QUADRULA 853 
Margaron (Unio) cooperianus Lia, Syn., 1852, p. 22; 1870, p. 
34. 
Quadrula cooperiana Simpson, Syn., 1900, p. 781. 
Plethobasus cooperianus ORTMANN, Ann. Car. Mus., VIII, 
1912, p,.. 267. 
Unio striatus Reeve, Conch. Icon., XVI, 1864, pl. vii, fig. 30. 
Usually somewhat triangular and always having very high 
beaks. It is occasionally nearly orbicular in outline. The 
epidermis is reddish-brown, the hinder two-thirds of the shell 
has very strong, irregular pustules. They are usually strong- 
est and longitudinally compressed from the umbonal region 
down towards the middle of the base. Very young shells are 
greenish-brown or brownish-green. 
Ortmann, (1. c.), states that “the anatomy of this species 1s 
practically identical with that of P. @sophus, agreeing in all 
particulars, chiefly so in the peculiar color of the soft parts.” 
QUADRULA MORTONI (Conrad). 
Shell subquadrate, inflated, subsolid, sometimes solid when 
old, inequilateral; beaks high and full, turned forward over 
a lunule; posterior ridge well developed, angled or narrowly 
rounded, rarely somewhat double below, ending at the base 
of the shell in a blunt point; anterior end rounded, sometimes 
slightly, obliquely truncate above; base line straight or lightly 
curved; outline of dorsal slope curbed or raised in the middle 
to an angle; surface varying from almost smooth to densely 
pustulous, pustules generally covering the whole shell; epi- 
dermis ashy-brown or lurid brown, having a greenish tint and 
sometimes a broad, broken, green ray when young; pseudo- 
cardinals triangular, not greatly split up; lateral of the right 
valve scarcely double; beak cavities deep, compressed ; muscle 
scars impressed ; nacre whitish with a purplish tint, purple and 
iridescent behind. 
Length 60, height 52, diam. 35 mm. 
Lower Mississippi river drainage as far north as western 
Tennessee and Indian Territory; west into eastern Texas. 
Type locality, Bayou Teche, La. 
