646 13. COLVBRW& 



eee. Rostral very large, with free lateral edges; 

 coloration in spots, and blotches. 



Phyllorhynchus. p. 692. 



eee 1 . Rostral normal, without free edges; colora- 

 tion in blotches, 

 fff. Gastrosteges fewer than 200. 



Hypsiglena. p.779. 



fff. Gastrosteges more than 200. 



Trimorphodon. p. 884. 

 b*. Anal plate single. 



cc. Urosteges in one series (at least anteriorly). Snout 

 protruding; coloration in cross-bands. 



Rhinocheilus. p. 773. 

 cc'. Urosteges in two series. 



ddd. Scales in 21 to 23 rows; loreal nearly as high 

 as long; rostral not protruding; coloration in 

 rings, blotches, or lines. 



Lampropeltis. p. 740. 



ddd'. Scales in 27 to 31 rows; loreal elongate; 

 rostral prominent; coloration in blotches. 



Arizona. p. 701. 

 a'. Dorsal scales keeled. Laterals keeled or smooth; 



urosteges in two series, 

 bb. Anal plate single. 



ccc. Prefrontals normally four (often two); scales in 

 27 to 35 rows, several of the lower usually smooth; 

 no longitudinal lines. 



Pituophis. p. 70 5. 



ccc'. Prefrontals two; scales in 17 to 23 rows; not more 

 than three smooth; usually with longitudinal 

 lines, sometimes spotted or unicolor. 



Thamnophis. p. 787. 

 bb'. Anal plate divided, 

 cccc. Pupil round; rostral not free at edges. 



