LIFE AREAS 287 



same Realm bounded alx)ve or on the north l)y the summer 

 isotherm of 63 degrees, and below or south by the summer 

 isotherm of 70 degrees; an Upper Austral Life Zone lying be- 

 tween the summer isotherms of 70 degrees and yy degrees; a 

 Lower Austral Life Zone, consisting of the remainder of the 

 North Temperate Life Realm and a Sub-Tropical Life Zone, con- 

 sisting of the northern part of the Tropical Life Realm. This 

 covers but a small area in southeastern California. That part of 

 the Arctic Life Zone in California is still smaller, consisting of a 

 few small isolated areas on the highest mountain summits. 



The distribution of life being affected also by the greater or 

 less average amount of moisture present in a given area, and as 

 this average amount of moisture varies in portions of each life 

 zone, it follows that the distribution of life is not equal through- 

 out a life zone. To give expression to the effects of the varying 

 amounts of moisture in life realms and life zones, they are di- 

 vided in sections of variable size called regions, sub-regions and 

 provinces. That part of the North Temperate Life Realm on 

 this continent is known as the North American Region. That 

 part of this region in western North America having a small an- 

 nual rainfall is known as the Arid Sub-Region, and the part near 

 the sea having a large rainfall is the Pacific Coast Sub-Region. 

 The Arid Sub-Region has been divided into twO' provinces : the 

 Sonoran Province, consisting of that part in the Lower Austral 

 and Sub-Tropical Zones; and the Campestrian, consisting of that 

 part in the Upper Austral and Transition Zones. 



I propose further subdividing the life areas of California 

 into Faunas, to consist of areas of nearly equal temperature, 

 moisture and soil, and therefore a nearly homogeneous local 

 assemblage of life forms. These will not be equal in either size 

 or value, and are intended only to facilitate the study of distribu- 

 tion of species in California. The boundaries of Life Zones and 

 Faunas as indicated on the accompanying map are only pro- 

 visional ; further study will necessitate numerous changes. 



The Californian Arctic Fauna is that part of the Arctic Life 



