48. CROTALUS 957 
right out in the noonday sunshine of mid-summer. In 
neither case were the snakes easily seen, as they were of the 
exact color of their sandy surroundings. Both, though alert 
allowed themselves to be noosed without moving away or 
doing more than rattle feebly. 
Specimens which I have seen had eaten lizards, Uta 
stansburiana, Cnemidophorus tigris and Phrynosoma platy- 
rhinos. The Phrynosoma had been only partially swallowed; 
and its horns had penetrated and protruded from the ventral 
surface of the snake’s neck. 
Regarding the mode of progression of this species Mr. 
Cowles notes: “These snakes seem to be almost entirely 
restricted to the sandy areas of the desert, rarely wandering 
from them, and then only for a short distance, its mode of 
locomotion admirably fits it for the type of country which it 
inhabits. The ordinary snake finds difficulty in rapid motion 
over the loose and shifting sand, since part of the tractive 
power comes from a bracing of each loop of the body against 
that part of the ground which is posterior to the loop, and 
through the movement of the central portion of the body 
against the surface of the ground. It can readily be seen 
that a shifting and loose surface would seriously hinder the 
progress of the ordinary snake. The “Side-winder,” Crota- 
lus cerastes, instead of progressing as do ordinary snakes, 
longitudinally, progresses laterally, leaving separate tracks, 
each paralleling the other, and angling in the direction in 
which the snake is moving. Each track is approximately the 
length of the snake making it, and is wavy, that is a series 
of “S” shaped loops. The tracks give no sign of any part 
of the body moving from one mark to the other, which gives 
the impression that the snake jumps the three to six inch inter- 
val between the tracks. Such is not the case, however. When 
the snake is moving, the body is kept partially looped and 
the advance seems to be through the advancing of the head 
