ORTMANN: UNIONIDZ OF WESTERN PENNSYLVANIA. 200 
Both forms, ob/gua (Lamarck) and pyramidata (Lea), are repre- 
sented, and some individuals approach Alena (Lea). ‘They all pass 
gradually into each other. In fact the intergrading forms are more 
frequent than typical specimens, so that it is absolutely impossible to 
draw the line between these supposed species. A more detailed ac- 
count of the various forms constituting this very variable species will 
be given elsewhere. 
44. Quadrula coccinea (Conrad). 
The type locality for this species is the ‘‘ Mahoning River near 
Pittsburgh’’ (Conrad). It is present in ‘the Mahoning River at 
Mahoningtown, Lawrence County. It does not occur in Harn’s list, 
although present in the upper Loyalhanna in Westmoreland County, 
and it is not recorded by Stupakoff and Clapp. Rhoads has it from 
the Beaver River at Wampum, Lawrence County. Specimens froro 
this locality are in the Carnegie Museum, collected by Clapp and 
Smith. 
It is generally distributed in the Beaver drainage in Lawrence and 
Mercer Counties. It is found in Buffalo Creek, Butler County; in 
Little Mahoning Creek, Indiana County ; in the French Creek drain- 
age in Venango, Crawford, and Erie Counties ; in Brokenstraw Creek 
in Warren County ; and in the upper Allegheny in McKean County. 
In the Allegheny River from Armstrong to Warren Counties, there is 
a form, which inclines both toward typical Q. od/gua, and the form 
pyramidata. In the southwestern portion of the state (Monongahela 
drainage) this species seems to be absent. 
This species does not belong tothe genus Quadru/a. At the breed- 
ing season, the outer gills only are used as marsupia, and thus it should 
be placed, according to Simpson’s arrangement of the genera, with 
the genus P/leurobema. I possess a number of gravid females from 
Neshannock Creek in Lawrence County, and from the upper Alle- 
gheny in McKean Country. 
45. Quadrula subrotunda (Lea). 
Cited by Harn from western Pennsylvania. The JU. fpilaris of 
Clapp (Allegheny County) and of Rhoads (Coraopolis) are probably 
this form. The majority of Rhoads’ od/guus (Coraopolis and Beaver) 
belong here. 
It is abundant in the larger rivers: Ohio, Monongahela, and Alle- 
gheny. Inthe Monongahela it extends up to the Cheat River in 
Fayette County, in the Allegheny up to the northern part of Arm- 
strong County. 
