^p^Sta. } LIFE HISTORY OF THE KANGAROO RAT. 7 



dusty sand, they soon recover their normal sleek appearance. Ap- 

 parently the former condition is due to an excess of oil, the latter 

 to the absorption of the excess in a dust bath. The oil is doubtless 

 an important adjunct to the preservation of the skin and hair amid 

 the dusty surroundings in which the animal lives. 



MEASUREMENTS AND WEIGHTS. 



External measurements include : Total lengthy from tip of nose 

 to tip of tail without hairs, measured before skinning; tail vertehrce^ 

 length of tail from point in angle when tail is bent at right angles 

 to body to tip of tail without hairs ; and hind foot^ from heel to tip 

 of longest claw. 



The following are measurements of a series from the U. S. Range 

 Reserve : 



Averages for 17 adult females : Total length, 326.4 millimeters 

 Total length, 326.2 millimeters (349-310) ; tail vertebrae, 188.4 (208- 

 180) ; hind foot, 49.5 (51-47) ; the average weight of 29 adult speci- 

 mens of both sexes was 114.5 grams (131.9-98.0). 



Averages for 17 adult females: Total length, 326.4 millimeters 

 (349r310) ; tail vertebrae, 188.8 (208-179) ; weight (16 individuals), 

 113.7 (131.9-98.0) ; excluding pregnant females, 13 individuals 

 averaged 112.9 grams (131.9^98.0). 



Averages for 13 adult males: Total length, 326 millimeters (345- 

 iSll) ; tail vertebra?, 187.8 (202-168) ; weight, 116.8 grams (129-100). 



There appears to be no significant difference in the measurements 

 and weights of males and females, with the possible exception of the 

 comparison of adult males and adult nonpregnant females, 



OCCURRENCE. 



GENERAL DISTRIBUTION. 



Di'podomys spectaibilis sj)ectahUis is found in southeastern Ari- 

 zona, in northwestern, central, and southern New Mexico, in ex- 

 treme western Texas, in northern Sonora, and in northern and 

 : central Chihuahua (Fig. 1). A subspecies, D. s. cratodon Merriam, 

 has been described from Chicalote, Aguas Calientes, Mexico, the 

 geographic range of which lies in central Mexico in portions of the 

 States of Zacatecas, San Luis Potosi, and Aguas Calientes. 



HABITAT. 



In the Tucson region sjjectahilis is typically a resident of the Lower 



, Sonoran Zone. This is perhaps the principal zone inhabited over 



its entire range, but the animal is often found in the Upper Sonoran 



ilso, and in the Gallina Mountains of New Mexico Hollister found it 



