OV 
“NI 
Ce 
UNIO 
Unio dispalans B. H. Wricu'r, Naut. XIII, 1899, p. 50.— 
Simpson, Pr. Ac. N. Sci. Phila., 1900, p. 80, pl. 1, fig. 9; 
Syn., 1900, p. 736. 
A puzzling form which has no decided characters, yet which 
does not seem to equal anything else. Since seeing the type 
shell I have examined other material and rather incline towards 
placing it in the complanatius group. 
Unio ANGUSTATUS Lea. 
Shell elongated, subrhomboid or subelliptical, subcompressed 
to scarcely inflated, the greatest diameter being at the poste- 
rior ridge; thin to subsolid, inequilateral; beaks scarcely ele- 
vated or inflated, their sculpture being strong ridges running 
nearly parallel with the growth lines; posterior ridge well 
developed, angulated, more or less double, ending behind in 
a slight biangulation at or below the median line; surface 
with decided concentric sculpture; epidermis olive in young 
shells, nearly black in old ones, rather dull; pseudocardinals 
compressed, double in each valve, the upper one in the right 
valve small; laterals long, somewhat club-shaped ; muscle scars 
shallow ; nacre purplish-brown. 
Length 98, height 42, diam. 23 mm. 
Length 74, height 30, diam. 19 mm. 
South Carolina to western Georgia. 
Type locality, Cooper River, S$. C. 
Unio angustatus Lea, Tr. Am. Phil. Soc., IV, 1831, p. 114, pl. 
xvu, fig. 43 ; Obs., I, 1834, p. 124, pl. xvut, fig. 43 Conran, 
Monog., XI, 1838, p. 98, pl. Liv, fig. 2—HaAntEy, Biv. Shells, 
1843, p. 204, pl. xxu1, fig. 25 —CuEnu, Ill. Conch. 1858, pl. 
XIV, figs. 1, Ta, 1b.—Kuster, Conch. Cab. Unio; 1801)" p 
178, pl. Lv1, fig. 4.—Sowersy, Conch. Icon., XVI, 1868, pl. 
LXXII, fig. 372.—SIMPpsON, Syn., 1900, p. 731. 
Margarita (Unio) angustatus Les, Syn., 1836, p. 35; 1838, p- 
23. 
Margaron (Unio) angustatus Lea, Syn., 1852, p. 36; 1870, p. 
cs 
We 
