I9O THE AMERICAN NATURALLIST. [Vor. XXXV. 
whole, I think that, for this species at least, the theory of 
Tarr! and Shufeldt,? that the chimney is simply the deposi- 
tion of the material brought up from the burrow, is correct. 
The mud is brought up in very soft condition, and I think that 
even if the burrow were made in the sloping side of a ditch 
there would be little danger of the pellets rolling down, as 
suggested by Abbott ;? in fact I have examined several burrows 
on the sides of ditches, presumably in the same kind of posi- 
tion as those examined by Mr. Abbott, and I have not been 
able to convince myself that anything except the easiest 
method of disposing of material from the burrows could have 
prompted the animal to build chimney-like structures. The 
quantity of material brought up is very considerable, amounting 
in some cases to nearly two hundred cubic inches. 
As suggested above, the accidental sealing of the burrows 
would seem to be impossible. I believe that I found the 
“ dumps " in enough different stages of construction to war- 
rant the conclusion that the opening through the tower is left 
open until the last, when it is closed by stopping with mud 
brought from below. The opening is thus filled solidly from 
the top, or near the top, to almost the level of the ground, 
where the shaft has a concave hemispherical end, which is 
not so smooth as Shufeldt's* description of the burrow of 
C. diogenes would seem to indicate. And I cannot agree with 
him that the animal might have used the lateral tail fins in 
finishing this off, since I have never seen impressions in the 
mud which would indicate such a method, while there are 
many marks which would indicate that the animal had run the 
ends of the chelz into the soft mud. In at least one case 
which I examined, the burrows had been filled to somewhat 
below the surface of the ground with clay so tightly packed 
that it would seem impossible that it might have fallen in by 
accident. The shaft usually goes straight down, but in some 
! Tarr, Ralph. Habits of Burrowing Crayfish in the United States, ature, 
vol. xxx (1884), p. 127. 
? Shufeldt, R. W. 
Chapters on the Natural History of the United States. 
New York, 1897. 
3 Abbott, C.C. Are the Chimneys of Burrowing Crayfish Designed? Amer. 
Nat., vol. xviii (1884), p. 11 Lvl t Shufeldt, R. W. Loc. cit. 
