680 UNIO 
Unio perlatus Lea, Pr. Ac. N. Sci. Phila., VII, 1863, p. 193: 
Jl. Ae. N. SerPhilas Vi; 1866; 9158 pli ive fea Obs: 
XG 16673 p.21G; plaiv. ies 122 
Margaron (Unio) perlatus Lea, Syn., 1870, p. 60. 
A delicate, compressed form, whose surface is finely, con- 
centrically striate. U. gracilentus is a little darker, but I do 
not think it 1s specifically or even varietally different. 
UNIO NAVICULOIDES Lea. 
Shell much elongated, subrhomboid, thin, convex, inequi- 
lateral; anterior end subtruncated above; base line straight or 
a little incurved in the middle; posterior ridge full, double, 
the lower ridge the stronger, ending behind in a biangulation 
below the median line; beaks apparently low and compressed: 
surface distinctly, though not strongly, marked with concen- 
tric sculpture ; epidermis dull olive-green, rather dark, scarcely 
shining ; pseudocardinals small, nearly smooth, one in the right 
valve and two in the left; laterals long, delicate and straight ; 
muscle scars small and shallow; nacre dull purplish, iridescent 
behind, 
Length 75, height 32, diam. 18 mm. 
Length 71, height 31, diam. 19 mm. 
Length 72, height 33, diam. 21 mm. 
Georgia. 
Type locality, Buckhead Creek, Burke Co. and Macon, Ga. 
Unio naviculoides Lea, Pr. Ac. N. Sci. Phila., IX, 1857, p. 170; 
Jls Acs N. Seis Phila, 1V, 1858.19) 94, pl. <x-hies 74 Obs 
VI, 1858, p. o4, pl. xx, fig. 74.—Simpson, Syn., 1900, p. 732. 
Margaron (Unio) naviculoides Lea, Syn., 1870, p. 60. 
Darker colored, more elongated, more decidedly sulcate and 
having a stronger posterior ridge than U. burkensis, but 
doubtfully distinct. I have seen only a limited amount of 
material of the two forms that I can consider valid. 
UnN1I0 sorpipus Lea. 
Shell subrhomboid, subelliptical or subovate, convex, sub- 
solid, inequilateral; beaks rather full and elevated above the 
dorsal line, their sculpture unknown; posterior ridge full, in- 
