CHECKLIST OF THE SNAKES OF MEXICO 17 



78. Over half the subcaudals entire ; rostral somewhat enlarged. 



Rhinocheilus (p. 120) 

 All of subcaudals divided (rarely a few entire) ; rostral not or less 

 enlarged '^^ 



79. Anterior temporal single ; 19-17 scale rows ; no apical pits ; gray, with 



a series of brown cross bands Xenodon (p. 153) 



Two anterior temporals or more; apical pits present; if scale rows 

 19-17, pattern with red rings, with red, or nearly uuicolor 80 



80. Scale rows 27 or more Arizona (p. 32) 



Scale rows 23 or less 81 



81. Belly uniform, whitish, unmarked; uniform brownish above, or with 



alternating red and black bands or reddish with a black head and nape 

 and a light collar ; subcaudals 78 or more ; posterior maxillary teeth 



enlarged, grooved Oxyrhopus (p. 103) 



Belly checkered or otherwise marked with black; pattern not as de- 

 scribed ; subcaudals 79 or less ; posterior maxillary teeth not or little 

 enlarged, not grooved Lampropeltis (p. 77) 



82. No loreal ; prefrontals broadly in contact with two or three supralabials. 



Oxybelis (p. 101) 



A loreal or, if absent, prefront^s not as described 83 



S3. Two or more anterior temporals 84 



One anterior temporal 92 



84. Maximum scale rows near middle of body 17 or less 85 



Maximum scale rows near middle of body 19 or more 89 



85. Scale rows posteriorly 13 or less 86 



Scale rows posteriorly 14 or more 87 



86. A middorsal light stripe ; rostral frequently enlarged ; scale rows always 



17-13 Salvadora (p. 121) 



No middorsal light stripe, although lateral stripes may be present; 

 rostral never enlarged ; scale rows 17 or 15 medially— Masticophis (p. 92) 



87. Head short, broad, much broader than slender neck; body and tail very 



elongate and slender ; generally one preocular ; pupil vertical ; poste- 

 rior maxillary teeth enlarged, grooved ; dorsal pattern of broad 

 blotches; frequently vertebral scales somewhat enlarged. 



Imantodes (p. 75) 

 Head normal, little broader than neck; one or two preoculars; pupil 

 round ; posterior maxillary teeth not enlarged and grooved ; dorsal 

 pattern not in blotches in adults ; vertebral scales never enlarged 88 



88. Two preoculars Coluber (p. 37) 



One preocular Dryadophis (p. 52) 



89. Two or more loreals ; two or more preoculars ; posterior teeth grooved ; 



pupil vertical ; maximum scale rows 20-27 ; blotched. 



Trimorphodon (p. 145) 

 One loreal ; preoculars 1 or 2 ; posterior teeth not grooved or, if so, scale 

 rows 19; pupil round or vertical 90 



90. Maximum scale rows 25 or more Elaphe (p. 58) 



Maximum scale rows 23 or less 91 



91. No scale pits ; scale rows 19^17 ; striped or unicolor ; rear maxillary 



teeth enlarged and grooved Conophis (p. 43) 



Two scale pits ; scale rows seldom as low as 19-17 ; blotched or ringed ; 

 rear maxillary teeth not or slightly enlarged, not grooved. 



Lampropeltis (p. 77) 



