1925] Storer: A Synopsis of the Amphibia of California 19 
In general, the climatic features of a region may be diagnosed with 
some degree of success by a study of the amphibian fauna. Ran as 
develop best in areas well supplied with moisture; Bufos (or their 
analogues) are in the ascendancy in dry regions. The Rana : Bufo 
ratio in the total amphibian population (species x individuals) of a 
region is an indication of the region ’s relative moistness or dryness 
(temperature being excluded). 
There are no strictly stream-inhabiting Salientia in the eastern 
United States. In the west several species are closely related eco- 
logically to stream life, and other species make use of streams in the 
course of their life-histories. In the eastern states, at least in the 
northeastern portion of the country where lakes abound, there are 
numerous forms which dwell principally in ponds or in the marshy 
tracts adjacent to ponds. The streams of the northeastern states, with 
the break-up of winter, carry large quantities of broken ice and snow 
water. High water continues until well into the summer months. 
The large volume of water transported and the rather low temperature 
probably make it impossible for an amphibian to receive, in one season, 
a quantity of heat sufficient to accomplish growth and metamorphosis. 
But the ponds, as soon as they are free of ice, begin to absorb heat 
and this, together with the concurrent growth of aquatic micro- 
vegetation and insects, makes rapid growth possible for the larvae of 
amphibians which spawn there. 
In contrast to the preceding there are no less than five Salientians 
in the western United States which, for one reason or another, as will 
be discussed in the chapters on species, are inhabitants of streams. 
These are Ascaphus truei, Bufo alvarius, Hyla arenicolor, Rana b. 
boylii, and Rana b. muscbsa. The lake or pond habitat here is used by 
Ambystoma calif or niense, Bicamptodon ensatus, Rana boylii sierrae, 
and Rana aurora draytonii. 
DISTRIBUTION OF AMPHIBIA IN CALIFORNIA 
The amphibian fauna of California is found to be widely different 
from that of eastern North America. Only one or two of the species 
west of the crest of the Sierra Nevada have any very close affinities 
with species east of the Great Plains. Rana pipiens, the most widely 
distributed species of frog in North America, reaches the eastern 
border of the State ; it, however, does not enter the real California 
