SERPENTS. 



399 



by having the nasal plates divided ; four prefrontals ; eighteen labials ; seventeen 

 inf ralabials, and the scales in twenty-four rows. The body is yellowish, sti-ongly marked 

 with a dorsal series of rhombs, similar to those of C. adamanteus. An allied species 

 collected at Fort Whipple, measuring thirty-one inches in length, contained an adult 

 blue-bird, Sialia mexicana. They are reported from the San Francisco mountains 

 at an elevation of 10,000 feet, and inhabit dry rocky ground. C. confluentus, the 

 prairie rattle-snake, is very abundant along the Missouri River and its tributaries from 

 Nebraska to the Rocky Mountains. During the hot season they retire to the dry 

 canons, where they hide among the willows, being extremely sluggish and stupid, and 

 possibly partially blind, as the cuticle, though cleaving from the, body and eyes, is not 

 as yet shed. The head is sub-triangular, and the plates irregular, angulated, imbri- 



FlG. 230, — Crotatus durissus. rattle-snake. 



cated, and not infrequently tuberculated. The labials are from fourteen to eighteen 

 above and below, and the scales of the body are arranged in fi-om twenty-five to 

 twenty-nine rows. Along the back there are between forty and fifty brown spots 

 margined with narrow white lines. C. polysiictus, inhabiting the table-lands of 

 Mexico, seldom reaches the length of two feet. There are two nasals, two loreals, 

 fourteen labials, and thirteen infralabials ; and, of the twenty-seven rows of scales, all 

 are keeled excepting the lower two. Along the back is a median yellowish stripe bor- 

 dered by lines of grayish brown, and ornamented by a series of seven brownish black 

 spots. 



C. lucifer, the western black rattle-snake, was brought to the light of science in 

 1852, by the description of Baird and Girard from sj^ecimens captured by members 

 of the exploring party under Cairtain Chas. Wilkes in California and Oregon. The 



