108 UNIVERSITY OF COLORADO STUDIES 



Crotalus cerastes Hallowell 



Horned Rattlesnake or Sidewinder 



Crotalus cerastes Hallowell, Proc. Acad. Nat. Set. Phila., p. 95, 1854. 

 Crotalus cerastes — Cope, Rept. U.S.N.M., p. 1190, 1898 (Colorado River, 

 Colo.). 



Dorsal scales in 21 rows, all excepting the first two or three rows 

 on each side heavily keeled; superior labials, n or 12; inferior labials, 

 12 or 13; supraocular plates elevated into a distinct "horn" on each 

 side; ventrals, 130 to 150; tail one-eighth to one-sixth of the total 

 length; size small, under three feet in length. 



Ground color yellowish, brownish or pinkish; ventral parts 

 yellowish ; dorsal pattern of thirty or more rounded blotches of dark 

 brown, separated and somewhat surrounded by grayish white; caudal 

 blotches forming rather distinct bands; a dark bar extending some 

 distance back of the eye; labial region light. 



This peculiar little rattlesnake is included in the Colorado fauna 

 on a very uncertain record. The true Colorado River does not flow 

 through Colorado although its headwaters are found in this state. 

 If "Colorado River, Colo.," refers to some of these headwaters this 

 record is valid, although it may be only an error. This snake should 

 be looked for, however, in the extreme southwestern portion of the 

 state. The name "Sidewinder" is given this little reptile because of 

 the peculiar sideways movements it often makes. It ranges through 

 Arizona, Nevada and southern Utah into California. 



Crotalus atrox Baird and Girard 

 Western Diamond Rattlesnake 

 Crotalus atrox Baird and Girard, Cat. N. Am. Reptiles, Pt. I, p. 5, 1855. 



Dorsal scales in 25 or 27 rows, all excepting the first and second 

 rows on each side, strongly keeled; superior labials, 16; inferior 

 labials, 15; ventrals, 170 to 190; top of the head flat; tail about 

 one-sixth of the total length. 



Ground color yellowish, brownish, gray or even slightly pink; 

 ventral parts yellowish, often somewhat clouded with gray or black, 



