MORPHOLOGY OF VENOMOUS SNAKES 45 



Crotalus tigris Kennicott. " Tiger Rattlesnake." 



This snake seldom attains more than 3.5 feet. The general features not essen- 

 tially different from prairie and Pacific rattlesnakes. Yellowish-gray, with a series 

 of small and not very distinct blotches on back and on each side, for the anterior 

 third of body; on the latter two-thirds, these blotches fuse into regular crossbands, 

 producing a strongly barred effect. It becomes docile in captivity. Desert moun- 

 tains of Arizona, Nevada, and southern California. 



Crotalus molossus Baird and Girard. " Black-tailed Rattlesnake." 



Head large and quite blunt at snout. On the upper part of snout are 3 pairs 

 of enlarged scales. Body fairly stout and attains a length of 3.5 to 5 feet. The 

 uniform jet-black tail distinguishes this snake from the other southwestern species. 

 Its range is not farther north than the central portion of Arizona. Its range into 

 Mexico is not definitely known. 



Crotalus cerastes Hallowell. " Horned Rattlesnake " or " Side Winder." 



One of the smallest species of Crotalus. It has a horn-like projection over each 

 eye. Body stout, with strongly keeled scales. Pale brown, yellow, or pinkish, 

 with a series of dull blotches, generally separated by white interspaces; irregular 

 rows of small black or brown spots on sides; several black bars on tail. Maximum 

 length about 2.5 feet. Desert areas of Arizona, southern Nevada, southwestern 

 Utah, and eastern California. 



Crotalus lepidus Kennicott. " Green Rattlesnake." 



The smallest species of the genus. Body quite slender. Greenish-gray or rich, 

 dark green above, crossed at wide intervals by narrow jet-black bands; the bands 

 are usually bordered with pale greenish-yellow; belly pinkish, or yellowish- white 

 Just behind the head is a black blotch forked in the front. Length about 2 feet. 

 This species inhabits mountainous areas, on both sides of the Mexican boundary. 



Crotalus pricei Van Denburgh. 



Rare and very small, resembling Sistrurus catenatus in general appearance. 

 Length about 2 feet. Southern Arizona to northern part of Mexico. 



Crotalus triseriatus. 



Length about 2 feet. Mexico. 

 Crotalus polystictus. 



Length about 2 feet. Tableland of Mexico. 



Crotalus mitchelli Cope. " White Rattlesnake." 



The head squamation differs from the other rattlesnakes. The large anterior 

 nasal plate is separated from the rostral plate by small scales. With other species 

 of Crotalus the anterior nasal shield is in contact with the rostral plate. Grayish- 

 yellow or pinkish, the body profusely sprinkled with brown dots; upon the back 

 these dots assume the form of a series of blotches, which imparts much the same 

 effect as the pattern of the western diamond rattlesnake. A bright-red specimen 

 has been taken in Canyon Prieto of Arizona and was named Crotalus pyrrha by 

 Cope, but no more of the same variety have since been encountered. Length 

 about 3.5 feet. Desert mountains of lower California, southern California, southern 

 Arizona, and extreme northeastern Mexico. 



Crotalus terrificus. " Dog-faced Rattlesnake." 



Length 4 to 4.5 feet. Northern part of Brazil and northern Argentine. 



