MAMMALS OF THE MEXICAN BOUNDARY, ^98 



sioiially touch each other or are separated b}^ an interval a few miles 

 broad or a few hundred feet in altitude. The narrow intermediate 

 zone is occasionally occupied by the Say chipmunk {CaJlospermo- 

 philus latei'alis)^ which species, however, has almost the same area 

 of distribution as the Arizona chi})nuni]v. At Stonemans Lake, on 

 the northwestern slope of the Moi^'ollon range, having an altitude 

 of O.^IT) feet, this species is very nmnerous, findino- in the rocky walls 

 of the lake basin a satisfactory abode; but l>etween that point and 

 the summit of the mountain is a pine forest free from rocks quite 

 unsuited to the present species. In traversing this forest, which rises 

 gradually to near the sunnnit of the range. Say's was the only chip- 

 munk found until a certain altitude (about G.rtOO feet) was reached, 

 when the first Arizona chipnnniks appeared, whereupon both species 

 {C(tUo!^permop]itli(S lateralis and Eutaniias rinej'cirollis) became 

 gradually more abundant until the top was reached. The large area 

 of Tonto Basin is bounded on the north by a nearl}^ vertical precipice, 

 or " rim-rock," hundreds of feet high, Avhose summit marks the back- 

 bone of the Mogollon Mountains. This is the tyj^ical home of Euta- 

 mias cfnereieoHi^. while the basin itself is an equally populous strong- 

 iiold of the Cxila chipmunk. Nowhere have I seen so palpable a line 

 of division l)etween two contiguous species, and I imagine that few 

 Pjaturidists, seated on this fence, would hesitate about the separation 

 of these two distinct mammals, whose habitats touch each other, 

 while each retains all of its distinctive characters. 



AVest of the Verde Valley, a few Gila chipmunks were noted March 

 26, 1885, in rocky places between Antelope and Bumble Bee post- 

 offices, in Yavapai County, Arizona ; and some were seen farther 

 south, in Black Canyon, the next day. I saw some of them near 

 Mountain Spring, east of Tucson, Arizona, April 8, 1885. The banks 

 of Ash Creek, Agua Fria Valley, which were wooded with scrub oak 

 and lined by rocky bluffs, were inhabited by numbers of these chij^- 

 munks May 19, 1885. 



The Gila chipmunk crosses the Mexican Boundary Line in a narrow 

 belt, including the San Luis and Guadalupe mountains (Monuments 

 Nos. G4 to 75). Xone were found east or west of this area. The ab- 

 sence of any species of chipmunk from the Huachuca Mountains is 

 remarkable. 



In the San Luis Mountains the young are apparently born during 

 July. Adults caught June 24, 26, and July 20, contained, respec- 

 tively, 3, 2, 8, and 7 fetuses. 



On the Mexican Border the vertical range of the Gila chipmunk 

 was noted as from 1,200 meters (in Guadalupe Canyon) to 2,498 

 meters (summit of San Luis Mountains, where it was fairly common). 

 In Cajon Bonito Canyon it is abundant: some had descended as low 

 as 1,200 meters, and were active late in September, 1893. 



