ORTMANN: THE CRAWFISHES OF THE STATE OF PENNSYLVANIA 445 
As has been repeatedly mentioned, C. obscwrus has been discovered in Wills 
Creek, a stream which belongs to the Potomac drainage, at Hyndman, Bedford 
County, Pennsylvania, and Ellerslie, Maryland. ‘This locality is entirely isolated 
and 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 Alleghany Front. In this region, chiefly in the drainage of the upper Youghi- 
ogheny and Castleman Rivers, C. obscwrus 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, Garrett 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 C limosus turns up. Thus 
the presence of C. obscwrus in Wills Creek 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 Pennsy|- 
vania state-line. At Hyndman it is quite abundant, but only below a point about 
half-a-mile south of the railroad station, thus occupying only about 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. I 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 purposes to 
other parts. If C. obscwrus has not been transported in this way to Wills Creek, 
intentionally or accidentally, I have no other explanation to offer. 
The above theory as to the origin of the distribution of the group of C. propin- 
quus explains the facts, as far as I can see. Our knowledge of the distribution of 
