QUADRULA 821 
Onio costatus CONRAD, Monog., II, 1836, p. 17, pl. vir.—Kus- 
TER, Conch. Cab., 1852, p. 54, pl. x1, fig. 4.—Rerrve, Conch. 
Icon., XVI,. 1864, pl. tv, fig. 16. 
Plectomerus costatus Conrap, Pr. Acad. N. Sci. Phila., VI 
1853, p. 260. 
Unio plicatus Kuster, Conch. Cab., 1856, p. 137, pl. x1, fig. 3. 
—CueEnv, Manual, 1859, IJ, p. 143, fig. 706. 
Unio atrocostatus Sowrersy. Conch. Icon., XVI, 1868, pl. 
LXXvVII, fig. 404. 
Var. latecostata (lea). 
This is possibly worthy of a varietal designation. It is gen- 
erally not quite so solid as the tvpical form and the oblique 
folds are finer and more numerous. 
Length 135, height 85, diam. 50 mm. 
Type locality, Tuscaloosa, Alabama. Also, Illinois; Mis- 
souri: south to Texas. 
Unioriatecosiatus ma, Pr. Am. Phil. Soc., 1V, 1845;. p. 1633 
ime. Philo Soc. ©, 1648,, p. 68, pl. 1, fig. 2; Obs., TV, 
1848, p. 42. pl. 1, fig. 2—Kusrer, Conch. Cab., 1861, p. 251, 
Pile Lx ety, fis. 4. 
Margaron (Unio) laticostasus Lea, Syn., 1852, p. 21. 
Margaron (Unio) laticostatus LEA, Syn., 1870, p. 31. 
Umio laticostatus H. and A. ApAMs, Gen. Rec. Moll., II, 1857, 
P. 497. 
Ouadrula undulata var. latecostata Stimpson, Syn., 1900, p. 
760. 
More delicate in every way than the type, but connecting 
with it. 
Var. pilsbryi (Marsh). 
Shell subrhomboid, slightly inflated and thickened before, 
compressed and thin behind; epidermis dark reddish-brown: 
plications small. seminodulous. 
Kansas. 
Type locality, Little Red River, Arkansas. 
