620 UNIO 
base in a biangulation; anterior end slightly narrowed; pos- 
terior slope often wrinkled, obliquely truncated; surface with 
irregular growth lines; epidermis dirty, tawny-brown, some- 
times feebly rayed: left valve with two ragged, stumpy pseu- 
docardinals and two laterals, the lower largest; right valve 
with one pseudocardinal, sometimes with a small one above, 
and one lateral; muscle scars well marked; nacre lurid, tinted 
with purple. 
Length 59, height 39, diam. 22 mm. 
Type locality, Catawba River, North Carolina. Also, Flor- 
ida. 
Umio dorsatus Lea, Pr. Ac. N. Sci. Phila., XII, 1868, p. 160; 
ji. Ac. N. Ser Phila; VI, 1868; pc 300, pl. xnvitie. 1127 Ops. 
XIT, 1860, p. 60, pl. xiv, fig. 112.—Simpson, Pr. U. S. Nat. 
Mus., XV, 1892,\p. 411, pleaay fig. 75 11, hes; n; 2 Sy 
TQOO, p. ZIT. 
Margaron (Unio) dorsatus Lea, Syn., 1870, p. 37. 
This species shows relationships with the complanatus group. 
Some specimens recall U. congareus, but the shells are shorter, 
rougher and rather more narrowed in front. 
UNIO WACCAMAWENSIS Lea. 
Shell rather elongated, rhomboid, inequilateral, scarcely sub- 
solid, subinflated or inflated; beaks not high or full, their 
sculpture not seen; posterior ridge very high, decidedly an- 
gled, ending behind in a point at or near the base of the shell; 
dorsal slope obliquely truncate, the termination joining the dor- 
sal line at an angle; surface with delicate growth lines; pos- 
terior slope often wrinkled; epidermis ashy or smoky-green. 
with radiating wrinkles; left valve with two compressed pseu- 
docardinals and two delicate laterals; right valve with one 
pseudocardinal and one lateral; nacre bluish-white. 
Length 43, height 21, diam. 17 mm. 
Length 37, height 18, diam. 15 mm. 
Type locality, Waccamaw Lake, North Carolina. 
Unio waccamawensis Lea, Pr. Ac. N. Sci. Phila., VII, 1863, 
p. 193 [i Ac N. Sci. Philay: Vi;1866, p..lompion, ne. Ee; 
Obs., XI, p. 20, pl. v, fig. 14.—Simpson, Syn., 1900, p. 7II. 
Margaron (Unio) waccamawensis Lea, Syn., 1870, p. 36. 
