402 Annals of the Carnegie Museum. 



propinqiiHS the tip of the internal part is pointed, while in C. obsairus 

 it is blunt. 



Cambarus propinquiis is restricted, in Pennsylvania, to Lake Erie 

 and the Lake Erie drainage. In the lake itself it has been found at 

 Presque Isle (Dr. D. A. Atkinson coll.), and near Miles Grove 

 (picked up alive on the beach by the writer). Of the tributaries of 

 the lake, it is present in Conneaut Creek, associated with C.'obscurus, 

 at Albion, Erie county, but is exclusively found in some smaller creeks 

 running to Conneaut Creek, Temple Creek at Albion, and in a small, 

 nameless tributary below Conneautville Station, Crawford county. 

 With C. obscurus it is found in Elk Creek, between Girard and Miles 

 Grove, and it is found without C. obscurus in Walnut Creek at 

 Sw^anville. 



The largest specimens of C. propinquiis in the Carnegie Museum col- 

 lections are from Albion, Erie county, and measure : male of first 

 form, 61.5 mm. ; female, 69 mm. Hagen gives 2.3 in. = 66 mm. 

 for this species. 



6. Cambarus obscurus Hagen. The River Crawfish. 



The differences from C. propinquus have been set forth above, and 

 are the following: (i) Lack of median keel of rostrum; (2) arma- 

 ture and shape of chela, which, however, is well developed only in 

 large males of the first form ; (3) shape of male copulatory organs; 

 (4) shape of annulus of female; (5) color of finger-tips. (In old, 

 dirty and soiled shells the color markings are largely obscured.) 



Hagen gives 3.5 in. = 89 mm. for this species. The largest speci- 

 mens in our collections are : male of first form from Ohio River, Stowe 

 and Neville townships, Allegheny county, 86 mm.; female from 

 Pucketty Creek, Allegheny county, 93 mm. 



C. obscurus is the river form of western Pennsylvania, and prefers 

 larger streams. Generally, the specimens are found under stones, 

 where they scoop out a little hole for their accommodation. Rarely 

 they dig short tunnels, and they do this chiefly on gravelly banks in 

 the rivers, where there are no larger stones. If stones are lacking, 

 they make short holes in muddy or peaty banks. These holes are 

 very artless, running generally in a horizontal direction for a few 

 inches, rarely more than a foot, just below the level of the water. 

 The workings of this species are often indicated by insignificant mud 

 or sand piles in front of their holes, generally more or less obliterated 

 by the action of the water. 



