48. CROTALUS 917 



Remarks. C. atrox is closely related to C. tortugensis, 

 C. exsul and C. lucasensis. It differs from both in the more 

 faded, pepper-and-salt style of its coloration. It may some- 

 times be pinkish along the lower rows of scales but seems 

 never to develop the red coloration of C. exsul. In C. exsul 

 the first labial usually is divided into a labial and an inferior 

 portion. This occurs in only two of 20 specimens of C. atrox 

 from Arizona. The largest specimen I have seen measured 

 five feet four inches. It was secured at Yuma, Arizona. 



Distribution. The Desert Diamond Rattlesnake ranges 

 from Texas west to the deserts of southern California, and 

 south into Sonora (Camora), and probably northeastern 

 Lower California. It has been taken on Tiburon Island. 



In Arizona, it is the common rattlesnake of the lower 

 levels, and has been collected at Fort Buchanan, Santa Cruz 

 County; Fort Huachuca and Wilcox, Cochise County; Tuc- 

 son and the Catalina Mountains, Pima County; Fort Grant, 

 Graham County; Rice, Gila County; Cave Creek and Phoe- 

 nix, Maricopa County; Vicksburg and Yuma, Yuma County; 

 and about 15 miles south of Hackberry, Mohave County. 



California records are few in number. It has been taken 

 at Fort Yuma and Laguna Station, Imperial County, and 

 near Coachella and Mecca, Riverside County. 



I believe that this species has not yet been secured in 

 Lower California, but it undoubtedly occurs in the north- 

 eastern part of the peninsula. Lower California records are 

 based upon specimens of C. lucasensis and C. exsul. 



Habits. One specimen contained an adult ground squir- 

 rel. 



