1668 UNIO 
A large, elongated, compressed form, which approaches 
hopetonensts, but is less inflated and less rhomboid than that 
species and has a duller nacre. The young shells of this spe- 
cies never have that peculiar olive-green tint found on the 
young of hopetonensis. 
Var. northamptonensis Lea. 
Shell subelliptical or subovate, rather long, compressed, the 
biangulation often a little higher up than in the type ; epidermis 
tawny or tawny-greenish, generally rayed in old ones; nacre 
whitish or dirty purplish. 
Length 110, height 58, diam. 24 mm. 
Type locality, Connecticut River at Northampton, Spring- 
field and below Hartford, Mass.; Neuse River, N. C. 
Unio northamptonensis ma, Pr. Ac. N. Sci. Phila., V, 1861, 
p.. 3902; Jl. Ac: N.-Sci: Philas- Ve1S62) p90. pla cyano 
260 ;Obs:, LX, 1863.-p: 12; ply xxv nties 2ae: 
Margaron (Unio) northamptonensis Lea, Syn., 1870, p. 51. 
Unio roanokensis var. northamptonensis SIMPSON, Syn., 1900, 
pu 728: 
This agrees so closely with specimens of roanokensis that | 
have been induced to consider it as a variety of that, notwith- 
standing its widely separated distribution. I have before me 
roanokensis from the Savannah River, named by Dr. Lea and 
belonging in his collection, that agree in all essential characters 
with sxorthamptonensis from the type locality. Both have the 
same general form, the inflation behind, the middle of the base 
and the same color within and without. The variety has the 
same low, ill-defined, strongly cross-striated pseudocardinals 
as the type. 
UNIO HOPETONENSIS Lea. 
Shell rather large, subrhomboid, a little narrowed in front, 
subcompressed to subinflated, the greatest diameter being at 
the posterior ridge, in front of which the shell is wedge-shaped ; 
posterior ridge well developed, single and narrowly rounded 
above, double below, ending in a wide biangulation at or above 
