946 16. CROTALIDA 
in front of the single pair of genials. Three or four rows of 
scales between supralabials and eye. Scales in 25 to 27 rows, 
keeled except in two or three rows on each side. Gastrosteges 
varying from 160 to 170. Anal not divided. Urosteges 
varying from 18 to 26, the first and a few of the posterior 
sometimes divided. 
The ground color is gray or light brown, marked along 
the back with a series of large dark brown blotches which 
tend to become cross-bands posteriorly. These blotches are 
paler centrally and are edged with black or very dark brown. 
Opposite these dorsal blotches are one or more series of 
smaller black or very dark brown lateral spots on scales from 
the first to fifth rows. Alternating with the dorsal blotches 
there may be a series of paler brown, more or less indefinite, 
blotches on scales of the fifth to eighth rows, and a series of 
smaller blackish spots on the first, second and third rows. 
The dorsal rhombs may be outlined with scales lighter than 
the ground color. The coloring of the head, as of the body, 
is similar to that of C. oreganus, but brighter. There is a 
light transverse streak on the supraocular in adults as well 
as young. The posterior part of the upper surface of the 
head usually shows an irregular pair of dark brown longi- 
tudinal streaks. A dark brown streak runs from the eye to 
and behind the corner of the mouth, the line of its lower 
edge striking the eye about under the pupil. This brown 
streak is bordered above a very narrow light streak, less than 
one scale wide, which passes above the corner of the mouth 
and forms the lower limit of the light temporal stripe. The 
tail is gray or brown with brown or dark gray rings or cross- 
bars, often more or less obscured. The lower surfaces are 
yellowish white, sometimes more or less clouded with brown. 
Length to anus.................252 578 608 658 720 725 
Length of tail to base of rattle 20 40 65 45 45 75 
