CHECKLIST OF THE SNAKES OF MEXICO 159' 



8. No stripes; nearly uniform grayish olive above digueti 



Lateral light stripes conspicuous ; dorsal dark spots distinct, a black 



crescentic neck mark hammondii 



9. Usually anterior edges of ventrals black, and the entire belly clouded, 



but never a longitudinal dark line or entire belly black ; chin and 

 sometimes subcaudal surface cream, sharply differentiated from dark 



belly color 3^ 



Not so ; belly unmarked or with a longitudinal dark line, or nearly 

 entirely black, or with scattered dark spots ; chin and subcaudaF 

 siu-faces not sharply differentiated from dark color of belly 10> 



10. Belly almost completely black (or perhaps a midventral black sti'ipe) ; 



lateral light stripe not restricted to third row anteriorly — angustirostris- 

 BeUy not with a median, more or less extensive black stripe ; lateral 

 stripe restricted to third row or not 11 



11. Lateral stripe, when evident, restricted to third row anteriorly 12 



Lateral stripe always well defined, on second and third rows 13 



12. Vertebral light stripe one and two half scale rows wide, at least at 



base of tail marciana 



Vertebral light stripe one scale row wide, or nearly indistinguishable, 

 even at base of tail ruthveni 



13. No dorsal stripe ; scale rows at middle of body usually 21 hammondii 



A dorsal stripe; scale rows at middle of body generally 19 (an ante- 

 rior pair usually dropping before reaching midbody) ordinoides hueyi 



14. Preoculars two or more, rarely one ; belly usually with a continuous, 



longitudinal black area on center; scale rows 19 on anterior third 



of body 15 



Preoculars single; belly not with a continuous black area (or if so, 

 scale rows no more than 17) 1& 



15. Black on belly and tail very extensive, covering nearly all of ventral sur- 



face ; vertebral and lateral light stripes evident in all except large 

 specimens; second labial generally (81 percent) in contact with ros- 

 tral; postoculars usually (75 percent) 3-3 or more; caudals usually 

 64 or less (84 percent) in males, 54 or less (73 percent) in 



females mielanog'aster melanogaster 



Black on belly and tail entirely absent or restricted to a midventral 

 line or a few scattered spots ; rarely light lines evident, never the mid- 

 dorsal ; second labial usually not (78 percent) in contact with i-ostral ; 

 postoculars usually (72 percent) 2-2 or 2-3; caudals usually over 64 

 (69 percent) in males, 55 (84 percent) in fenJales- melanogaster canescens 



16. Maximum dorsal scale rows 17, and no evidence whatever of a middorsal 



stripe on any part of body chrysocephalus 



Dorsal scale rows more than 17, or if only 17, a vertebral light stripe 

 present or indicated on some parts of body 17 



17. A pair of white or light parietal spots, bordered laterally by a moderately 



dark area in middle of each parietal, which is sometimes fused with 

 nuchal blotches, and is darker than most of remainder of dorsal 



surface of head (light) ; at least a black border about parietal spots 18 



No marks on center of parietals ; head nearly uniform light or dark above_ 19»^ 



18. Large spots present on body, usually a single series extending com- 



pletely across back phenax phenas: 



Spots on body (except on neck) poorly defined or absent— phenax halophilus 



