10 BULLETIN 1091, U. S. DEPARTMENT OF AGRICULTURE. {e^^No^I, 
ing heights above the general surface of the surrounding soil, the 
height depending rather more upon the character of the soil and the 
location of the mound as to exposure or protection than upon the 
area occupied by the burrow system which lies within and is the 
reason for the mound. 
A den in sandy soil in the open may be of maximum size in area 
occupied and yet scarcely present the appearance of a mound in any 
sense, due probably both to the fact that the sandy soil will not heap 
up to such a height over a honeycomb of tunnels as will a firmer or 
rocky soil, and also to its greater exposure to the leveling action of 
rains and the trampling of animals. These mounds are in themselves 
large enough to attract some attention, but their conspicuousness is 
enhanced by the fact that they are more or less completely denuded 
of vegetation and are the centers of cleared areas often as much as 
30 feet in diameter (PI. V, Fig. 1) ; and further that from 3 to 12 
large dark openings loom up in every mound. The larger openings 
are of such size as to suggest the presence of a much larger animal 
than actually inhabits the mound. Add to the above the fact that 
the traveler by day never sees the mound builder, and we have the 
chief reasons why curiosity is so often aroused by these habitations. 
On the Range Reserve the mounds are usually rendered conspicuous 
by the absence of small vegetation, but Nelson writes that in the 
vicinity of Gallego, Chihuahua, they can be readily distinguished at 
a distance because of a growth of weeds and small bushes over their 
summits, which overtop the grass. In the vicinity of Albuquerque. 
N. Mex., Bailey reports (and this was recently confirmed by Vorhies) 
that the mounds about the holes of spectahilis are often hardly 
noticeable. Hollister writes that in the yellow-pine forests of the 
Gallina Mountains the burrows are usually under the trunk of some 
fallen pine, both sides of it in some cases being taken up with holes, 
there being some eight or ten entrances along each side, the burrows 
extending into the ground beneath the log. In the vicinity of 
Blanco, N. Mex., Birdseye says that occasionally spectahilis makes 
typical dens but more often lives in old prairie-dog holes {Cynomys) . 
or in holes which look more like those of D. ordii. 
Runways and Tracks. 
Still other features add to the interest in the dwelling places of 
spectahilis. Radiating in various directions from some of the open- 
ings of the mounds Avell-used runways are to be seen, some of them 
fading out in the surrounding vegetation, but others extending 30, 
40, or even 50 or more yards to neighboring burrows or mounds (PI. 
V, Fig. 2; PI. VI, Fig. 1). These runways and the entrances to the 
mounds are well worn, showing that the inhabitants are at home and 
