4 BULLETIN 1091, IT. S. DEPARTMENT OF AGRICULTURE, {eS^No 03 ] 
lack the conspicuous white hip stripe possessed by all the latter ; and 
(c) the kangaroo rats (Dipodomys) . 
Dipodomys spectabilis spectabilis Merriam requires comparison 
with three other forms of kangaroo rats in the same general re- 
gion, namely, D. deserti Stephens, of approximately the same size, 
and D. merriami Mearns and D. ordii Woodhouse, the last two of 
decidedly smaller size. The range of deserti lies principally to the 
Fig. 1. — Range, east of the Colorado River, of Dipodomys speotabilis spectabilis com- 
pared with that of Dipodomys merriami. Cross hatching indicates area of overlapping 
of the two forms. The range of Dipodomys deserti. not shown on the map, is west of 
that of spectabilis, and so far as known the two do not overlap. 
west of that of spectabilis. and the two do not, so far as known, over- 
lap. On the other hand, merriami and ordii, and subspecies, occur over 
a large part of the range of spectabilis, living in very close proximity 
to its burrows ; merriami is even suspected of pillaging the stores of 
spectabilis. The range of merriami, however, is much more exten- 
sive than that of spectabilis (Fig. 1), which argues against a definite 
ecological dependence or relationship. Separation of the four forms 
mentioned may be easily accomplished by the following key : 
