ORTMANN: THE CKAWFISHES OF THE STATE OF PENNSYLVANIA 445 



As lias been repeatedly mentione<l, C. obscunis has been discovered in Wills 

 Creek, a stream which belongs to the Potomac drainage, at Hyndman, Bedford 

 County, Pennsylvania, and EUerslie, Maryland. I "his localit}' is entirely isolated 

 iiiid about 40 to 50 miles distant from the nearest parts of the main range in West- 

 moreland and Fayette Counties, separated from the latter by that part of the Alle- 

 ghany Plateau which is included between Chestnut Ridge, Laurel Hill Ridge, and 

 the Alleghan}' Front. In this region, chiefly in the drainage of the upper Youghi- 

 ogheny and Castleman Rivers, C. obscurus is missing, of which fact I am quite posi- 

 tive, having searched for it in vain at the following localities : the Youghiogheny 

 River at Ohiopyle, Fayette County, same river and Laurel Hill Run, Confluence, 

 Somerset County; Youghiogheny River, Selbysport, (iarrett County, ^Maryland ; 

 Castleman River, Rockwood, Somerset County ; Flaugherty Creek, between Meyers- 

 dale and Keystone, Somerset County. 



Under such conditions stream-piracy is out of the question. For some time I 

 suspected that C. obscurus might be present in other parts of the upper Potomac 

 drainage, but this is not the case. I have investigated the Potomac River at Cum- 

 berland, Maryland, and above Cumberland (Rawlings, Alleghany County, Mary- 

 land), and further up, where it forms the boundary between Garrett County, Mary- 

 land, and Mineral and Grant Counties, West Virginia ; but I have not seen a trace 

 of this or any other river-species. Below Cumberland G. limosns turns up. Thus 

 the presence of C. obscurus in Wills ('reek is very local, and restricted to only a 

 small part of the creek. I found it at Ellerslie, Maryland, but not below this point, 

 although I investigated the whole creek from Mt. Savage Junction to the Pennsyl- 

 vania state-line. At Hyndman it is (juite abundant, but only below a point about 

 half-a-mile south of the railroad station, thus occupying only aliout eight or nine 

 miles of the creek. 



These facts are rather strange, and, I believe, can only be explained by the 

 assumption of artificial introduction by human agency. 1 do not think that it was 

 necessarily intentional, but it may be due to accidental stocking of the creek with 

 this species, which is not altogether improbable, if we consider that in this region a 

 good deal of fishing is done, and that fishermen from places between Pittsburgh and 

 Connellsville go over this whole region, and frequently use crawfishes as bait, cap- 

 turing them in one part of the country, and carrying them for their purpo.^^cs to 

 other parts. If ('. obscurus has not been tran.sported in thi.s way to Wills ( 'reek, 

 intentionally or accidentally, 1 have no other explanation to ofler. 



The above theory as to the origin of the distribution of the group of C jtroiiin- 

 quus explains the facts, as far as I can see. Our knowledge of the ilistribution of 



