6 BULLETIX 1091, U. S. DEPARTMENT OF AGRICULTURE. | Buh! Nal 



longer than the body. Cranium triangiUar. tlie occiput forming the 

 base and the point of the nose the apex of the triangle, much flat- 

 tened, auditory and particularly mastoid bullae conspicuously in- 

 flated. 



COLOR. 



General color above. broAvnish buffy. varying in some specimen^ 

 to lighter buffy tints, grizzled with black: oblique hip stripes white d 

 tail with dark-brown or blackish stripes above and below, running 

 into blackish about halfway between base and tip, and with two 

 lateral side stripes of white to a point about halfway back; tail 

 tipped with pure white for about 40 millimeters (PL I). Under-, 

 parts white, hairs white to bases, with some plumbeous and buffyl 

 hairs about base of tail: fore legs and fore feet white all around: 

 hind legs like back, brown above, hairs with gray bases, becoming 

 blackish (fuscous-black or chsetura-black) about ankles, hairs on 

 under side white to bases: hind feet white above, dark-brown oi 

 blackish (near fuscous) below. 



Color variations in a series of 12 specimens from the type locality 

 and points widely scattered through the range of spect-ahilis consist 

 in minor modifications of the degree of coloration, length of white 

 tip of tail, and length of white lateral tail stripes. In general the 

 color pattern and characters are remarkably uniform. Young speci-v 

 mens, while exhibiting the color pattern and general color of adults ' 

 are conspicuously less brown, and more grayish. 



There appears to be little variation in color with season. In the 

 series at hand, most specimens taken during the fall, winter, and, 

 spring are very slightly browner than those of summer, suggesting! 

 that the fresh pelage following the fall molt is a little brighter than, 

 is the pelage after being worn all winter and into the following 

 sunmier. But at most the difference is slisfht. 



OIL GLAND. 



I 



Upon separating the hairs of the middle region of the back about 

 a third of the distance between the ears and the rump, one uncovers| 

 a prominent gland, elliptical in outline, with long axis longitudinal" 

 and about 9 millimeters in length. The gland presents a roughened 

 and granular appearance, and fewer hairs grow upon it than else-w 

 where on the back. The hairs in the vicinity are frequently matted. 

 as if with a secretion. In worn stage of pelage the gland may bt 

 visible from above without separating the hairs. Bailey has sug- 

 gested that this functions as an oil gland for dressing the fur, and 

 our observations bear out this view. Kangaroo rats kept in cap- 

 tivity without earth or sand soon come to have a bedraggled ap- 

 pearance, as if the pelage were moist. When supplied with fine 



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