1913] Grinnell-Swarth: Birds an<i Mammals of San Jacinto 333 



eter of the San Jacinto region. It is probable that in these 

 animals the higher mountain ridge serves as a barrier. Although 

 obviously of no great length and even not continuous, this 

 barrier is doubtless to some degree effective in isolation. 



It is the animals of the lowest zone which exhibit the most 

 divergent characters at the two faunally most divergent bases of 

 the mountain. 



Peromyscus truei martirensis (Allen) 

 San Pedro Martir Rig-eared Mouse 



As indicated by our trapping, this mouse is. with the exception 

 of P. c. stephensi, the least common of the genus in the area 

 explored. But fifteen examples were secured, as follows: Santa 

 Rosa Peak, 7500 feet, six (nos. 2029-2034) ; Strawberry Valley. 

 6000 feet, two (nos. 2127. 2138) ; Kenworthy. 4500 feet, five I nos. 

 1797. 1808-1810, 1913) ; Dos Palmos Spring. 3000 to 3500 feet, 

 two (nos. 1914, 1915). 



They were trapped only on dry chaparral-covered hillsides. 

 As noted from the localities of capture there is considerable zonal 

 range. Dos Palmos Spring being well down into the area of 

 blending of Upper with Lower Sonoran, while the stations on 

 Santa Rosa Peak and in Strawberry Valley were in areas of 

 mingling of Upper Sonoran and Transition elements. It would 

 appear that Upper Sonoran chaparral of the Pacific slope is the 

 locally preferred habitat of this mouse. 



We follow Osgood (1909, p. 171) in the name assigned to 

 this mouse. The series is pale-colored as compared with repre- 

 sentatives of truei from Mount Pinos, Ventura County. The 

 latter are evidently somewhat intermediate towards P. f. gilberti. 

 Our examples, however, have not nearly so long tails as the 

 measurements given for topotypes of martirensis. Thirteen 

 adults give a tail length of 102.5 (83-111) as contrasted with 

 "116.5 (112-122)." It is evident that the San Jacinto animals 

 average somewhere between typical truei and martirensis in sum 

 total of characters, though not deserving of separate recognition 

 i n nomenclature. 



