ORTMANN: FAMILIES AND GENERA OF NAJADES. 249 
anda female from Ouachita River, Arkadelphia, Clark Co., Arkansas. 
None of the females was gravid. 
The description of the soft parts given by Lea (Obs., X, 1863, p. 436) 
is incomplete. 
The anal opening is separated from the supra-anal by a moderately 
long connection of the margins of the mantle, which varies slightly, 
and is a little longer than the anal, but always much shorter than the 
supra-anal. In two cases this connection was absent. Branchial 
with well developed papilla, anal with minute papilla. Inner lamina 
of inner gills free, except at the anterior end. Posterior margins of 
palpi connected for about one-half of their length. 
Fic. 5a. Left gills of a sterile female of C. trapezoides, from Pearl River, Jackson, 
Hinds Co., Miss. (Carn. Mus., No. 61, 4,924.) 
Septa of the gills of the male rather distant from each other, and 
water-tubes wide. In the female the septa are much more crowded, 
and the water-tubes are narrow, chiefly so in the outer gill. In the 
inner gill of the female, near the base, the septa are a little more distant, 
but toward the edge they become more crowded by intercalation of 
additional ones, so that in the marginal half of this gill the water- 
tubes are almost as narrow as those of the outer gill. Altogether the 
marsupial character of the crowded septa is not so distinctly pro- 
nounced in the inner gill, although all four gills are built to receive 
eggs and to serve as marsupia, a fact, which is evidenced by the struc- 
