862 QUADRULA 
obsolete ; posterior slope wide and somewhat elevated ; epider- 
mis smooth, light brown, sometimes inclining to orange, two 
or three concentric bands of green or black mark the earlier 
lines of growth. ‘Teeth of the left valve double, anterior car- 
dinal high, thin and wedge-shaped, the posterior cardinal tri- 
angular, low and small; laterals thin, rather short and nearly 
straight. In the right valve, the cardinals are divided by a 
deep cleft, extending nearly to the bottom of the anterior ad- 
ductor scar, the posterior tooth being much the smaller. The 
dorsal plate is quite wide for so small a shell. The shell cavity 
is quite capacious: the beak cavities deep and compressed. 
Nacre white, with brown splotches and very iridescent. The 
nacre is probably also salmon-colored in some individuals. The 
pallial line in the specimens before me is nearly imperceptibe 
in the posterior part of the shell, where the nacre is very thin. 
One specimen shows in the upper part of the shell cavity, 20 
or 30 almost microscopic muscle scars extending from the beak 
cavities half way to the pallial line. 
Long. 34, alt. 28, diam. 14 mm.” (Frierson). 
‘Type locality, Tallapoosa River, Tallahassee, Ala. 
Ouadrula archeri Frierson, Naut., XIX, 1905, p. 13, pl. 1 
HES jhe 2: 
“This shell is not closely allied to any shell, with which I am 
acquainted. On the one hand, it resembles some of the Pleu- 
robemas of the group typified by P. fassinans Lea and, on the 
other hand, it bears some resemblance to a young and thin Q. 
aurea Lea. In the concentric coloring of the lines of growth, 
it reminds one of O. asperata Lea. Its deep and compressed 
beak cavities place it in the genus Quadrula, while its resem- 
blance to the latter two species is too slight to cause any error 
in their direction.” 
QUADRULA PAUPERCULA (Lea). 
Shell subquadrate, a little narrower in front, subinflated, 
rather solid, slightly inequilateral; beaks probably full and 
high; posterior ridge full, angled, ending at the hinder base 
in a blunt point; anterior end round; base curved; posterior 
end with a somewhat curved, square truncation ; surface near- 
