22 NORTH AMEEICAN" FAUNA. [No. 40. 



Color, — Adult in fresh suramer pelage: Upperparts as in C. ludo- 

 vicianus, but less reddish and much more grayish and vinaceous-buff ; 

 entirely black hairs more numerous, giving a much more grizzled 

 general effect. Cinnamon areas less intense, more vinaceous. Tail 

 above like rump for half its length; terminal half chiefly intense black, 

 the black, extending forward on sides of tail, leaving a lighter area 

 midway; hairs of sides of pencil tipped with whitish, bases of all 

 the pencil hairs almost pure white. Adult in fresh winter pelage: 

 General appearance decidedly hoary or vinaceous-buff, the hairs 

 with broad subterminal bands of whitish, which mix in the general 

 effect with the narrow black tips and cinnamon undercolor. Indi- 

 vidual hairs narrowly black at base, then broadly white and nar- 

 rowly cinnamon, with subterminal band of buff and tip of blackish. 

 The general effect is a glossy marbled vinaceous-buff, making the 

 coat of this species by far the handsomest of all the prairie-dogs. 

 Juvenile specimens are much paler than those of the corresponding 

 age in C. ludovicianus, and rapidly change into a pelage like the 

 fresh autumnal coat of adults. 



Molt. — The molt of C. mexicanus is almost continuous and ex- 

 ceedingly complex, and without series of specimens collected in aU 

 the summer months it can not be worked out satisfactorily. With 

 only March, April, July, and August skins before me I am inclined to 

 beheve that there are three complete renewals of the pelage of the 

 body annually. Specimens collected in March have all renewed 

 below, but are chiefly in the worn winter coat above, except in small 

 areas forward, or even over the greater part of the head, shoulders, 

 and withers, where renewal into a pelage much hke the fresh winter 

 coat has commenced. April skins from Saltillo are in a much-worn 

 condition. The real summer pelage is certainly retained only a 

 short time, as specimens collected at La Ventura from July 19 to 

 August 5 exhibit every condition from what appears to be a worn, 

 faded, left-over winter coat; through renewal into a short, stiff sum- 

 mer coat, without underfur; and the progress of the heavy winter 

 pelage with a dense underfur over the posterior half of the back. 

 Several specimens show all three of these pelages in definite areas on 

 the body. Breeding females, as usual, are slow to renew, and the 

 extreme state of wear is common until after the nursing season is 

 over. 



Slcull and teeth. — Skull broad and angular, with wide-spreading 

 zygomatic arches and sharply defined processes; in general effect 

 more like skulls of C. I. ludovicianus from Montana and the Dakotas 

 than like those of C. I. arizonensis; upper maxillary root of zygoma 

 narrow along contact with ascending premaxillary bones and along 

 ascending arm of jugal; face of upper incisors bright yellow. Differs 

 from skulls of both ludovicianus and arizonensis in its much larger, 



