CAMBARUS. 73 
of the ground the excavation exhibits a gradual slope, in direction more or 
less undulating for a distance from five to ten inches, when it becomes verti- 
eal for six or eight inches, and then terminates in a sudden bottle-shaped 
enlargement, in which the animal is found. The bottom of the burrow 
having no subterraneous communication, no other issue except towards the 
surface, it is entirely isolated from its neighbors, and leaves no chance for 
escape to its mhabitant. The same burrow may have several external holes 
connected with it, several inclined channels, which, however, meet at the 
depth where it becomes vertical. We found constantly the cavity full of 
water, but this was in March and April. The bottom, for several inches, was 
filled with soft and pulpy mud. 
“There are other instances of burrows somewhat more complex. Their 
direction may be oblique throughout their whole extent, and composed of 
a series of chambers or ovoid enlargements succeeding each other at short 
intervals. Sometimes, also, and connected with one of the chambers, a nar- 
row and nearly vertical tubuliform channel extends downwards to a much 
greater depth, and appears to us as a retreat either during the cold win- 
ters or else during the dryness of the summer, when water is low. That 
it is not for the mere purpose of escaping pursuit, we infer from the fact 
that we repeatedly caught the animals in the chambers above, where they 
remained quietly, instead of attempting to disappear into the apartments 
below. 
“In the spring, and we are told in the fall also, the burrowing craw- 
fish builds over the holes of its burrow a chimney of the maximum height 
of one foot, but most generally lower. The chimney, circularly pyramidal in 
shape, is constructed of lumps of mud, varying in size, irregularly rolled up,. 
and piled up one upon each other, and intimately cemented together. Its 
exterior has a rough and irregular appearance ; whilst the interior is smooth 
and as uniform as the subterraneous channel, having the same diameter as 
the latter. . 
“The animal works during night. How the work is performed has not 
yet been ascertained by actual observations. . . . . On an examination of 
these chimneys, we detected the imprints of the second and third pair of 
claws, which indicate, evidently, that the parcels of mud, once brought to the 
surface, . . . . are arranged and fixed in their definitive place by means of 
these organs. 
“When the work has thus been carried on towards completion, the last 
= Ks) 
