1913] Grinnell-Swarth: Birds and Mammals of San Jacinto 367 



The relatively well developed powers of locomotion of this 

 rodent, even though a species primarily of the lowest zone at 

 the arid base, might be held to account for its invasion Pacific- 

 wards with its pallid coloration scarcely altered at the farthest 

 station on the more humid side of the mountains. It would 

 appear that the index of dispersal of the desert race deserticola 

 is in this region greater than that of the Pacific coast race 

 bennetti. As a result characters of desert origin are carried 

 well over upon faunal ground more properly belonging to the 

 darker coast race. 



Sylvilagus auduboni arizonae (Allen) 

 Arizona Cottontail 



Judging from the results of our collecting, cottontails would 

 seem to be rather uncommon along the desert base of the San 

 Jacinto Mountains. But one specimen was taken, at Banning, 

 2200 feet (no. 1470) ; the species was noted at Cabezon, but none 

 were collected there. There is also a skin from Palm Springs, 

 450 feet (no. 7036) taken December 31, 1903. 



Nelson (1909, p. 220) has referred a specimen from Banning 

 to S. a. sanctidiegi, but while our single example is evidently 

 intermediate between that form and arizonae, its extremely pale 

 coloration seems to justify its inclusion under the latter. The 

 skull is small, and not noticeably different from those of San 

 Diego specimens. 



Evidently the eastern slope of San Gorgonio Pass is with 

 these rabbits, as with several other species of mammals, a region 

 of transition between pallid desert and darker coast forms. 



The Palm Springs example, in winter pelage, is darker col- 

 ored than summer skins of arizonae and with little buffy colora- 

 tion anywhere, but it is distinctly grayish as compared with the 

 richer-colored sanctidiegi. The large audital bullae also place 

 it with the desert race. 



Sylvilagus auduboni sanctidiegi (Miller) 

 San Diego Cottontail 

 Two rabbits taken at Vallevista, 1800 feet, on August 30 

 and September 4, respectively (nos. 2286. 2287), are evidently 



