746 PLEUROREMA 
“, beautiful species, which is more brightly painted than 
cuneolus, and is more compressed behind laterally than that 
shell. It is brighter and less elongated than P. lesleyi. 
PLEUROBEMA ACUENS (lLea). 
Shell irregularly ovate or subrhomboid, subinflated, solid, 
inequilateral; beaks high and full, with a lunule in front of 
them ; anterior end rounded or very slightly subtruncate above ; 
base line evenly curved: outline of dorsal slope curved, high 
and almost angled behind the ligament; posterior ridge round- 
ed, ending behind above the base of the shell in a rounded 
point ; surface with uneven growth lines ; epidermis pale tawny, 
with a few broken, green rays, scarcely shining; pseudocardi- 
nals small, triangular, two in the left valve and one in the 
right ; two laterals in the left valve and a double one in the 
right; beak cavities shallow; muscle scars small, deep; nacre 
beautiful silvery, richly iridescent and thinner behind. 
Length 33, height 25, diam. 16 mm. 
Tennessee River system. 
Type locality, Holston River, Concord, Tenn. 
Unio acuens Wek, Pr-Ac. Nat; Sci. Phila.” 1871. p: 19o0seyL- 
Ae. Nata semjbhila. VI 1874 sp.27,.pl. vin, te 24 Oras 
XT, 1674. si pl Winn, no eae 
Pleurobema acuens SIMPSON, Syn., 1900, p. 479. 
Apparently this is a rare shell and all the specimens I have 
seen are small, though they have the appearance of being adult. 
It is a neat species, the posterior ridge being widely rounded, 
the greatest degree of inflation being above it. The nacre is 
beautifully soft and rich, and it has the faintest hint of red. 
The hinder part is richly iridescent and almost coppery and it 
is much thinner than the rest of it. 
PLEUROBEMA ORNATUM (Lea). 
Shell subrhomboid, subcompressed, solid, inequilateral ; 
beaks high, only moderately full, their sculpture apparently a 
few coarse ridges; lunule small; posterior ridge rounded, end- 
ing behind in a rounded point near the base of the shell; base 
