1925] Storer: A Synopsis of the Amphibia of California 163 
species. The sandy texture of the soil in many places and the fact 
that rain pools seldom form there are possibly the excluding factors. 
The presence of alkali sinks indicating the former occurrence of lakes 
in that region has been taken by some climatologists to mean that a 
cycle of increasing aridity is claiming the region, in which event con- 
ditions on those areas are growing less and less favorable for am- 
phibians, even of the extreme type of Scaphiopus. The species prob- 
ably occurred there when the lakes were in existence, as alkali alone, 
even in high concentration, does not seem to be a deterrent to this 
spadefoot. 
Bufo alvarius Girard. Colorado River Toad 
(Pi. 12, fig. 32) 
Bufo alvarius Girard in Baird (1859a, p. 26, pi. 41 [figs. 1-6]). Original 
description, type from Yalley of Gila and Colorado [— Fort Yuma, Cali- 
fornia; see Cope, 1889, p. 267]. 
Bufo alvarius, Cooper (1868, pp. 485-486; 1869, p. 480). Colorado River 
Yalley. 
Bufo alvarius, Cope (1889, pp. 265-267, text fig. 62). General account. 
Bufo alvarius, Dickerson (1906, pp. 106-108, col. pi. 5, pis. 36, 37). Gen- 
eral account. 
Bufo alvarius, Camp (1915, p. 509). Colorado River Yalley. 
Bufo alvarius, Grinnell and Camp (1917, p. 144, fig. 4). Range in Cali- 
fornia. 
Bufo alvarius, Stejneger and Barbour (1917, p. 26; 1923, pp. 23-24). 
General range. 
Diagnosis. — Size very large, largest of the north American 
bufonids, head-and-body length up to 130 millimeters (5% inches) 
(Ruthven [1907, p. 505] lists a specimen 147 mm. long) ; skin smooth 
and leathery ; warts on body small, low, and scattered ; cranial crests 
curved around eyes; parotoids long and divergent posteriorly; large 
raised 'warts’ or glands on exposed surface of femur and tibia. 
Comparisons. — Distinguished from other California Salientia (ex- 
cept Bufonidae) by large size and presence of distinct parotoid glands 
on shoulder region ; from all other California Bufonidae by large size, 
curved cranial crests, very smooth skin, and large glands on femur 
and tibia. 
Description. — Size very large, general build stout, head and body 
depressed. Outline of head from above, acuminate oval, muzzle 
bluntly rounded in profile, tip flat-topped; canthus rostralis very 
distinct, slightly shorter than length of orbit; external nares nearly 
terminal, below canthus rostralis ; orbit rounded ; eyelids thick ; inter- 
orbital space about three-fourths length of orbit ; each cranial crest a 
single curved ridge paralleling median and posterior margins of orbit, 
ending just above tympanic membrane ; preorbital crest straight ; occa- 
sionally a transverse postorbital crest between tympanum and orbit; 
