4-8. CROTALUS 913 



back from the pit. The lower surfaces are white or pale 

 yellow often clouded or mottled with gray or brown on the 

 body, especially posteriorly and laterally. The tail both above 

 and below is black or blackish brown, sometimes unicolor, 

 but often with some lateral paler areas indicating cross- 

 bands. 



Length to anus-_ 615 796 800 896 905 1070 



Length of tail to base 



of rattle 45 45 65 54 54 76 



Distribution. The area inhabited by this large species 

 extends from Pecos and El Paso counties, Texas, west to 

 Arizona, and south into northern Mexico. 



In Arizona, this rattlesnake is quite common in the Hua- 

 chuca Mountains, in Cochise County, where it has been 

 taken in Ramsey, Miller and Carr canyons. It has been 

 collected also at an elevation of 5,000 feet near Blue River, 

 Greenlea County, and at an altitude of 6,000 feet in Wal- 

 nut Canyon, in the Santa Rita Mountains. Specimens are at 

 hand from Saw Mill Canyon, Santa Rita Mountains, Pima 

 County; trail between Gardner Canyon and Greaterville, 

 Pima County; Tucson, Pima County; vicinity Pete Moun- 

 tain, Santa Rita Range, Santa Cruz County; Fort Buchanan, 

 Santa Cruz County; and from the canyon between Madera 

 and Agua Caliente canyons, Santa Rita Mountains, Santa 

 Cruz County, Arizona. The most northern record seems to 

 be that of a specimen secured at Cave Creek, Maricopa 

 County. Cope has recorded a specimen as taken by Dr. 

 Mearns in the "Tucson Mountains, Yuma County," probably 

 an error for Pima County. 



Remarks. This species is easily distinguished by its 

 black tail and snout, and by the large plates on the anterior 



