THE NAUTILUS. 139 



THE SYSTEMATIC POSITION OF THE UNIONID-GENUS PARSEYSIA. 



BY A. E. OKTMANN. 



In Nautilus, vol. 22, Feb. '09 p. 107, Frierson reports that in 

 Parreysia ?A\four gills serve as marsupium in the gravid female, a 

 character wliich does not agree with Simpson's definition of the sub- 

 family Hyriwce (Hyi-iavce). He concludes tiiat, in this instance, we 

 should not pay attention to the marsupial character, but should rely 

 upon the radial sculpture of the beaks of the shell. 



Recently I received a number of these Parreysias through the 

 courtesy of Mr. Frierson, and I am much obliged to him for giving 

 me the opportunity to examine them. I should call the species 

 Parreysia wynegungaensis (Lea) altliough a number among them 

 distinctly incline toward P. corrugata (Muell.) There are 30 of 

 them, 13 males, 11 sterile, and 6 gravid females; none of the latter 

 had glochidia, but only eggs in various stages of development. There 

 was no sex differentiation whatever in the shells. 



An examination of the soft parts revealed the fact, tliat not only 

 all four gills are marsupial in the female, but that the ivliole structure 

 of the soft parts is absolutely like the JS'orth American Quadrula (see : 

 Ortmann, in : Nautilus, 23, Feb. '10 p. 116). The only, and un- 

 important, differences are, tliat the svpraanal opening is rather 

 widely separated from the anal, and that the inner lamina of the 

 inner gill \s entirely connected with the abdominal sac. For the 

 rest, all other characters are like Quadrula, and the most prominent 

 features are the following. 



The inner edge of the anal opening is finely crenulated ; that of 

 the branchial opening is papillose, and rather well defined anteriorly; 

 in front of the latter, there are fine crenulations on the inner mantle- 

 edge for a short distance, but no special structures, such as papillae 

 or flaps. The gills are unequal, the outer considerably smaller than 

 the inner. The diaphragm is normal, and the outer lamella of the 

 outer gill is connected with the mantle to the posterior end. In the 

 male, there are well developed water tubes in the gills, but they are 

 rather wide, and the septa separating them are far apart. In both, 

 the male and female, the edge of the inner gill possesses a longitu- 

 dinal furrow, which is absent in the outer gill. In the female, all 

 four gills serve as marsupium^ and possess the structure of marsupial 

 gills ; the water tubes are narrow, and the septa are close together 



