AMPHIBIA AND REPTILIA OF COLORADO 109 



especially near the lateral margins of the ventrals; dorsal pattern of 

 thirty to forty or more, hexagonal to diamond-shaped blotches of black 

 or dark brown, each blotch emarginate with ashy white and with more 

 or less of the ground color in its center; tail ashy white, crossed by 

 three to six black or very dark brown rings which are open ventrally; 

 head without the vertical white stripe under the nostril which is present 

 in C. adamanteus (Beauvais), the eastern Diamond-Back Rattlesnake. 

 Length, up to seven feet. This rattlesnake ranges from the 

 middle of Texas west to Arizona. In southern California it is repre- 

 sented by a red subspecies, C. atrox ruber Cope. 



Colorado Specimen. — ^We include this rattlesnake in the fauna of Colo- 

 rado on the record kindly given us by Mr. L. J. Hersey of the Colorado Museum 

 of Natural History in Denver. This specimen, determined by Mr. Hersey, was 

 five and one-half feet in length and was collected at Trinidad, Colo., by William 

 Wilson, August 17, 1912. 



Crotalus confiuentus Say 

 Prairie Rattlesnake {Figures 38, 39 and 40) 



Crotalus confiuentus Say, Long's Exped. Rocky Mts., Vol. II, p. 48, 1823 

 (probably near junction of Fountain Creek and the Arkansas River). 



Crotalus confiuentus confiuentus — Yarrow, U.S.N.M. Bull. 24, p. 77, 1882 

 (Cache la Poudre River); Cope, Rept. U.S.N.M., p. 11 72, 1898 (Cache la Poudre 

 River) . 



Dorsal scales in 27 or 29 rows, all strongly keeled, excepting those 

 of the first two or three rows on each side; superior labials, 15 or 16; 

 inferior labials, 16 to 18; ventrals, 170 to 190; top of the head flat 

 or very slightly concave; tail about one-sixth of the total length. 



Ground color greenish yellow, gray or brown; ventral parts yel- 

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

 brown, distinctly darker around the edges and outlined with yellowish 

 white; pattern more obscure toward the tail; a dark bar extending 

 from just below the middle of the eye to the posterior angle of the 

 mouth, bordered on each side by a yellow stripe one row of scales wide; 

 two dark spots in the occipital region; two more or less distinct 

 yellowish stripes on each supraocular plate; an irregular row of spots, 

 often rather indistinct, down each side of the body. 



