16. CROTALIDm 



Young specimens show a light transverse streak on the supra- 

 ocular, usually not present in adults. A dark streak runs 

 from the eye to the corner of the mouth, the line of its 

 lower edge striking the eye about under the pupil, although 

 a narrow forward continuation may be present. This dark 

 streak is bordered above by a light streak which is wider than 

 the width of one scale and passes above the corner of the 

 mouth. Another light streak crosses the side of the face 

 below the dark one and usually is bordered in front by a 

 dark brown patch on the side of the snout. Sometimes these 

 markings are more or less completely obscured. The tail 

 is provided with brown and light rings, a few of the former, 

 near the tip of the tail, being occasionally blackish. The 

 lower surfaces are white or yellow, more or less spotted or 

 clouded with brown. 



Some specimens are nearly black, and one from Utah is 

 pure white without any markings. 



Length to anus _. _... .__253 540 740 810 810 960 



Length of tail to base of rattle 22 35 43 64 85 77 



Distribution. — The Pacific or Black Rattlesnake occupies 

 all parts of California except the Colorado and Mohave 

 deserts. It ranges south into northern Lower California and 

 north across Oregon and Washington to British Columbia. 

 Farther east, it occurs in Idaho along the Snake River, and 

 has been taken in many parts of Nevada, in Utah, and in 

 Arizona. Throughout the northern part of this territory it 

 is the only rattlesnake, but in the southern regions is found 

 with other species. 



In California, it ranges from sea level up at least to an 

 altitude of 8,600 feet in the Sierra Nevada. Specimens have 

 been taken in San Diego (De Luz, Bonsall, San Diego, 12 

 miles northwest from San Diego, Julian, Dulzura, Cuyama- 

 ca Mountains, Orcutt, Witch Creek, Santa Ysabel, Campo, 



