258 ANNALS OF THE CARNEGIE MUSEUM. 
and no supra-anal is present. Inner lamina of inner gills free. Of the 
gills, only the outer ones are marsupial in the female, and the water- 
tubes in them are much closer than in the non-marsupial gills. Glo- 
chidia unknown. 
Type R. tuberculata (Rafinesque). 
This genus is more primitive than any of the foregoing because of 
the absence of a supra-anal opening. In the structure of the mar- 
supium it is a little more advanced, and is related to the following 
genera. In the characters of the shell it is rather peculiar, but re- 
minds somewhat of certain types of Quadrula. We can do justice 
to these conflicting characteristics only by recognizing this as a valid 
genus. 
Rotundaria tuberculata (Rafinesque). 
Three males and three females from the Ohio drainage in western 
Pennsylvania, and one female from the Ohio River at St. Marys, 
Pleasants Co., West Virginia, all collected by myself, have]been 
investigated. 
o=mp 
Fic. 7. Rotundaria tuberculata (Rafinesque). Sterile female, from Allegheny River, 
Kelly, Armstrong Co., Pa. (Carn. Mus., No. 61, 4,562.) Coll. July 25, 1910. 
The soft parts have been described by Simpson (in Baker, 1898, 
p. 86), but very poorly. 
Although there are only a few specimens at my disposal, the char- 
acters given for the genus are uniformly found in all of them. The 
most marked character is the absence of a supra-anal. Since Simpson 
