REPTILES OF THE PACIFIC COAST. 221 



Description. — Of moderate size. Head rather small, 

 flat-topped, varying in outline according to position of 

 fangs, etc. Kostral wider than high, in contact with 

 anterior nasal. Two nasals. Usually two preoculars 

 and four internasals. Supraocular large but not raised 

 into a horn-like process ; separated from its fellow by 

 five to seven irregular rows of scales. About fourteen 

 superior and thirteen to fourteen inferior labials ; first 

 pair of latter meeting in front of single pair of geneials. 

 Three rows of scales between labials and eye. Scales 

 in twenty-one to twenty-five rows, dorsals strongly 

 keeled. Gastrosteges varying at least from one hun- 

 dred and seventy-eight to one hundred and eighty-one. 

 Urosteges nineteen to twenty-one. 



The ground color is yellowish ash, varying from 

 whitish to tawny, marked along the back with a series 

 of rather small and indistinct brown blotches which 

 become cross-bars or stripes posteriorly (whence the 

 name tigris). These blotches are paler centrally than 

 about their edges and sometimes are nearly obsolete. 

 Smaller alternating blotches are present on the sides. 

 "The head markings are rather indistinct, especially 

 the postocular stripe, which is often lost in the dense 

 sprinkling of minute black dots covering the sides of 

 the head." The lower surfaces are yellow or white, 

 sometimes faintly clouded with brown. 



Length to arms 540 



Length of tail to rattle .35 



Distribution. — The Tiger Rattlenake " was formerly 

 only known from a few localities in southern Arizona 

 near the Mexican boundary, until in 1891 the Death 

 Valley exploration under Dr. Merriam extended its 

 range very materially into the desert mountains of 

 southern California and Nevada south of the thirtv- 



