End of snout indistinctly keeled; no light bar on rostrum; tail dark or 

 barred 28. 



28. With a vertical division in the upper preocular; snake greenish, with 



narrow, widely separated, dark cross bars along entire length 29. 



Upper preocular entire; coloration not so 30. 



29. With a dark line from the eye to the corner of the mouth; Texas 



Crotalus lepidus lepidus (Kennicott) Rock Rattlesnake 

 No dark line from the eye to the corner of the mouth; Ariz, and N. M. 

 Crotalus lepidus \lauberi Gloyd Green Rattlesnake 



30. With several internasals (between the nasals and behind the rostrum) 31. 

 With two internasals 36. 



31. With a dark band passing obliquely backwards on each side of the head 



from below the center of the eye to about the corner of the mouth; 

 with light streaks before and behind this dark band about one scale 

 wide 32. 



With a dark band passing obliquely from behind the center of the eye to 

 about the corner of the mouth; with light streaks before and behind 

 this band about two scales wide 33. 



32. General color usually brownish'green; Iowa to the Rockies 



Crotalus viridis viridis Raf. Prairie Rattler 

 (Crotalus confluentus confiuentus of Cope) 

 General color usually reddish'brown; Ariz, and Utah 



Crotalus viridis nuntius (Klauber) Arizona Prairie Rattler 



33. Ground color brown, with very dark dorsal blotches and a series of small 



dark blotches along each side, or sometimes almost completely dark; 

 Idaho to Ariz, and westward 



Crotalus viridis oreganus (Holbrook) Pacific Rattler 

 (Crotalus confiuentus ludfer of Cope) 

 General color reddish or yellowish, with lateral blotches obscure or ab' 

 sent 34. 



34. Adults reddish, with indistinct blotches; Grand Canyon, Ariz. 



Crotalus viridis abyssus (Klauber) Grand Canyon Rattlesnake 

 Adults yellowish 35. 



35. Adults pale yellowish, with obscure blotches; seldom over two feet long; 



Wyo. to Colo, and Utah 



Crotalus viridis concolor (Woodbury) Faded Rattlesnake 

 (Crotalus viridis decolor (Gloyd) ) 

 Adults yellowish'brown, with more distinct blotches; getting to be over 

 two feet long; Idaho to Ariz, and Cal. 



Crotalus viridis lutosus (Klauber) Yellow Rattlesnake 



36. With blotches anteriorly and with cross bands on back and sides along 



posterior two-thirds of body, or sometimes entirely dark 37. 



Back usually with blotches along most of length; no cross bands 39. 



37. Rostral plate as wide as or wider than high; snake grayish, with blotches 



on first third of body and narrow, regular bands posteriorly; tail 



395 



