QUADRULA 857 
This species is associated with Q. pustulosa and is often 
mistaken for it. It has as a rule smoother epidermis, much 
fewer and larger tubercles, which are inclined to be placed 
in two radial rows. ‘There are occasional specimens, which are 
nearly or quite destitute of pustules. Occasionally this species 
has a few small nodules on the dorsal slope. ‘The truncation 
of the posterior end is strong and, as in some of the species 
of this group, the upper part of the truncation often overhangs 
the lower part. 
QUADRULA NODIFERA (Conrad). 
Shell subquadrate or subrhomboid, inflated, moderately solid, 
somewhat inequilateral; beaks full and high; anterior end 
rounded, usually a little narrowed; base line curved in front, 
straight behind; posterior end rounded from the beaks to the 
lower end of the posterior ridge; posterior ridge moderately 
developed, subangular, ending in front of the extreme poste- 
rior end of the shell; surface smooth or having a few scattered 
nodules; epidermis dull, dirty or grayish-brown; pseudocar- 
dinals triangular, much split up into radial denticles; lateral 
of the right valve double or single; beak cavities rather deep ; 
muscle scars small, impressed; nacre white or lurid, often 
blotched. 
Length 47, height 39, diam. 27 mm. 
Length 44, height 34, diam. 27 mm. 
Louisiana and eastern Texas. 
Type locality, Jackson, La. 
Unio nodiferus Conran, Pr. Ac. N. Sci. Phila., I, 1841, p. 19; 
(i owc Ne Sey Phila. Ie tsco: p.. 277, pl. xxxvii,.fies..4, 8. 
Quadrula nodifera Stimpson, Syn., 1900, p. 782. 
A somewhat doubtful species. I have seen no specimens, 
which exactly agree with the figure of the species as given 
by Conrad. Is is usually a little narrowed in front and the 
outline of the posterior end sweeps around in an almost regular 
curve from the beaks to a point on the base considerably in 
front of the extreme hinder part of the shell. It is rarely 
raised into a low angle behind the ligament. 
