ORTMANN: UNIONID© OF WESTERN PENNSYLVANIA. 192 
13. Proptera gracilis (Barnes). 
Not in Harn’s list. Recorded by Clapp from Allegheny County, 
and by Rhoads from the Ohio River. 
Abundant in the Ohio below Pittsburgh ; rare in the Allegheny in 
southern Armstrong County. Formerly in the Monongahela at Char- 
leroi, Washington County (Ehrmann Collection). Nowhere else. 
14. Obovaria retusa (Lamarck). 
Not reported previously from the state. A single live specimen 
(gravid female) was found by the writer in the Ohio at Industry, 
Beaver County. Subsequently a well preserved dead shell of a male 
was found at the same place. 
15. Obovaria circulus (Lea). 
Lea records this species from the Monongahela at Pittsburgh. It is 
reported by Harn from western Pennsylvania, and by Rhoads as 
U. lens from the Ohio and Beaver. 
The writer has seen many dead shells from the Ohio in Allegheny 
County. One living specimen, taken August 1, 1906, was the last 
living Unionid found in the Ohio in Allegheny County. ‘here are 
specimens taken from the Monongahela at Charleroi, Washington 
County, in the Ehrmann Collection. It is found living in the Mahon- 
ing and Shenango Rivers and in Pymatuning Creek, Lawrence and 
Mercer Counties. It occurs also in Crooked Creek in Armstrong and 
Indiana Counties. It is now rather scarce. 
In the Ohio, the form cz7cw/us prevails, while in the smaller creeks 
it generally takes the more compressed shape of O. Zens (Lea) ; but 
all manner of transitional variations between the two forms occur. 
O. circulus and lens are not the male and female, as Sterki believes. 
16. Obovaria (Pseudoon) ellipsis (Lea). 
Recorded by Stupakoff from Allegheny County, but in no other list. 
The writer found two specimens in the Ohio at Industry, Beaver 
County. 
17. Plagiola securis (Lea). 
Reported in Harn’s list from western Pennsylvania ; in Clapp’s list 
from Allegheny County, in Rhoads’ list from the Ohio. 
Rather abundant in the Ohio in Beaver County ; formerly occurred 
in the Monongahela at Charleroi, Washington County (Ehrmann Col- 
lection). Very rare in the Allegheny in southern Armstrong County. 
Nowhere else. 
18. Plagiola (Amygdalonajas) elegans (Lea). 
