958 16. CROTALIDZ 
and tail, while the rest of the body is rested on the inter- 
vening loop, supporting the rest of the body, the weight 
then seems to be shifted to the head and tail and the rest 
of the body advanced, the whole progression being a series 
of graceful continuous movements. This seems to be the 
mode of progression.” 
Mr. Slevin found a pair mating under a bush on the 
desert west of Barstow, San Bernardino County, California, 
at about five o’clock in the afternoon, during the last week 
of April, 1913. 
219. Crotalus willardi Meek 
WILLARD’s RATTLESNAKE 
Plates 105 and 117 
Crotalus willardi, MEEK, Field Columb. Mus., Zool. Ser., Vol. 7, No. 1, 
1906, p. 18, pl. IIL (type locality, Tombstone, Arizona) ; 
Mocaquarp, Miss. Sci. au Mexique, Pt. III, Rept., 1909, p. 972; 
Hartman, Proc. U. S. Nat. Mus., Vol. 39, 1911, p. 569, fig. 1-4; 
Van DensurcuH & SieEvin, Proc. Cal. Acad. Sci., Ser. 4, Vol. 3, 
1913, p. 394; SreynecEeR & Barpour, Check List. N. Amer. Amph. 
Rept., 1917, p. 111; Swarru, Copeia, 1921, No. 100, p. 83 (type 
locality stated to be Hamburg, Ramsey Canyon, Huachuca, 
Mts., Arizona). 
Description—Moderately large. Head long, with 
flattened top and rather narrow, elevated snout. Rostral 
higher than wide, in contact with anterior nasal. Two nasals. 
Upper preocular large, not divided vertically. Internasals 
rather small, as long as wide, turned up anteriorly into the 
prominent canthus rostralis. Supraocular large but not 
raised into a horn-like process; separated from its fellow 
by about seven to nine irregular rows of scales. Supralabials 
13 to 15, separated from eye by about two rows of scales, 
Infralabials 13 to 15, first pair in contact on median line in 
front of a single pair of genials. Scales on body in 25 or 
