ORTMANN: monograph of the naiades of PENNSYLVANIA. 333 



tinguished from T. rangiana by the presence of a radial row of tubercles upon the 

 middle of the shell, standing in the male upon the radial rib, in the female in front 

 of the marsupial expansion; and further T. torulosa has the postbasal expansion 

 of the female dark green in color. 



Slightly tubcrculate specimens once existed in Pennsylvania, and I collected 

 such in an Indian Garbage heap at Point Marion (Ortmann, 1909c). I have 

 called them T. cincinnatiensis, but they are not the true cincinnatiensis, and are 

 by no means the typical T. torulosa. Whether forms approaching the latter once 

 existed in the Monongahela and Ohio cannot be now ascertained. All living 

 shells from Pennsylvania are typical rangiana. Some specimens, indeed, show 

 indications of tubercles, but these are rather indefinite, obscure swellings, the 

 majority of the specimens being perfectly smooth. 



The female of this species is easily recognized by the peculiar postbasal ex- 

 pansion. The male, however, has a shape which reminds of young Plet}iobasus 

 cyphyus. But P. cyphyus has a lighter yellow epidermis, and has no rays. More- 

 over the beak-sculpture is quite different. 



The range of variation has been already indicated in the description. Dis- 

 regarding the slight tendency to show traces of tubercles in the middle of the 

 shell, the radial furrow is somewhat variable, and also the angle m the middle 

 of the lower margin. The postbasal expansion of the female is very variable, 

 increasing with the age of the individual, but it always is of light color, not dark- 

 green. 



Localities in Pennsylvania represented in the Carnegie Museum: 



Shenango River, Harbor Bridge and Pulaski, Lawrence Co. 



Allegheny River, Aladdin, Godfrey, Johnetta, and Templeton, Armstrong Co.; Walnut Bend, Venango 



Co.; Tionesta and Hickory, Forest Co.; Warren, Warren Co. 

 French Creek, Utica, Venango Co.; Cochranton and Meadville, Cra'ft'ford Co. 

 Connewango Creek, Russell, Warren Co. 



Other localities represented in the Carnegie Museum: 



West Fork River, Lynch Mines, Harrison Co., West Virginia. 



Tuscarawas River, Ohio (Holland collection). 



Columbus, Franklin Co., Oliio (Hartman collection) (Smith collection). 



White River, Rockford, Jackson Co., Indiana (G. H. Clapp, donor) (Wabash-drainage). 



Distribution and Ecology in Pennsylvania (See fig. 34): I have found this 

 species in the Beaver-drainage in the Shenango River,"'" where it is very rare 



^^^ I have not seen it in the Mahoning River in Pennsj'lvania, although it has been reported from 

 this river in Ohio (Lea, 1838; Dean, 1890). 



