894 QUADRULA 
base line rounded to almost straight; outline of dorsal slope 
curved, sometimes elevated just behind the ligament ; posterior 
ridge moderate, rounded; greatest diameter of the shell just 
below the beaks , surface covered with rude, concentric growth 
lines; epidermis concentrically wrinkled, of various shades of 
dull brown or greenish-brown with faint, broken rays when 
young; pseudocardinals triangular, radially striate; lateral of 
the right valve inclined to be double; muscle scars small, im- 
pressed ; beak cavities decidedly deep, compressed ; nacre whit- 
ish, often blotched, thinner and brownish or bronzy, iridescent 
behind. 
Length 66, height 51, diam. 31 mm. 
Tength 50, height 45, diam. 27 mm. 
Tennessee and Cumberland River systems; Green River, 
Kentucky ; reported from the Ohio River. 
Type locality, French Broad and Holston Rivers, Tenn. 
Unio polaris Lea, Pr. Am. Phil. Soc., I, 1840, p. 285; Tr. Am. 
Phil. Soc., VIIT, 1842, p. 209, pl. x1v, fig. 24; Obs., III, 1842, 
p. 47, pl. xiv, fig. 24.—Cuenu, Ill. Conch., 1858, pl. xxix, 
figs. 3, 3a, 3b.—Kuster, Conch. Cab., 1861, p. 255, pl 
LXXXVI, fig. 3—Rreve, Conch. Icon., XVI, 1865, pl. xxvit, 
fig. 138. 
Margaron (Unio) pilaris Lea, Syn., 1852, p. 35; 1870, p. 56. 
Quadrula pilaris SIMPSON, Syn., 1900, p,. 792. 
Umio lesueurianus Lea, Pr. Am. Phil..Soc., I, 1840, p. 286; 
Tr. Am. Phil. Soc., VIII, 1842, p. 195, pl. vu, fig. 6; Obs., 
III, 1842, p. 33, pl. vin, fig. 6—CueEnu, Ill. Conch., 1858, 
pl. xxx, figs. 4, 4a, 4b.—Kustrr, Conch. Cab. Unio, 1861, 
Pp. 215, pl. xccm, he. 2: 
Margaron (Unio) lesuerianus LeA, Syn., 1852, p. 353 1870, p. 
56. 
Closest, perhaps. to Q. subrotunda. It is a smaller species, 
the young shell is more evenly curved on the dorsal slope, and 
the beaks are hardly so high. The posterior part of the nacre 
is usually darker. 
