22 University of California Publications in Zoology [Vol. 27 
Hyla regilla, which is suited by various environments, transcends 
all zonal boundaries. Aneides lugubris, which is closely restricted 
ecologically, is almost strictly confined to the Upper Sonoran Zone 
where its shelter, the live oak, occurs, and its geographic range does 
not exceed the range of that tree. Bufo boreas halophilus occurs in 
the Lower and Upper Sonoran zones in the Sacramento and San 
Joaquin valleys, in the Upper Sonoran Zone in the foothill districts, 
while in the southern Sierra Nevada it reaches through Transition and 
Canadian to the Hudsonian Zone. Rana boylii boyli/i in central Cali- 
fornia inhabits chiefly, if not exclusively, the Upper Sonoran Zone, 
entering the Transition Zone only locally ; in the northwestern humid 
coast belt it is present abundantly in both Upper Sonoran and Trans- 
ition ; ecologic conditions are favorable to the species in this area but 
unfavorable in the Transition Zone of the Sierra Nevada. 
The territory included in the several distributional areas men- 
tioned in the table is as follows : 
Northwestern coast, Del Norte, Humboldt, and northern Mendocino counties. 
Inner and central coast, western Siskiyou, Trinity, Lake, Napa, Sonoma, Marin, 
western Solano, western Alameda, San Francisco, San Mateo, western Santa 
Clara, and Santa Cruz counties. 
Southern coast, the coastal plain of southern California from Ventura County 
southward to San Diego County and eastward to the margin of the deserts, 
including the mountain ranges. 
Sacramento-San Joaquin valleys, the valley floors, below 400 feet altitude. 
Lower Sierra Nevada, the western slope of the range, between 400 and 7000 
feet altitude. 
High Sierra Nevada, that part of the range above 7000 feet, from Tuolumne 
County south to Kern County. 
Modoc region, northern Sierra Nevada-C’ascade system, and adjacent plateau, 
northward from Lake Tahoe and eastward from vicinity of Mount Shasta. 
Inyo region, Mono and Inyo counties. 
Mohave Desert, chiefly the desert portion of San Bernardino County. 
Colorado Desert, desert portions of Riverside, Imperial, and San Diego counties 
east of the mountains. 
Coastal islands, all of the islands from the Farallones south to San Clemente. 
Summarizing the data in the accompanying table, it will be seen 
that the northwestern humid coast belt includes most of the salaman- 
der population, one toad (which is relatively scarce), one hyla, and 
two frogs. 
Middle California, including the foothill and valley regions west 
of the high Sierra Nevada, has a population of from one to five species 
of salamanders, one spadefoot, one toad (two in a few places in south- 
ern California), one (or two) hylas, and two frogs. 
