VII. A PRELIMINARY LIST OF THE UNIONID^ OF 



WESTERN PENNSYLVANIA, WITH NEW LOCALITIES 



FOR SPECIES FROM EASTERN PENNSYLVANIA. 



By Dr. A. E. Ortmann. 



Several years ago, the writer, in pursuance of his studies of the fresh- 

 water fauna of Pennsylvania, began to collect the freshwater shells. 

 The past summer (1908) was especially favorable for collecting 

 Unionidas, on account of the low stage of the rivers, and a good deal 

 of work was done in this group, so that it is believed that the study of 

 the mussels has progressed far enough to make it possible to give a 

 general account of the Unionidse of the western half of the state. 



The region investigated covers not only the drainage of the upper 

 Ohio (Monongahela and Allegheny Rivers), but also that of Lake 

 Erie, and some of the tributaries of the Susquehanna. The latter have 

 not, however, been as thoroughly studied as the streams lying to the 

 west of the divide. A number of additional localities are situated in 

 southeastern Pennsylvania. 



Before we give our list of species, it seems to be well to mention and 

 discuss the previous records of the Unionidse of western Pennsylvania, 

 since in many cases the nomenclature has changed, and since several 

 incorrectly identified species have been listed. 



In the older publications we have only a few records from our region. 

 I was only able to find the four following : 



Unio aesopus Green (Contr. Maclur. Lye, I, 1827) = Pleurobema 

 asopits (Green). 



Described from the "rivers in the neighborhood of Pittsburgh." 

 Still present in the Ohio below, and in the Allegheny above Pittsburgh. 



Unio circulus Lea (Observ., I, 1834) =: Ohovaria circulus (Lea). 



Cited by Lea from the Monongahela River at Pittsburgh. The 

 locality is now barren, no Unionid?e being any longer present in the 

 immediate vicinity of Pittsburgh. Nevertheless a few years ago this 

 species was still present in the Ohio River below Pittsburgh. 



Unio coccineus Conrad (Monogr., 3, 1836, and Lea, Observ., II, 

 1838) = Qiiadnila cocci nea (Conrad). 



178 



