256 Annals of the Carnegie Museum. 



phragm normal. Inner lamina of inner gills free from abdominal 

 sac, except at anterior end. 



Septa and water-tubes well developed. In the female all four gills 

 are marsupial, and possess the typical structure. In the basal portion 

 of the inner the water-tubes are somewhat wider, but there is hardly 

 any difference in their width in the marginal part of the two gills, 

 since the water-tubes of the inner gills become narrower by inter- 

 calation of additional ones. In the gravid female the gills swell 

 moderately, but their edges remain sharp. The eggs form only poorly 

 developed placenta? in the ovisacs, and the shape of the latter is com- 

 pressed and lanceolate (leaf-like). 



The eggs are whitish. I have not seen glochidia, but according to 

 Lefevre and Curtis (1910, p. 97, fig. E) they are normal in shape and 

 size. Length 0.18; height 0.19 mm. 



Color of soft parts whitish. As usual, the edge of the mantle, 

 chiefly along the posterior part, is more or less blackish or brownish. 

 Gills paler or darker grayish or brownish white. Foot brownish 

 white. The posterior part of the abdominal sac is often suffused with 

 black. 



Quadrula sparsa (Lea). 



One male and one sterile female, from the Cumberland River in 

 Cumberland and Pulaski Counties, Kentucky, at hand, received from 

 B. Walker. 



Identical in every detail with Q. metanevra, to which it is also allied 

 by the shell. The agreement extends so far, that minor details are 

 also identical, as the smooth edge of the anal, the shape of the palpi, 

 and the black pigment of the posterior part of the abdominal sac. 



In the male supra-anal and anal were not separated, but this region 

 was somewhat injured, so that the mantle-connection may have been 

 torn. 



Charged marsupia and glochidia unknown. 



Quadrula cylindrica (Say). 



Nine specimens (males and females) from the Ohio drainage of 

 western Pennsylvania have been examined in the laboratory, and 

 several more in the field, taken from the Ohio River in western Penn- 

 sylvania and Ohio. Two males were received from H. E. Wheeler, 



from the Ouachita in Arkansas. 



