30 BULLETIN 1091, U. S. DEPARTMENT OE AGRICULTURE. {Si^No!^ 
While there is greater complexity in the larger, and probably 
older, mounds than in the smaller, all are extremely complicated and 
can only be described as labyrinthine in character. The tunnels wind 
about through the mound, rising and falling in vertical depth, inter- 
communicating frequently, but with occasional cul-de-sacs, and in 
places expanding into chambers, of which there may be three or four 
large ones. The stored materials are found in some, but not neces- 
sarily all. of these chambers, and may also occupy considerable 
lengths of ordinary tunnel, especially when the quantity present is 
large. Small evaginations of the tunnels frequently contain lesser 
caches, and it is in such pockets that bits of fresh material are placed 
during a growing season, or that grain supplied the previous night 
for bait is usually found. 
The main masses of storage are most often found centrally located 
at depths of from 15 to 57 centimeters, although at times one may 
find a cache near the periphery of the system and as near the surface 
as 2 or 3 centimeters. In the latter case the materials are subject to 
wetting from rains, and consequent spoilage. 
The major portion of the whole tunnel system is within about 
50 centimeters of the surface of the mound, but usually some one 
branch tunnel goes to somewhat greater depth, and this is likely to be 
the one containing the nest ; this is also likely to extend toward or 
beyond the periphery of the main system, and always ends blindly. 
Such a one, from which two young were taken on January 31. 1920, 
was at a depth of about 65 centimeters, and about 1-| meters beyond 
the periphery of the mound itself. 
The individual tunnels average about 8 centimeters in height, and 
about 11 centimeters in width, though the variation, especially in 
width, is considerable. The expansions mentioned as being the chief 
places of storage are from 15 to 25 centimeters in diameter, and 
may or may not involve a considerable increase in height. They are 
frequently located at junction points of two or more branches of the 
tunnel system. 
The nest cavity is a chamber of approximately spherical shape 
and from 17 to 23 centimeters in diameter. Chambers of this 
character were observed and noted as " old storage " in a number of 
cases. They were sometimes cut off from the rest of the habitation, 
and at first were supposed to contain abandoned musty storage. As 
experience in excavating and interpreting results has been gained 
we have concluded that these chambers in fact represent abandoned 
nests. 
Bailey gives the dimensions of nest chambers observed in New 
Mexico as about 6 by 8 inches to 8 by 10 inches. The nest is com- 
posed of finer, softer, and more chaffy material than the regular 
