ORTMANN: monograph of the naiades of PENNSYLVANIA. 9 



soft parts are entirely different, and, when females are at hand, there is no mistake 

 possible. The soft parts of F. subrotunda are often of the orange type, of Pleurobema 

 obliquum never. Specimens with red nacre are always obliquum-ioTms, and never 

 siibrotunda. 



There is no difference whatever between the sexes in the shell of this species. 

 The differences between it and var. kirtlandiana will be discussed under the latter. 



Much confusion prevails as to this species, and it has often been misidentified, 

 probably because originally only the young was described, and no good figures of 

 the old shell were published. The synonymy given b}' Simpson seems to be 

 correct, but I think that the following reference should be added: Unio varicosus 

 Lea (Obs. I, 1834, pi. 11, fig. 20, Ohio River). Lea compares this with Plethobasus 

 cyphyus (= cesopus), and Simpson (1900, p. 765) identifies it with Plethobasus 

 cicatricosus (Say). Lea's figure would stand very well for an old Fusconaia sub- 

 rotunda, except for its color, which is too light, but I have several old specimens 

 with a rather light (brown) epidermis, although not as light as in this figure. The 

 color of Lea's varicosus is all that agrees with Pleurobema cicatricosus. According 

 to specimens of the latter in the Carnegie Museum, and the figures of Reeve (1864, 

 PL 8, fig. 31, and PI. 13, fig. 50), the character of the concentric ridges of the shell 

 is entirely different from that in Lea's figure. Furthermore the shape of the 

 latter is not at all the characteristic shape of cicatricosus. The specific name 

 varicosus would have priority (1829) over subrotundus, but cannot be used, since 

 it is pre-occupied by U. varicosus Lamarck, 1819, now Alasmidonta varicosa. 

 Localities in Pennsylvania, represented in the Carnegie Museum: 



Ohio River, Cooks Ferry, Shippiugport, Industry, Beaver Co.; Coraopolis (S. N. Rhoads) and Neville 

 Island, Allegheny Co. 



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



Mahoning River, Mahoningtown, Lawrence Co. 



Allegheny River, Aladdin, Godfrey, Johnetta, Kelly, Armstrong Co. 



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

 mann). 



Cheat River, Cheat Haven, Fayette Co. 



Other localities, represented in the Carnegie Museum. 



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

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



Tuscarawas River, Ohio (Holland collection). 



Levisa Fork of Big Sandy River, Prcstonsburg, Floyd Co., Kentucky.'" 



Tennessee River, Florence, Lauderdale Co., Alabama (H. H. Smitii)-" 



■° Only one specimen found by myself. It has the diameter of fifty percent, and thus belongs here, 

 but stands close to the var. kirtlandiana. 



"These specimeiis do not differ from the general run of the form from the Ohio. In tin; uiiper 



