180. Dark band on neck (behind the light band) not more than one and one 



half scales wide; Ariz;. 



Tantilla wilcoxi Stejneger Wilcox's Black'headed Snake 

 Dark band on neck two to four scales wide; Va. southwards 

 Tantilla coronata B. & G. Crowned Snake 



181. Dark color of head spreading on to the throat; Cal. 



Tantilla eiseni Stejneger Ringed Black-headed Snake 

 Dark color of head not spreading below the mouth; Okla. to Texas and 

 Ariz. 



Tantilla atriceps (Giinther) Light'chinned Black'headed Snake 



182. No preocular plates; prefrontal plates bordering eyes; back brown, with 



or without two rows of small dark dots; belly yellow 183. 



With one or more preoculars; prefrontals not bordering eyes; color var' 



ious 184. 



183. With 15 rows of scales; N. J. to Ohio, southward to S. C. 



Haldea valenae valeriae (B. £s? G.) Eastern Ground Snake 

 With 17 rows of scales; Ind. to Texas 



Haldea valeriae elegans (Kennicott) Western Ground Snake 



184. Nostril situated in an ungrooved, single nasal plate 185. 

 Nostril between two plates or in one plate which is vertically grooved 



below the nostril 193. 



185. Back grass green; belly whitish; with more than 66 pairs of plates be- 



neath the tail; N. D. to N. M. and eastward 



Opheodrys vernalis (Harlan) Smooth Green or Grass Snake 

 (Liopeltis vernalis (Harlan) ) 

 Color not so; with less than 62 subcaudals 186. 



186. Color reddish-brown above, usually with a faint lengthwise stripe along 



the fourth or fifth row of scales up on each side; plates of belly yel- 

 lowish, with dark front borders; West Coast 



Contia tenuis (B. &' G.) Pacific Ground Snake 

 Back color various; belly plain light colored or with dark cross bars which 

 form rings around the body 187. 



187. Snout much flattened and extending well beyond lower jaw; sides of 



belly angled; with dark cross bands; Nev., Ariz;., and Cal. 



Sonora occipitalis (Hallowell) Ringed Ground Snake 

 Snout and belly normally curved 188. 



188. Ventral plates usually less than 154 in males, 166 in females; with or 



without dark cross bands 189. 



Ventral plates usually more than 154 in males, 162 in females; with or 



without dark cross bands 190. 



189. Males with 52 or less pairs of subcaudal plates, females with less than 



45 ; Kansas, Colo, and southwards 



Sonora episcopa (Kennicott) Brown Ground Snake 

 Males with 53 or more pairs of subcaudal plates, females with more than 

 45; southwestern Texas 



Sonora semiannulata hlanchardi Stickel Blanchard's Ground 

 Snake 



416 



