PILEUROBEMA 791 
the anterior and posterior ones feeble, and a double lateral ; 
beak cavities shallow; muscle scars small, impressed; nacre 
lurid purple; iridescent and thinner behind. 
Length 44, height 33, diam. 16 mm. 
Type locality, Tellico River, Monroe County, Tennessee. 
Also, East ‘Tennessee. 
Unio lenticularis Lma, Pr. Acad. N. Sci. Phila., II, 1872, p. 
i557 Jl Acad: N. Se: Phila, Vill, 1874, p: 30, pl. 1x, fig. 
27; Obs., XIII, 1874, p. 34, pl. 1x, fig. 27—Simpson, Syn., 
1900, p. 761. 
A very rare species. A small shell, which Lea has placed 
with this, is, I think, a P. barnesianum, and another is possibly 
a P. meredithti in bad condition. The species is close to the 
latter and may merge into it. The type is rather dark brown, 
and the nacre is a peculiar lurid purple tint. 
PLEUROBEMA MEREDITHI! (Lea). 
Shell subovate or subrhomboid, lenticular, subsolid, inequi- 
lateral; beaks little elevated or inflated; posterior ridge well 
developed, inclined to be narrowly double, ending below the 
median line in a feeble biangulation; anterior end round; base 
line curved; outline of dorsal slope curved, elevated just be- 
hind the ligament; surface with irregular, concentric sculp- 
ture; epidermis finely, concentrically wrinkled, greenish-yel- 
low or brownish, dull; left valve with two pseudocardinals and 
two curved laterals; right valve with one to three pseudocard1- 
nals and a double lateral; beak cavities not deep; muscle scars 
small, impressed; nacre silvery white or flesh-colored. 
Length 45, height 36, diam. 18 mm. 
Tennessee River system; Black Warrior River, Alabama. 
Type locality, Tennessee River, Tuscumbia, Ala. 
Unio meredithn Lea, Pr. Ac. N. Sci. Phila., II, 1858, p. 40; 
tieAcy Na Ses, (Phila. 7V , 1862, p: 65, ple vi, fig: 2145" Obs:, 
VIII, 1862; p. 69, pl. vi, fig. 214. 
Margaron (Unio) meredithti Lax, Syn., 1870, p. 35. 
Pleurobema meredithti Stimpson, Syn., 1900, p. 76. 
