16. CROTALlUm 



XXIII, XXVIII, fig. 2; Strecker, Baylor Bulletin, Vol. XVIII, 

 No. 4, 1915, p. 45; Stejneger & Barbour, Check List N. Amer. 

 .Amph. Rept., 1917, p. 109; Vorhies, Univ. Ariz. Agric. Exper. 

 Station Bull. No. 83, 1917, p. 359. 



Description. — Size small. Head broad, flat-topped, 

 with rather narrow snout. Rostral about as high as wide, in 

 contact with anterior nasal. Two nasals, sometimes united. 

 Two preoculars. Two or three postoculars. A large scale 

 just in front of supraocular. Supraocular large, but not 

 raised into a horn-like process; separated from its fellow by 

 about three to five irregular rows of scales. Eleven to 14 

 superior and 10 to 12 inferior labials, first pair of latter in 

 contact on median line in front of single pair of genials. One 

 to three rows of scales between supralabials and eye. Scales 

 in 21 to 23 rows, keeled except in two or three rows on each 

 side. Gastrosteges varying from 153 to 169. Anal not 

 divided. Urosteges varying from 18 to 31. 



The color above is a greenish or bluish or ashy gray with 

 about 1 7 to 19 dark brown or black blotches or cross-bands 

 between the head and anus. These dark markings are sep- 

 arated along the middorsal line by intervals from two to five 

 times their own length along that line. They may extend 

 laterally to the gastrosteges, or may be divided laterally 

 into spots. Their outlines usually are irregular or serrate. 

 The scales at their margins are often spotted with very dark 

 brown or black, and similar spots are scattered sparsely 

 through the gray intervals. The scales of the first two or 

 three lateral rows may be tinted with salmon pink or orange. 

 The head is of the gray ground color, minutely dotted with 

 blackish brown, but without definite dark markings. The 

 lower surfaces are yellowish white, more or less clouded with 

 brown or gray. The tail is gray proximally, orange or sal- 

 mon distally both above and below, crossed by from two to 

 four brown bars or rings. 



