1925 J Storer: A Synopsis of the Amphibia of California 
9 
Arizona, and New Mexico. The American deserts are believed to 
have evolved from an area that was much less arid in the recent past. 
A possible means of dispersal for the amphibians inhabiting desert 
areas, particularly canons, is indicated in the account of Hyla areni- 
color. The desert of southeastern California probably serves as a 
barrier to the spread of such a species as Bufo alvarius (the ‘river’ 
toad), which it would seem might be able to live in portions of the 
rivers of southwestern California, could it but reach that territory. 
Scaphiopus couchii now lives in southern Arizona and Lower Cali- 
fornia, but the desert of southeastern California (the Colorado Desert 
in particular) seems now to be too arid for the successful existence 
of this spadefoot there. Presumably it reached Lower California at 
a time when the Colorado Desert was less arid. 
Certain Salientia in California regularly spawn and their larvae 
develop in ponds where the content of alkaline salts is exceedingly 
high. In Death Valley Bwfo punctatus spawns in the alkaline waters 
from Texas Spring ; in the Santa Rosa Mountains adults of this species 
were found in a creek the water of which was laden to saturation with 
alkali. On Carrizo Plain, in San Luis Obispo County, transforming 
individuals of Scaphiopus hammondii w T ere collected in a pond the 
banks of which were encrusted with alkali deposited by the evaporat- 
ing waters. These high concentrations of lime and magnesium salts 
do not seem to be effective in checking amphibians. In certain parts 
of the deserts of southeastern California where there are alkaline lakes 
amphibians are lacking, but I believe that the controlling factor in 
such cases is lack of suitable shelter for the adults and not the high 
concentration of salts. 
Grinnell (1914, p. 252) has pointed out that, in the case of terres- 
trial birds and mammals, associational restriction of species is based 
upon three main items: (1) appropriate food supply, (2) presence 
of safe breeding places, and (3) presence of places of temporary 
refuge for individuals. As might be expected, the controlling con- 
ditions for amphibians, particularly the water-spawming species, are 
somewhat different. 
Amphibians generally seem to exercise little choice in the matter 
of food. This is particularly true among the Salientia, as shown by 
the great range of items found in the stomachs of toads. The kind 
of food taken seems to depend largely, if not solely, upon availability. 
