804 -PLEUROBEMA 
Unio estabrookianus LEA, Pr. Am. Phil. Soc., [V, 1845, p. 164; 
Tr. Am. Phil. Soc, X;°1853;:p2 77, pl. vy) Ge. 17; Obs iy; 
1848, p. 51, pl. v1, fig. 17- 
Margaron (Unio) estabrookianus Lea, Syn., 1852, p. 24; 1870, 
P- 35: 
Unio estabrokianus Pare, Conch. Sam., III, 1890, p. 152. 
Pleurobema estabrookiana SIMPSON, Syn., 1900, p. 763. 
Unio striatissimus ANTHONY, Am. Jl. Conch., I, 1865, p. 156, 
pl. xu, fig. 1—Sowersy, Conch. Icon., XVI, 1868, pl. 
LXXXVI, fig. 460. 
Strongly concentrically sculptured and not very inequilateral. 
The hinge plate is wide and flat; the muscle scars are deeper 
than in any of the allied forms. 
PLEUROPREMA SUBPLANUM (Conrad). 
Shell decidedly rhomboid, compressed or subcompressed,. 
somewhat inequilateral, rounded in front and slightly cut away 
below; base line almost straight; dorsal slope subtruncate ; 
posterior ridge full, rounded but disposed to be double below, 
ending in a narrow, feeble biangulation at the base of the shell ; 
beaks high, only moderately full, their sculpture a few strong 
ridges, which are heavier and turned up decidedly behind;. 
surface with irregular incremental striz; epidermis dirty 
greenish, sometimes feebly rayed; left valve with two strong, 
ragged pseudocardinals and two short, straight laterals; right 
valve with one pseudocardinal and one double lateral; beak 
cavities not deep, compressed; nacre whitish, thinner and. 
slightly iridescent behind. 
Length 45, height 30, diam. 16 mm. 
North Carolina and Virginia. 
Type locality, Branch of James River, Lexington, Rock-- 
bridge Co., Va. 
Unio subplanus Conran, Monog., IX, 1837, p. 73, pl. xi, fig. 
1.—Han ey, Biv. Shells Supp., 1856, p. 383, pl. xx1, fig. 16. 
—Kuster, Conch: Cab. Unio, 1862, p. 272. pl. xc fe. 5 — 
SIMPSON, Syn., 1900, p. 720. 
Margaron (Unio) subplanus Lea, Syn., 1852, p. 33; 1870, p- 
54- 
