ORTMANN : THK CUAWFISHES OF THE STATK OF PENNSYLVANIA 427 



Similiir conditions sooni to have played a part in tlie distribution of this species 

 in tlie Potomac River. It lias been reported from an old canal (Chesapeake and 

 Ohio) four miles south of Cumberland, and I have found it in the Potomac at 

 Cherry Run, West V^irginia. and at South Cumberland. At both places it was scarce, 

 and I am much inclined to Indicve that in this region (western Maryland and east- 

 ern West \'irginia) it got into the river from the canal. Originally its distribution 

 in Maryland was very likely similar to that in Pennsylvania, belonging only to the 

 Coastal Plain and the, Piedmont Plateau. ^- 



Of the tributaries of the Potomac in southern I'ennsylvania those which empty 

 into the Potomac east of the Alleghai^y Mountain region also possess this species. 

 It lias ix'en found in the di'ainage of the Monocacy River at ( Jetty sburg, Adams 

 County, and that of the Conococheague-Creek in Franklin County, the latter local- 

 ity again belonging to the ( Jreat Alleghany \'alley. Further west, within the Alle- 

 ghany Mountains, it seems to be absent. I did not fnid it in l>ig Cove Creek and 

 Tonoloway Creek, Fulton County, and it is not in the collections made Ijy Mr. 11. 

 A. Pilsbry for the Philadelphia Academy in Sideling and Town (Jreeks, Wa.shington 

 and Alleghany Counties, Maryland. This supports the view that the presence of 

 this species in the Potomac as far up as Cumberland is due to the existence of the 

 canal. Above Cumberland, where the canal ends, C. limosus is positively absent in 

 the Potomac drainage in Penn.sylvania as well as in Maryland and in West ^'irginia. 



Thus it seems that C Hmosus belongs oi-iginally only to the largei- rivei-s of the 

 southeastern section of our state, and that its real center for Pennsylvania is the 

 Delaware. It has .spread, however. u|)stream, and has approached the Alleghany 

 Mountain region, even entering the latter in the Su.squehanna River. This upstn-am 

 dispersal is apparently not everywhere due to natural migration. l>ut has lieeii 

 favored in recent times by canals. The present northwestern boundary, disregard- 

 ing the Susquehanna River, is marked by a line (.see PI. XLllI) running from New 

 Hope, Bucks County, to Maiden ('reek and Reading, Perks County, thence to P.ain- 

 bridge, Lancaster County, ( "arlisle, ( 'umberland ('ounty. and to Williamson, Frank- 

 lin < 'ounty. 'i'liis line, generally speaking, runs parallel to the I'lue Mijuntain, and 

 it is very likely that the differences in the physical features of the Piedmont Plateau 

 and the .Mleghany Mountains have something to do with the distributi<in of this 

 species, although the real cause cannot an}' longer be clearly .seen, the original con- 

 ditions being apparently obscured l>y several factors. l''or it shoultl not be forgotten 

 that the streams from the Susquehanna to tin- Pclaw.nc. i-suing through the Plue 



*'Tlie Chesapeake and Ohio Canal forms a continuous watiTway from Wa.'<hinnlon to Cumberland, and was com- 

 pleted in 1850, see Hulbert, I'JOl, p. lUO, and map opposite p. SO. 



