CHECKLIST OF THE SNAKES OF MEXICO 185 



Second infralabials separated from chinshields by backward prolonga- 

 tions of the first infralabials ; caudals in males more than 40, in fe- 

 males (probably) more than 35; rattles very small (less than 3.5 mm. 

 in adults) ; tail conspicuously attenuated; a middorsal series of sub- 

 rhombic blotches on a grayish brown ground stejnegeri 



4. Upper preoculars divided vertically, and the anterior section higher than 



the posterior and extended over the edge of the canthus rostralis in 

 front of supraocular ; body pattern of dark transverse bands less than 

 25 in number 4a 



Upper preocular not as described, usually single; or, if divided, more 



than 25 dorsal blotches or indistinct cross bauds on body 6 



4a. Supraocular markedly elevated ; dorsal spots 17 on body, not band- 

 like (except the extreme posterior), each 5 to 8 scale rows in width, 

 most about as long as broad ; caudals 20 in a male semicornutus 



Supraoculars normal; dorsal spots 14 to 23, all generally bandlike, 

 much broader than long when visible; caudals in males over 20 5 



5. A dark stripe from orbit to angle of mouth; a pair of separate occipital 



blotches ; body pattern of transversely expanded dark blotches or cross- 

 bands, interspaces frequently with secondary blotches or bands but 



little darker than ground color lepidus lepidus 



Dark stripe from orbit to angle of mouth obsolete or absent ; occipital 

 blotches united ; body pattern of conspicuous dark brown or black 

 crossbands, interspaces greenish gray or bluish gray with small dark 

 flecks or indistinct gray blotches lepidus klauberi 



6. Lower anterior border of orbit separated from supralabials by one scale 7 



Lower anterior border of orbit separated from supralabials by two or 



more scales 13 



7. One upper loreal"®; scale rows at midbody usually 23 or less 8 



Two upper loreals ; scale rows at midbody 27 or 25 ; upper margin of 



prenasals distinctly concave; head relatively long, narrow, and or- 

 nately marked; dorsal pattern of eight parallel series of circular or 

 elliptical dark brown blotches (median pairs sometimes fused) _ polystictus 



8. No lower loreals, upper loreal in contact with labials or, if separated 



from labials, the interposed scales are those entering the pit and the 

 nasal ; posterior section of nasal in contact with one or two labials ; 



scale rows 21-21-17 (15) 9 



One to three lower loreals intervening between upper loreal and labials; 

 posterior section of nasal not in contact with labials, or only with 

 first labial ; scale rows usually 23 or more anteriorly or medially, sel- 

 dom 15 posteriorly 10 



9. Ventrals 172 to 183, dorsal spots small, 51 to 60 ; lower preocular widely 



separated from loreal omiltemanus 



Ventrals fewer; dorsal spots fewer; lower preocular (sometimes trans- 

 versely divided) in contact with loreal or not 9a 



9a. Nasal In contact only with first supralabial ; loreal in contact with first 



and second supralabials ; dorsal spots 42, median, subquadrangular_ gloydi 

 Nasal in contact with first and second supralabials ; loreal separated 

 from supralabials ; dorsal pattern of transverse bands or transverse 

 rows of si)ots, typically none crossing the median line transversus 



10. Sixth or seventh supralabial below posterior edge of orbit ; pattern of 

 median blotches, but general color sometimes very dark or very light ; 



•* Scales lining anterior margin of pit are not regarded as loreals. 



