REPTILES OF THE PACIFIC COAST. 217 



marked along the back with a series of large dark brown 

 blotches which become cross-bars or incomplete rings 

 posteriorly. These blotches are often paler centrally 

 than about their edges and vary greatly in shade, shape, 

 amount of separation, and contrast with the ground 

 color. Smaller alternating blotches are usually present 

 on the sides. Many of the scales between or around the 

 dark dorsal blotches are light — yellow, gray, or white. 

 These colors often show between the lateral dark blotches 

 also. Young specimens show a light transverse streak 

 on the supraocular, 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 narrow forward continuation 

 may be present. This dark streak is bordered above by 

 alight 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 mark- 

 ings are more or less completely obscured. The tail is 

 provided with brown and light rings, a few of the for- 

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

 The lower surfaces are white or yellow, more or less 

 spotted or clouded with brown. 



Length to anias -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 

 Mojave Deserts. It ranges across Oregon and Washing- 

 ton to British Columbia. Farther east, it occurs in 

 Idaho, along the Snake River, and has been taken in 



