170. Ventral plates before the anus 125 or more; rostral plate slightly separat' 



ing the internasals; loreal present; brown above, with a dark streak 

 along the center of each scale; belly white; Texas 

 Sonora taylori (Boulengcr) Taylor's Snake 

 (Contm taylori Boulenger) 

 Ventral plates before the anus less than 123; rostral plate almost or en' 

 tirely separating the internasals, which are each joined with an an' 

 terior nasal; no loreal; color either in cross bands or back brown, with 

 a dark dot at the posterior margin of each scale 171. 



171. Rostral plate not entirely separating the internasals; color above brown, 



with a dark dot at the rear margin of each scale; Lower Cal. 

 Ch^lomemscus stramineus Cope Dark Ground Snake 

 Rostral plate entirely separating the internasals; color above reddish, 

 with dark cross bands; Ariz, and Cal. 



Chilomeniscus cinctus Cope Red-and-black Ground Snake 



172. Normally with 15 to 17 rows of scales around the body 173. 

 Normally with 19 rows of scales around the body 220. 



173. Rostral plate abnormal (see below) 174. 

 Rostral plate normal 175. 



174. Rostral plate turned up at the end and entirely separating the inter- 



nasals above; back orange, with darker blotches or cross bands; belly 

 yellowish; Ariz, to Texas 



Ficimia cana (Cope) Dog'uosed Snake 

 Rostral plate flattened in front and partly free at the sides; internasals 

 partly in contact; back with a central yellow stripe, bordered on each 

 side by a dark stripe or a row of dark spots; belly yellowish; Utah to 

 Texas and Cal. 



Salvadora grahamiae B. & G. Patch-nose Snake 



175. No loreal; prefrontals projecting between the nasals and the preocular, 



reaching nearly or quite to the upper labials; color on back uniformly 

 brown; head darker; with or without a yellow ring or band at the 

 back of the head; semi-poisonous snakes with grooved poison fangs in 

 the back of the upper jaw 176. 



Loreal usually present; each prefrontal separated from the upper labials 

 by a scale squarely adjacent to its lower margin; color various 182. 



176. No light band across the back of the head 177. 

 Usually with a light band across the back of the head 179. 



177. Usually with six upper labials; head not much darker than the body; 



Mo. to Texas 



Tantilla gracihs B. 6? G. Slender Black-headed Snake 

 Usually with seven upper labials; head very dark 178. 



178. With less than 142 ventral plates; Okla. to Texas 



Tantilla \irnia Blanchard Oklahoma Black-headed Snake 

 With more than 144 ventral plates; Colo, to Texas and Ariz. 



Tantilla mgriceps Kennicott Western Black-headed Snake 



179. With the light band passing across the posterior ends of the parietals 180. 

 With the light band passing across the middle of the parietals 181. 



415 



