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. 
FHabits.—One specimen contained an adult ground squir- 
rel. 
