ORTMANN: FAMILIES AND GENERA OF NAJADES. Se} 
Obovaria circulus (Lea).* 
About a dozen specimens from the Ohio drainage of western Penn- 
sylvania have been investigated, among them gravid females. Several 
additional specimens were examined from the Ohio River in Ohio. 
Gravid females were found in the month of September, and on May 27, 
In the latter case, discharging individuals were secured, with holes 
in the edge of the marsupium. 
Structure of soft parts essentially the same as in O. retusa. In the 
sterile female, the ovisacs are slightly narrower than the regular water- 
tubes. Number of ovisacs up to thirty and more. As in the pre- 
ceding species the edge of the mantle in front of the branchial is in the 
female slightly lamellar and crenulated, but has only a brown (not 
blackish) mark along it. 
Glochidia (see Ortmann, 19110, pl. 89, fig. 15) similar to those of 
O. retusa, but smaller. Length 0.20; height 0.23 mm. 
Obovaria unicolor (Lea). 
I have received from A. A. Hinkley three males and eight gravid 
females, taken from the Pearl River, Jackson, Hinds Co., Mississippi, 
on Nov. 5, 1910. This species agrees in every particular with O. cir- 
culus, except that the glochidia are smaller. Length 0.16; height 
0.21 mm. (see Plate XIX, fig. 10). 
Obovaria (Pseudo6n) ellipsis (Lea). 
Two females were collected in the Ohio River in Beaver Co., Penn- 
sylvania, on August 29, 1908, one sterile, the other just beginning to 
fill the marsupium with eggs. Three males, one sterile, and six gravid 
females were secured in September, 1910, in the Ohio River in Ohio. 
Thus the beginning of the breeding season is normal. 
The soft parts are much like those of the other species of the genus. 
Anal and supra-anal separated for a short diatance. Anal crenulated, 
branchial with papilla. In front of the branchial the inner edge of the 
mantle of the female is slightly lamelliform, with fine crenulations. 
This part does not reach to’the middle of the lower margin, and farther 
in front the edge is smooth. Posterior margins of palpi connected 
only at base. Inner lamina of inner gills connected with abdominal 
sac. 
43 This includes O. lens (Lea), which is not specifically distinct. 
