410 University of California Publications in Zoology [Vol.12 



The Trinity region shows but very slight endemic individuality. 

 It possesses but five distinguishable races or species of its own, four 

 of which are Boreal and one Sonoran. Only one of these is well 

 marked. 



The failure of the Trinity Mountains to have developed a mark- 

 edly distinct fauna from that of the Sierra Nevada, may be ascribed 

 to three conditions: (1) Absence of extreme, that is, practically 

 insurmountable, barriers, such as a continuous body of water, or a 

 strip of the Sonoran zone, or a belt of excessive aridity; (2) close 

 similarity in those features of climate included in the terra humidity, 

 for zonal identity implies similar temperature conditions at least as 

 to mean; (3) small area as compared with that of adjacent mountain 

 masses which, because of the greater mass of their fauna, have 

 exerted a dominating influence in the interacting processes of 



Transmitted June 29, 191J t . 



LITERATURE CITED 



Anderson, M. P., and Grinnell, J. 



1903. Birds of the Siskiyou Mountains, California: a problem in dis- 

 tribution. Proc. Acad. Nat. Sci. Phila., 1903, 4-15. 

 Grinnell, J. 



1913. A distributional list of the mammals of California. Proc. Calif. 

 Acad. Sci., (4)3, 265-390, pis. 15, 16. 

 Grinnell, J., and Swarth, H. S. 



1913. An account of the birds and mammals of the San Jacinto area of 

 southern California, with remarks upon the behavior of geo- 

 graphic races on the margins of their habitats. Univ. Calif. Publ. 

 Zool., 10, 197-406, pis. 6-10. 

 Kellogg, L. 



1916. Report upon mammals and birds found in portions of Trinity, 

 Siskiyou and Shasta counties, California, with description of 

 a new Dipodomys. Ibid., 12, 335-398, pis. 15-18. 



Merriam, C. H. 



1899. Results of a biological survey of Mount Shasta, California. U. S. 

 Dept. Agric, Div. Biol. Surv., N. Amer. Fauna, 16, 179 pp., 5 

 pis., 46 figs, in text. 



