CHECKLIST OF THE SNAKES OF MEXICO 15 



46. Internasal fused with anterior section of nasal ; a median light stripe, 



bordered laterally by darker lines; body elongate— Symphimus (p. 133) 

 Internasals normal 47 



47. No preocular ; anterior chin shields much enlarged ; no posterior chin 



shields Adelphicos (p. 30) 



One or two preoculars ; anterior chin shields, if separate, not greatly 

 enlarged; posterior chin shields generally distinct 48 



48. No loreal 49 



A loreal 53 



49. Snout much depressed, strongly projecting ; six supralabials ; one post- 



ocular; temporals 1-2 Geagras (p. 64) 



Snout normal ; six or seven supralabials, but if six, the temporals 1-1 ; 

 postoculars one or two 50 



50. Pattern of red, black, and usually yellow rings ; coral snakes 51 



Pattern not in rings 52 



51. A red instead of a black ring following yellow nuchal ring; maxilla 



with 2 teeth, a hollow fang followed by a smaller solid tooth ; black 

 rings 9 to 14 on body and tail, those on body almost as broad as red 

 rings and about twice as broad as yellow rings; red rings unmarked 



with black; snout all black Micruroides (p. 169) 



A black instead of a red ring following yellow nuchal or parietal ring; 

 maxilla with a single, hollow fang; pattern not as described. 



Micrurus (p. 169) 



52. Posterior maxillary teeth not grooved, not or scarcely enlarged ; uniform 



dark above, the color sharply differentiated from a light belly ; a 

 broken, light band about neck may be evident; ventrals 116 to 125; 



caudals 28 to 47 Tantillita (p 142) 



Posterior maxillary teeth deeply grooved, enlarged; color not as de- 

 scribed Tantilla (p. 134) 



53. A large, azygous scale following mental Dipsas * (part) (p. 49) 



No azygous scale following mental 54 



54. Caudal scales strongly tubercular; pattern of red, black, and yellow 



rings Procinura (p. Ill) 



Caudal scales not tuberculate ; pattern as described or not 55 



55. Supralabials 7-7 or less 56 



Supralabials 7-8 or more 59 



56. Two preoculars ; dark above, with a light neck ring_ Diadophis (part) (p. 46) 

 One preocular; no light neck collar or, if present, body not uniform 



dark above 57 



57. Posterior chin shields about equal to anterior ; size larger ; caudals 60 



or more Opheodrys (part) (p. 101) 



Posterior chin shields less than half size of anterior; size small, not 

 exceeding 300 mm. (12 inches) ; caudals 59 or less 58 



58. Abdomen rounded ; snout normal, not spadelike ; no nasal valve. 



Sonera (p. 126) 

 Ahdomen angled ; snout flattened, spadelike ; a nasal valve present. 



Chionactis (p. 35) 

 50. Head enlarged, much broader than the very slender neck; body and 

 tail very elongate, with over 200 ventrals and over 100 caudals. 



Imantodes (p. 75) 

 Head not enlarged, little broader than neck ; body and tail normal, with 

 less than 175 ventrals and less than 100 caudals Coluber ° (p. 37) 



• Dipsas sanniolus only. 



' Coluber oaxaca (Jan) only. 



