48. CROTALVS 



and eye. Scales in 25 to 29 rows, keeled except in one to 

 three rows of each side. Gastrosteges varying from 177 to 

 188. Urosteges 16to28. 



The ground color is grayish or yellowish brown, marked 

 along the back with a series of large darker brown blotches 

 which usually become cross-bars or incomplete rings post- 

 eriorly. These blotches are paler centrally than about their 

 edges, and vary greatly in shape and amount of separation. 

 Smaller alternating dark blotches are usually present on the 

 sides. Many of the scales between or around the dark dorsal 

 blotches are light, either gray or white. These colors some- 

 times show between the dark lateral blotches also. Many 

 specimens show a light transverse streak on the supraocular. 

 A dark streak runs from the eye to the corner of the mouth, 

 the line of its lower edge passing in front of the eye or 

 striking it about under its anterior corner. This dark streak 

 is bordered above by a light streak which is not wider than 

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

 mouth. Another narrow light streak crosses the side of the 

 face below the dark one, and is bordered in front by dark 

 brown on the side of the snout. The tail is provided with 

 brown and light rings or cross-bars, a few of the former, 

 near the tip of the tail, being sometimes blackish. The lower 

 surfaces are dull yellow or white, sometimes clouded with 

 brown. 



"The color varies greatly, being sometimes duller, some- 

 times brighter, lighter or darker, depending upon age, sea- 

 son, condition of skin, climate, and the predominating color 

 of surroundings."* 



Length to anus 595 



Length of tail to rattle 37 



Distribution. — "Broadly speaking, the Prairie Rattle- 



•Stejneger. Report U. S. Nat. Mus. for 1893. 



