254 ANNALS OF THE CARNEGIE MUSEUM. 
Quadrula tuberculata (Barnes). 
Fifteen specimens have been investigated, collected by myself in 
the Ohio drainage in western Pennsylvania; nine more have been re- 
ceived from H. E. Wheeler from the Tennessee drainage in northern 
Alabama, and the Ouachita River in Arkansas. Females are among 
them, but not in the gravid condition. 
Simpson has created for this species the genus Tritogonia, which he 
removed far from Quadrula. The shape of the shell is indeed somewhat 
strange at the first glance, but it is possible, without much difficulty, 
to correlate shape and sculpture with that of such species as Jachrymosa, 
aspera, and chiefly with certain southern forms, which probably also 
belong here (forshei Lea, speciosa Lea, apiculata Say). 
In the structure of the soft parts, this species is essentially a Quad- 
rula. The anal opening is separated from the supra-anal by a rather 
short mantle-connection; the latter was found absent in one case only 
(out of twenty-four). Branchial with well developed papille, anal 
with fine, but distinct crenulations, which sometimes resemble fine 
papillae. Inner lamina of inner gills free from abdominal sac, except 
at its anterior end. Posterior margins of palpi connected for one-half, 
or even more, of their length. 
Gills rather long, but also rather wide; their anterior attachment as 
usual. Septa well developed, rather distant from each other in the 
male. In the female they are more crowded in all four gills, and the 
water-tubes are narrow, but there is a slight difference between the 
inner and outer gill, the water-tubes of the former being slightly wider 
near the base of the gills. In the marginal portion there is hardly any 
difference in the water-tubes of the two gills (see Ortmann, 19110, 
pl. 86, fig. 4). In all four gills the septa are distinctly marsupial in 
structure: they are heavy, and have a folded epithelium. 
No gravid females have been seen by the writer, and the glochidia 
are still unknown. 
The color of the soft parts is grayish or yellowish (or brownish) 
white. 
Simpson (1900), p. 608) says of his genus Tritogonia: ‘‘in the female 
there is a thickened flap of the mantle which fills the circular posterior 
expansion of the shell, and which has a small flap inside.’”’ I have 
never seen anything answering to this phrase in my specimens. The 
chief expansion of the shell is at the anal opening, and the margin of 
this opening corresponds to it, and thus the anal is larger in the female, 
