ORT.MANN : THE CRAWFISHES OF THE STATE OF PENNSYLVANIA 411 ' 



far up stream into the smaller tributaries of our rivers, sometimes almost to their 

 sources. The only condition which stops them in an up-stream migration seems to 

 be the character of the watercourse, which must not be too rapid and rough. This 

 is a very important fact, and largely explains the absence of these species in the 

 mountainous regions of the state. On the other hand, these species are by no means 

 averse to quiet bodies of water, such as ponds and lakes, and although tlie parts of 

 Pennsylvania where these species are found are singularly free from lakes, craw- 

 fishes are almost regularly found in them, and even in artificial ponds, reservoii's, 

 etc. It has been observed tliat in ponds and lakes these species seem to tiirive 

 exceptionally well. 



Among the three species belonging to this class, there are certain differences. 

 Cambarus limosu!^ of the eastern part of Pennsylvania has its main abode in the 

 quiet streams of the lowlands. It goes up stream for a certain distance, but rarely, 

 and only under exceptional conditions, (see below), is it found in streams which are 

 somewhat rough. Its center, at least for tliis state, is in the lower part of the Dela- 

 ware River, where it is under the influence of the tides. Here it prefers the muddy 

 banks, living among the water weeds, and congregates often in large numbei-s at the 

 mouths of small streams tributary to the river. In fact the latter places are the 

 most favored, since this species loves to hide under stones, and it is chiefly at the 

 moutli of streams that stones are found in this part of the Delaware. Further up 

 stream, beyond the reach of tlie tide in the Delaware, and in its tributaries (Nesh- 

 aminy Creek, Schuylkill River, Brandywine Creek) and in the Susquehanna and 

 Potomac drainages, this species is generally found hiding under stones, as was 

 first reported b}' Abbott (1873, p. 80) with reference to the Delaware River at Tren- 

 ton, N. J. ]3ut such is not the exclusive habitat of C. limosiis. It is very often 

 found in quiet ponds, in ditches or canals, where there are no stones to afford cou- 

 cealnu'ut. In these places it frequents patches of weeds (J^tllisneria, etc.), often in 

 considerable numbers. From such places (ditches of the Delaware meadows at 

 'I'lviitim) it was reported by Faxon (1885a, p. 88). C. limosits is generally found in 

 very shallow water, but sometimes at a considerable depth. 1 captured a few speci- 

 mens in a quiet cove of the Delaware River at Penns Manor, Bucks County, at the 

 woodwork of a pier, at a depth of from six to eight feet (Sept. 15, 1!K)5), and fre- 

 (luently got numbei-s of it in creeks and canals (Schuylkill Canal, Manayunk ; 

 Delaware and Raritan Canal, Princeton), in the water weeds, at a depth of from two 

 to four feet. Altliough this species loves to hide under stones, and although it 

 scoops out the dirt under stones, it is by no means a Imi rowing species. 'I'lic hol- 

 lows made under stones are very insignificant, and I have never olwerved that it 



