REPTILES OF THE PACIFIC COAST. 223 



feebly keeled except in one to three lower rows on sides 

 where smooth; those near middle of back with central 

 tubercular swellings. Gastrosteges varying at least from 

 one hundred and thirty-four to one hundred and forty- 

 six. Urosteges sixteen to twenty-one, a few sometimes 

 divided. 



The general color above is gray, often with a yellow- 

 ish or vinaceous tinge, with a series of rather small and 

 indefinite blotches of gray- 

 ish or yellowish brown. 

 Smaller blotches or spots 

 are usually present on the 

 sides and on the tips of 

 the gastrosteges. The su- 

 praocular shows an indis- 

 tinct transverse streak. A brown streak runs from the 

 eye to the corner of the mouth. The tail is ash-color 

 with half rings of brown, which are much darker near 

 its tip than anteriorly. The lower surfaces are yellow- 

 ish white, sometimes faintly clouded with brown or 

 gray. 



Length to anus 415 440 450 



Length of tail to rattle 38 42 31 



Distribution. — The Sidewinder occupies the lower lev- 

 els of the Colorado and Mojave Deserts, where the Tiger 

 Rattler occurs in the mountainous districts, and ranges 

 thence across western Arizona and southern Nevada to 

 "southwestern Utah." In California it has been taken 

 near Salton, in the Colorado Desert; at Lone Pine, in 

 Owen's Valley; in Panamiiit Valley; at Borax Flat; at 

 Bennett Wells, Death Valley; and at Pilot Knob. It is 

 known to occur in Nevada in Pahrump, Vegas, and In- 

 dian Spring Valleys, at Sarcobatus Flat, in the Amar- 

 gosa Desert, and in the valleys of the Virgin and Lower 

 Muddy. 



