Bulletin American Museum of Natural History. [Vol. XIX, 



feet more strongly yellowish; ears thinly haired, externally black, 

 internally paler, the tips of the hairs rusty brown ; tail above grizzled 

 black and white, becoming darker towards the tip, the hairs individu- 

 ally alternately ringed with black and soiled whitish, there being three 

 bands of each, and tipped broadly with clearer white; lower surface of 

 the tail pale yellowish white, striped on each side with three longi- 

 tudinal bands of black which increase in width from the inner to the 

 outer, the outer being about twice the width of the inner. 



Total length (type), 520; head and body, 279; tail vertebrae, 241; 

 hind foot, to end of toes, 57, to end of claws, 64; ear, 25. Skull: Total 

 length, 66; zygomatic breadth, 40; length of nasals, 23; upper tooth- 

 row, 13. 



The amount of black on the head varies greatly in different speci- 

 mens, averaging about as above described, but varying from almost 

 none whatever to specimens in which the hairs are black basally with 

 the tips grayish, and through these to clear brownish black; the black 

 area often extends far down over the nape, and occasionally, as abroad 

 median band, to the shoulders, and in one specimen to the middle of 

 the back. 



Doubtless in fresh fall pelage the markings would be about as 

 above described, but with all the tints deeper and hence with greater 

 contrast between the light and dark rings of the individual hairs. 



As already indicated, in many specimens the pelage becomes not 

 only exceedingly worn before the post-breeding moult, but greatly 

 faded and discolored, even the underfur, where exposed, changing 

 from black or blackish to yellow-brown. With this moult the ventral 

 surface changes from pale ochraceous to whitish, more or less mixed 

 with dusky, the basal portion of the hairs being dusky with long whit- 

 ish tips, through which the dusky bases are more or less visible. 



Many of the specimens are in greatly worn and discolored pelage, 

 the ends of the hairs over the posterior half of the body having been in 

 some instances wholly worn away, leaving only the fulvous brown 

 bases, the terminal portion bearing the alternating dark and light 

 rings having disappeared. In most of these the moult is in progress, 

 in some the coat having been renewed on the front half of the body. 



Citellus g. rupestris is represented by 28 specimens, all adult but 3, 

 which are about two thirds grown, collected as follows: Rio Sestin, 

 18, April 1219; Rancho Bailon, 10, May 5-11. Throwing out the 

 young examples, and two with defective tails, the remaining 23 meas- 

 ure as follows: 



Nine males: Total length, 503 (451540); head and body, 277 (241 

 298); tail vertebrae, 233 (210-248); hind foot (without claws), 56.7 

 (55.5-57); ear, from notch, 26.3 (25-28). Fourteen females: Total 

 length, 49^9 (463-521); head and body, 272 (254-293); tail vertebras, 

 227 (203-241); hind foot, 56 (54-60); ear, 26.3 (25-29). 



