386 University of California Publications in Zoology [Vol. 10 



as recurring periods of extreme food shortage, epidemic disease, 

 and cataclysmic disturbances of either climate or topography. 



Table (1) showing relative numbers of boreal mammals represented 

 on the different mountain masses of southern California. Note the 

 correlation of numbers of types with size of the detached area of Boreal 

 (and Transition) zone in each case (see profile, pi. 7). 



Marmota flaviventer 

 Callospermophilus ehrysodeirus, 



subsp. 

 Eutamias alpinus 

 Eutamias speciosus, subsp. 

 Sciurus griseus, subsp. 

 Sciurus d. albolimbatus 

 Sciuropterus alpinus, subsp. 

 Neotoma e. einerea 

 Microtus m. dutcheri 

 Microtus mordax, subsp. 

 Thomomvs alpinus -f- T. alti- 



vallis 

 Zapus t. alleni 

 Erethizon epixanthum 

 Oehotona albatus 

 Lepus c. sierrae 

 Canis lestes 

 Vulpes necator 

 Gulo luteus 

 Mustela arizonensis 

 Neosores p. navigator 



Total number of species 20 



