736 PILEUROBEMA 
running close to the dorsal line; near the ante-ior end there 
is a wide, radial inflation extending from the beaks and fading 
out below and the greatest diameter of the shell is at this in- 
flation; growth lines rude and uneven; epidermis yellowish- 
green, greenish-yellow, tawny, or brownish, usually more or 
less decorated with bright green rays; the rays often coalesce 
and are broken until they appear as square blotches, some- 
times they are narrow and broken, smooth and shining to 
rough and dull; pseudocardinals variable; there are generally 
two in the left valve, the posterior stronger, often united above, 
solid, rough, radial or the upper running nearly parallel with 
the dorsal line; right valve with a strong pseudocardinal, there 
is often one above it and another in front of it; laterals two 
in the left valve and a double one in the right, heavy and gran- 
lar; beak cavities shallow; muscle scars small, deep; nacre 
silvery white, thicker in front. 
Length 80, height 50, diam. 35 mm. 
Length 87, height 47, diam. 37 min. 
Length 58, height 39, diam. 33 mm. 
Ohio, Cumberland, and Tennessee River systems, Maumee 
Basin, Western New York, Ottawa, Canada (Call). Reported 
from Iowa City, lowa; St. Peter’s River, Minnesota, and from 
Nebraska. 
Type locality, Lake Erie. 
Unio clava LAMARCK, An. sans Vert., VI, 1819, p. 74.—Con- 
RAD, Monog., I, 1835, p. 5, pl. 1, fig. 1—Kustrer, Conch. 
Cab. Unio, 1852, p. 39, pl. vu, fig. 2—Sowersy, Conch. 
Icon., XVI, 1868, pl. Lxrx, fig. 354. 
Pleurobema clava Acassiz, Arch. fur Naturg., I, 1852, p. 49.— 
SIMPSON, Syn., 1900, p. 745.—ORTMANN, Ann. Car. Mus. 
VIII, 1912, p. 264. figs. 9-9a. 
Unio clavus Reeve, Conch. Syst., I, 1841, p. 117, pl. LXXxXvIII, 
fig. 3—Han ey, Biv. Shells, 1843, p. 187, pl. xx, fig. 52— 
Cann, TreAcad Sci. Storms, Vil 18952 Wor te pso, pleu 
Margarita (Unio) clavus Laas, Syn., 1836, p. 22; 1838, p. 18. 
Margaron (Unio) clazus Lea, Syn., 1852, p. 26; 1870, p. 40. 
