UNIO 675 
Very close to U. nawiculoides and probably only a variation 
of it. It is higher in proportion than that species, the poste- 
rior ridge is not so high and it is a little less concentrically 
sculptured. 
UNIO OBLATUS Lea. 
Shell subrhomboid, rather solid, convex, inequilateral ; beaks 
apparently not full or high; posterior ridge high, rounded, 
becoming feebly double below, ending behind in a faint biangu- 
lation below the median line; anterior end round; base nearly 
straight ; dorsal slope obliquely subtruncated ; surface thrown 
up into low, concentric ridges at the dark rest marks, otherwise 
nearly smooth; epidermis dark olive, smooth and shining; left 
valve with two stumpy pseudocardinals and two club-shaped 
laterals ; right valve with two pseudocardinals, the upper small, 
with one lateral ; anterior scars impressed ; posterior scars shal- 
low ; nacre dirty flesh-color; nacre thicker in front. 
Length 65, height 32, diam. 18 mm. 
Type locality, Long Creek, Gaston County, North Carolina. 
Unio ablatus Lea, Pr. Ac. N. Sci. Phila., VII, 1863, p. 193. 
Unio oblatus Lea, Jl. Ac. N. Sci. Phila., VI, 1866, p. 13, pl. rv, 
fig. 10; Obs. XI, 1867, p. 17, pl. v, fig. 10—SIMPson, Syn., 
TQO0, Pp. 730. 
Margaron (Unio) oblatus Lea, Syn., 1870, p. 60. 
Another puzzling nondescript. The surface of the only 
authentic shell I have seen, the type, is thrown up into low, 
concentric ridges at the rest marks, which are dark and nar- 
rowly spaced. The epidermis is dark olive, but shining; the 
nacre is much thickened in front. 
UNIO ERRANS Lea. 
Shell elongated, subrhomboid or subelliptical, compressed 
to convex, inequilateral; subsolid or rather thin; beaks low, 
not inflated, their sculpture a number of strong ridges, which 
run nearly parallel with the growth lines and are heavier 
where they cross the posterior ridge ; posterior ridge moderate- 
ly developed, inclined to be double below, ending behind in a 
