16 University of California Publications in Zoology |Vou-9 
the head of a horned lizard protruding through the body wall. 
Mr. Newhall witnessed such a phenomenon in the Yosemite 
Valley. Rattlesnakes have also been found with the horns of 
a Phrynosoma caught in the throat (Cope, 1898). With the 
coming of civilization the domestic cat becomes a formidable 
enemy second only to the curio collector, who has practically 
exterminated the horned lizards in some localities. 
A Phrynosoma is slow and sluggish in its movements. If 
moving leisurely along, it drags its body on the ground, but 
when running stands well on its legs. When frightened, it 
usually tries to seek shelter in a nearby bush or buries itself 
in the sand. The latter operation is very interesting, for it is 
so widely different from the method used by other burrowing 
animals. The chisel-shaped head is the principal tool, the legs 
being used almost solely for forcing the head forward. <A 
wriggling motion of the head and body serves to drive the head 
beneath the sand and soon covers the body completely with earth. 
A little shake of the tail flings the dirt over that appendage 
and the lizard becomes entirely hidden. The nostrils are kept 
either at the surface of the ground or near enough to the surface 
so that breathing is possible. 
The members of this genus, like most of the Lacertilia, are 
such lovers of sunshine and heat that they are seldom found 
in winter or on cold or rainy days. The winter months are 
spent in hibernation in rodent holes or buried beneath the soil. 
A specimen of P. blainvilled blainvillei, plowed out on December 
15, 1909, was found to be in a state of hibernation. The eyes 
were tightly closed and the lizard could not be induced to open 
them; the muscles were set, the animal often lying in a very 
awkward position. The breathing was slow and erratic, inter- 
vals of several minutes intervening between inspirations. The 
external temperature of the body was about that of the air 
(15° to 18° C.). Some ten minutes after placing the lizard in 
the sun, it showed signs of renewed energy and was ready to 
run at anyone’s approach. 
Ants, beetles, flies, and other insects form the principal diet, 
although Bell (1828) states that P. douglassi is somewhat her- 
bivorous. Unless very hungry, live insects alone satisfy a 
