MAMMALS OF THE MEXICAN linl'NDARY. 



1 1 5 



are compared. The characters of the skull and teeth are shown in 

 the accompanying ftgure (fig. 88) of the type-specimen. 



Local distribution. — The California brush mouse is an abundanl 

 inhabitant of brushy localities of the Pacific Coasl Tract. It is com- 

 monlyfound in the chemizo I hickets. Specimens taken at Nachoguero 

 Valley, Lower California, and on the Laguna Mountains, California, 

 Juno 8 and 15, \S\)A, contained 2 and 3 fetuses, respectively. 



This elegant species, long since accurately described by Professor 

 Baird, is typical of the group of brush mice, which are somewhat inter- 

 mediate between the wood mice and desert mice. This group inhabits 

 the Sonoran — usually only the Upper Sonoran — and Transition /ones 

 along the Mexican Boundary Line, from Texas to the Pacific; some- 

 times it penetrates the Lower Sonoran, or even crosses the Transition 

 Zone, reaching the lower edge of the Boreal. A straggler was taken 

 at the eastern base of the Coast Range Mountains, in California: one 

 was taken at Mosquito Springs, 

 f nihuahua (Monument No. 46); 

 one was found quite low on the 

 Franklin Range, in western Texas; 

 and three were obtained at Fort 

 Clark, Kinney County, Texas. 

 These all came from the Lower 

 Sonoran Zone, where, however, 

 they are mere stragglers from the 

 higher zones, the brush mice being 

 inhabitants of brushy or forested 

 mountains in the altitudinal zone 

 between the habitats of the desert 

 and plains mice and the habitat 

 of the Arizona wood mouse (Peromyscus sonoriensis rujinus). On the 

 Hachita, San Luis, San Jose, and Huachuca mountains the subspecies 

 pinalis ranged from base to summit, and P. sonoriensis rujinus was not 

 found; but in the Chiricahua, Mogollon, White, Graham, San Francisco, 

 and other high ranges of mountains in Arizona and New Mexico P. s. 

 rujinus occupies the Douglas spruce and aspen zone about the sum- 

 mits; and P. boylii pinalis is only found lower down, in the forest belts 

 of pine, piilon, alligator juniper, cedar, and brushwood. As a rule, at 

 least in the interior tract, the forms of P. boylii do not descend tut he 

 lowest valleys, even when these are wooded; and on the open 

 country — the habitat of the desert mice (Peromyscus eremicus group) 

 and plains mice {Peromyscus sonoriensis group) —it occurs only as an 

 accidental straggler. 



Professor Baird's type of Peromyscus boylii was obtained on the 

 Middle Fork of the American River, in Eldorado County, California, 



Fig. 88.— Peromyscus boylii. Skull and teeth 

 of type, a, skull, dorsal view; b, crowns 

 of lower molars; c, crown of upper molars. 



