ORTMANN: monograph of the naiades of PENNSYLVANIA. 35 



Soft parts (See Ortmann, 1912, p. 251). Glochtdia figured by Lefevre & Curtis 

 (1910, p. 97, fig. F, and 1912, p. 146, fig. F), 0.23 X 0.32 mm.; by Surber (1912, 

 PL 2, fig. 20) 0.23 X 0.29 mm., and by Howard (1914, PI. 5, fig. 36). I have seen 

 them in specimens from West Virginia and Arkansas, and found them to vary 

 somewhat in size: 0.21 X 0.26 mm. (Arkansas), and 0.22 X 0.29 mm. (West 

 Virginia) . They are rather large for the genus. 



Breeding season: Gravid females have never been observed in our state, but 

 I have them from Arkansas, collected on May 19, 1911, and July 19, 1913, and 

 from West Virginia, collected July 10, 1911. In the upper Tennessee region, I 

 found them on May 25, 1914. This is probably a summer breeder (tachytictic). 



Remarks: This species is well-distinguished by the general shape and sculp- 

 ture, although the latter is often poorly developed and even absent (chiefly in 

 young specimens). The sculpture always begins at a certain distance from the 

 beaks, and does not represent a continuation of the beak-sculpture. In its general 

 character, this sculpture resembles that of certain species of other genera, chiefly 

 of Plethobasus cooperianus (Lea), and there are cases, where it is hard to distinguish 

 these two species by the shell alone. However, P. cooperianus is generally more 

 oblique, and the nodules are rather distinctly confined to the posterior half of the 

 shell. Of course, they are easily told apart, when the soft parts are at hand. 



The shells from the Ohio-drainage in Pennsylvania are undoubtedly all tj'pical 

 Q. pustulosa. But outside of our state this species varies greatly, not only in 

 sculpture, but also in shape. These variations are in part geographical, and have 

 been named, but cannot be discussed here. 



Localities in Pennsylvania, represented in the Carnegie Museum: 



Ohio River, Shippingport, Cooks Ferry and Industry, Beaver Co.; Neville Island, Allegheny Co. 



Beaver River, AVampum, Lawrence Co. (G. H. Clapp & H. H. Smith). 



Mahoning River, jMahouingtown and Edinburg, Lawrence Co. 



Monongahela River, Westmoreland Co., and Charleroi, Washington Co. (G. A. Ehrmann). 



Cheat River, Cheat Haven, Fayette Co. 



Allegheny River, Natrona, Alleghenj' Co.; Godfrey and Kelly, Armstrong Co. 



Locality in Pennsylvania, represented in the Philadelphia Academy of Natural 

 Sciences: 



Ohio River, Coraopolis, Allegheny Co. (S. N. Rhoads). 



Other localities, represented in the Carnegie Museum: 



Ohio- Mississippi-drain age: 



Ohio River, Toronto, Jefferson Co., Oliio; St. !Marys, Pleasants Co., West Virginia; Parkersburg, Wood 

 Co., West Virginia; Portland, Meigs Co., Ohio; Portsmouth, Scioto Co., Ohio. 



Little Kanawha River, Grantsville, Calhoun Co, (F. W, Graham); BurnsyiUe, Braxton Co., West Vir- 

 ginia. 



