ORTMANN: 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 the 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, reservoirs, 
ete. It has been observed that in ponds and lakes these species seem to thrive 
exceptionally well. 
Among the three species belonging to this class, there are certain differences. 
Cambarus limosus 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 this 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 numbers 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 
mouth of streams that stones are found in this part of the Delaware. Further up 
stream, beyond the reach of the 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 by Abbott (1873, p. 80) with reference to the Delaware River at Tren- 
ton, N. J. But such is not the exclusive habitat of C. /umosus. It is very often 
found in quiet ponds, in ditches or canals, where there are no stones to afford con- 
cealment. In these places it frequents patches of weeds (Vallisneria, ete.), often in 
considerable numbers. From such places (ditches of the Delaware meadows at 
Trenton) it was reported by Faxon (1885a, p. 88). C. limosus is generally found in 
very shallow water, but sometimes at a considerable depth. I 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, 1905), and fre- 
quently got numbers 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. Although this species loves to hide under stones, and although it 
scoops out the dirt under stones, it is by no means a burrowing species. The hol- 
lows made under stones are very insignificant, and I have never observed that it 
