QUADRULA 893 
muscle scars impressed; beak cavities rather deep, compress- 
ed: nacre white, porcellaneous, thinner and slightly iridescent 
_ behind. 
Length &9, height 65, diam. 44 mm. 
Length 74, height 65, diam. 38 m. 
Length 68, height 46, diam. 30 mm. 
Ohio, Cumberland, and Tennessee River systems. Reported 
from Michigan and the Grand River, Ontario, but it is prob- 
able that the material from these localities is not subrotunda. 
‘Type locality, Ohio. 
Unio subrotundus Lea, Tr. Am. Phil. Soc., IV, 1831, p. 117, 
pl. xvi, fig. 45; Obs., I, 1834, p. 127, pl. xviu, fig. 45.— 
HAN LEY, Biv. Shells, 1843, p. 203, pl. xx, fig. 58. ?>CHENU, 
Ill. Conch., 1858, pl. xv, figs. 1, 1a, 1b—Kuster, Conch. 
Cab.,,font; p. 190, pl. LX, ne. 3. 
Margarita (Unio) subrotundus Lea, Syn., 1836, p. 343; 1838, p. 
22: 
Margaron (Unio) subrotundus Lua, Syn., 1852, p. 35 ; 1870, p. 
50. 
Quadrula subrotunda Stimpson, Syn., 1900, p. 791. 
Fusconaja subrotunda ORtTMANN, Ann. Car. Mus., VIII, 1912, 
p. 244. 
?Umio brevialis CRoucH, Ill. Int. to Lamarck, 1827, p. 16, pl. 
ix, Hie. 3. 
Unio personatus Conrav, New F. W. Shells, 1834, p. 71. 
Unio politus Say, Am. Conch., VI, 1834.—Conrap, Monog., 
VIII, 1837, p. 67, pl. xxxvil, fig. 2—Kuster, Conch. Cab. 
Unio, 1852, p. 62, pl. x1v, fig. 4.—Sowerrsy, Conch. Icon., 
XVI, 1866, pl. xxx, p. 168. 
It is very hard to draw a satisfactory line between this and 
QO. kirtlandiana. Both have the same scheme of coloring, but 
the latter is generally larger, more compressed and has lower 
beaks. 
QUADRULA PILARIS (Lea). 
Shell irregularly short oval, inflated, solid, inequilateral ; 
beaks rather high and full, turned forward over a lunule; 
anterior end generally lightly truncated above, rounded below ; 
