e 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 1-1/2 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.

[Illustration: FIG. 3.--Diagram of the system of surface runways and
subsidiary dens of _Dipodomys spectabilis spectabilis_. The underground
tunnels of the main den were too complicated to illustrate on this
scale, being very similar to those of Figure 2. The underground tunnels
of the subsidiaries are shown in solid black. Some runways fade out in
the grass in a manner that can not be indicated in a line drawing.]

Bailey gives the dimensions of nest chambers observed in New Mexico as
about