158 CALIFORNIA ACADEMY OF SCIENCES. 



i''. — Temporals 2-2 (rarely 1-1 or 2-3); frontal much 

 longer than broad; no single, definite, light collar 



on neck Bascanion. — p. 183. 



P. — Rostral large, with free lateral edges; coloration in longitu- 

 dinal bauds Salvadora. — p. 180. 



e^. — Pupil vertically elliptical. 



Eostral without free edges; coloration in blotches. 



Hypsiglena. — p. 178. 

 b''. — Anal plate single. 



j. — Urosteges in one series (at least anteriorly). 

 Snout protruding; coloration in cross-bands. 



Rhinocheilus. — p. 174. 

 p. — Urosteges in two series. 



k. — Scales in twenty-one to twenty-three rows; loreal nearly as 

 high as long; rostral not protruding; coloration in rings, 



blotches, or lines Xiampropeltis. — p. 166. 



k^. — Scales in twenty-seven to thirty-one rows; loreal elongate; 

 rostral prominent; coloration in blotches. 



Arizona. — p. 192. 

 a'^ — Dorsal scales keeled. 



Laterals keeled or smooth; anal single; urosteges in two series. 

 1. — Prefrontals normally four (often two); scales in twenty-seven to 

 thirty-five rows, several of the lower usually smooth; no longitudinal 



lines Pituopliis. — p. 195. 



1-' — Prefrontals two; scales in seventeen to twenty-three rows; not more 

 than three smooth; usually with longitudinal lines. 



Thamnophis. — p. 199. 



Genus 24. CHILOMENISCUS. 



Chilomeniscus, Cope, Proc. Ac. Nat. Sci. Phila., 1860, p. 339 (type 

 stramineus). 



The body is stout and cylindrical, with short tail, and 

 without constriction at neck. The snout protrudes far 

 beyond the lower jaw and is rounded and greatly de- 

 pressed. The internasal is merged in the anterior nasal 

 which, therefore, extends onto the top of the snout. 

 There is a small posterior nasal but no loreal. The 

 scales are in thirteen rows, smooth and with apical pits. 

 The anal plate is divided, and the urosteges are in two 

 series. The eye is small, with round pupil. 



