QUADRULA 907 
nodulous generally throughout; epidermis yellowish-brown 
to ashy in young shells, darker in old shells; left valve with 
two rather high, subcompressed pseudocardinals, the anterior 
one elongated, and there is an indication of a low ragged tooth 
below and between them, with two nearly straight laterals, the 
lower larger; right valve with a ragged, solid, but somewhat 
compressed, pseudocardinal ; sometimes there is a second tooth 
above it and again it is wanting, and one lateral, which shows 
a tendency to split a little; beak cavities deep, compressed ; 
anterior scars ragged; posterior scars round and _ shallow; 
pallial line distant from the border; nacre pale purplish, sal- 
mon-rose or deep coppery. 
Length go, height 73, diam. 48 mm. 
Length 80, height 64, diam. 37 mm. 
Length 68, height 63, diam. 37 mm. 
Guatemala: Tabasco, Mexico. 
Unio ostreatus Moreier, Test. Noviss., 1849, p. 290.—FISCHER 
and Crosse, Miss. Sci., IJ, 1894, p. 573, pl. xi, fig. 3; LXx, 
fig. 4. 
Quadrula ostreata SImPpson, Syn., 1900, p. 796. 
Fischer and Crosse have figured a young, very high shell in 
the Mission Scientifique. As the species grows older it be- 
comes elongated and drawn down at the posterior base. ‘This 
is more triangular, more solid, and inflated than guadrata and 
is in every way a more robust shell. 
QUADRULA PROFUNDA N.. S. 
Shell irregularly triangular or trapezoidal, very inequilateral, 
solid in front and thinner behind, inflated, the umbonal region 
greatly elevated: beaks strongly turned inward and forward, 
but rather remote from each other, their sculpture not ob- 
served; lunule large, truncate in front, extending under the 
beaks; posterior ridge high, curved, angled with a faint ridge 
behind it and a shallow, wide radial furrow in front of it and 
ending at the base in a blunt point; post-dorsal line almost reg- 
ularly curved from the umbonal region to the posterior base; 
anterior outline in the form of an ogee, rounded below, in- 
curved sharply above to the overhanging beaks, base line in- 
