840 QUADRULA 
Animal with all four gills used as a marsupium throughout, 
inner much the larger, free from the abdominal sac nearly or 
quite their whole length; palpi very large; branchial opening 
generally having clustered, often branching, papille; anal 
opening smooth; superanal opening closed below. 
(QUADRULA ASPERA (Lea). 
Shell subrhomboid, moderately inflated, subsolid to solid, 
somewhat inequilateral; beaks high, rather full, their sculpture 
a number of strong, somewhat double-looped ridges, which 
gradually blend into the sculpture of the surface; posterior 
ridge well-developed, distinctly double and angled, ending at 
the base oi the shell in a decided biangulation; in front of it 
there is a wide radial depression and there is often another be- 
hind it, the outline of the shell being incurved where these 
depressions end; anterior end rounded, slightly, obliquely trun- 
cate above; base line incurved in front of the posterior ridge; 
post-dorsal slope often curved, sometimes raised to an angle 
behind the ligament; surface more or less covered with coarse 
and fine pustules, which are often longitudinally compressed, 
they are frequently stronger in the anterior post-ridge and 
down the middle of the disk ; the depressed area between being 
smoother ; epidermis lurid greenish to brown, scarcely shining ; 
pseudocardinals radial, radially striate and often much split; 
laterals curved, that in the right valve somewhat double ; ante- 
rior scars deep, partly filled with rough nacre; beak cavities 
moderately deep; nacre whitish, iridescent behind. 
Length 63, height 50, diam. 30 mm. 
Length 7o, height 47, diam. 30 mm. 
Length 56, height 47, diam. 27 mm. 
Streams flowing into the Gulf of Mexico from Alabama 
west to central ‘l‘exas, and northward to the Verdigris river, 
Kansas. 
Type locality, Alabama river. 
Unio asper Lea, Tr. Am. Phil. Soc., IV, 1831, p. 85, pl. 1x, fig. 
15; Obs., I, 1834, p. 95, pl. rx, fig. 15.—HANLEy, Biv. Shells, 
1843, p. 179, pl. xxu, fig. 37—CuENu, Ill. Conch., 1858, pl. 
XV, figs. 4, 4a, 4b; Manual, 1859, II, p. 142, fig. 695.—REEvE, 
Conch. Icon. XVI, 1864, pl: vee 16. 
