912 16. CROTALIDH 
Description——Size large. Head broad, flat-topped. 
Rostral about as broad as high, in contact with anterior nasal. 
Two nasals. Two preoculars. Three postoculars. Inter- 
nasal and prefrontal region covered with large plates. Supra- 
ocular large but not raised into a horn-like process; separated 
from its fellow by from two to seven irregular scales. Four- 
teen to 18 superior and 15 to 20 inferior labials, first pair 
of latter in contact on median line in front of single pair of 
genials. Three to five rows of scales between supralabials 
and eye. Scales in 25 to 29 rows, keeled except in from two 
to four rows on each side. Gastrosteges varying from 180 
to 194. Anal not divided. Urosteges varying from 20 to 
27, a few of the first and last sometimes divided. 
The ground color above is yellow, or yellowish, grayish 
or brownish olive, marked along the back with a series of 
dark chocolate or olive brown blotches. These blotches 
often are irregular in outline and usually contain, on each 
side, a few scales of the light ground color. In some speci- 
mens the blotches are separated from each other or bordered 
by pale yellow scales. A peculiarity of the coloration is 
that each individual scale usually is of a uniform tint, but 
occasionally scales are particolored as in most other species. 
Smaller blotches may or may not be present on the sides be- 
low or between the dorsal rhombs. Posteriorly the general 
color becomes browner and the dark markings tend to be- 
come cross-bars which may show but little contrast with the 
darkened ground color. The rhombs on the neck often are 
confluent and many form longitudinal lines. The upper 
surface and sides of the head are of the same light ground 
color as the body. The internasal, prefrontal and supraocular 
regions are blackish brown. A dark brown band runs back and 
down from the eye to the scale above the last supralabial, 
often becoming indefinite or obsolete posteriorly. There 
usually is a trace of a similar dark band running down and 
