Ortmann : Unionid.-e of Western Pennsylvania. 195 



agree with typical eastern specimens, and generally, in the mountain 

 streams (Cheat, Youghiogheny, Loyalhanna, Quemahoning) this 

 species remains as small as the eastern form. On the other hand I 

 have eastern specimens, which are larger than any western specimens 

 (see below). Several series containing specimens of all sizes, from 

 various localities, both in the eastern and western drainage, show that 

 there actually is no difference whatever between the two supposed 

 species, and I challenge anyone to identify them, when the locality is 

 not known. 



25. Anodonta imbecillis Say. 



Not reported previously from the state. I found it only in Erie 

 County, in Conneauttee Lake, and in the outlet of Lake Leboeuf. 



26. Anodonta grandis Say. 



This species occurs in none of the older lists, but there is a specimen 

 in the Carnegie Museum collected in 1897 by Clapp in an artificial 

 pond at Edgeworth, Allegheny County. 



The typical form (rather heavy-shelled, elongate, dark-colored) is 

 not rare over the western part of the state, and prefers the smaller 

 streams, where it is sometimes found in abundance in quiet pools. It 

 goes eastward as far as Westmoreland, Indiana, and Warren Counties. 

 In the larger rivers it is generally absent, although single specimens 

 (chiefly young ones) turn up here and there. In stagnant ponds a 

 large, thin shelled, higher, and beautifully colored form (var. gigantea 

 Lea) is encountered. This form is quite abundant in a pond (aban- 

 doned ox-bow of the Allegheny) at Harmarville, Allegheny County. 

 A similar form, but with a peculiar green color (similar to var. bene- 

 dictensis Lea 1) occurs in Conneaut Lake, together with a very thin- 

 shelled, light green, elongate form. A similar form to the latter, but 

 of a darker color, is found in the black muck of Conneauttee Lake in 

 Erie County. The var. salmonia Lea, which has been regarded as 

 a pathological form, is rather frequent in the northwestern section of 

 the state, and, as is quite remarkable, at certain places is found to the 

 exclusion of the typical form. 



27. Anodontoides ferussacianus (Lea). 



Not reported previously. It is found in the northwestern corner of 

 the state, in Mercer and Crawford Counties, in the drainage of She- 

 nango River and French Creek. It is most abundant in the Upper 

 Shenango at Linesville, Crawford County, and in Conneaut Lake and 

 Conneaut Outlet. At the latter localities, the specimens very closely 

 resemble in shape the var. subcylindraceus (Lea). 



