the main ridge ending be- 
hind at the base of the shell, above this the outline is irregularly 
curved up to the dorsal line; surface with uneven growth lines ; 
epidermis of different shades of greenish-brown, cloth-like 
when fresh; pseudocardinals small, double in the left and sin- 
gle in right valves; laterals remote, delicate, curved; muscle 
scars shallow ; nacre bluish or greenish-white to purplish. 
Length 68, height 40, diam. 22 mm. 
North Carolina to Georgia. 
Type locality, Livingston’s Creek, Brunswick Co., N. C. 
Unio liingstonensis Lea, Pr. Ac. N. Sci. Phila., VII, p. 192; 
jl. Ac. IN. Set; Philaz Vil, 1860;"p ei p lr io see Oboe 
XI, 1867, p. 18, pl. 1v, fig. 11.—Simpson, Syn., 1900, p. 720. 
Margaron (Unio) livingstonensis La, Syn. 1870, 9p. 52: 
Quite a distinct species for a member of the complanatus 
group. So far as I have seen the shell is always rather 
thin and narrower in front, its greatest inflation is at the pos- 
terior ridge and from that point forward it is wedge-shaped 
when viewed from above. The wide ‘posterior end is bounded 
by an uneven curved line, which shows one or two faint angles. 
The epidermis is rough, dark and cloth-like. 
UNI0 INUSITATIS Lea. 
Shell subrhomboid, higher behind than in front, inequilat- 
eral, rather thin, scarcely inflated, its greatest diameter being 
at the posterior ridge; beaks moderately full and elevated, 
their sculpture not seen; posterior ridge high, subangulate, 
ending below in a blunt point at the base of the shell; surface 
with irregular, concentric sculpture; epidermis tawny-brown- 
ish and greenish, rather bright; pseudocardinals small, sub- 
compressed, double in the right valve and single in the left; 
laterals remote, short; muscle scars shallow, smooth; nacre 
lurid, purplish, brownish or coppery, brilliant and iridescent 
behind. 
Type locality, Swift Creek, below Macon, Georgia. 
