B. Nostrils lateral. 



I. Teeth very small, equal, closely set, 37 — 50 in 

 each maxillary, head not or slightly distinct from 



neck; pupil round; scales smooth, in 17 rows. 9. Polyodontophis p. 54, 

 II. Maxillary with less than 40 teeth. 



t Head distinct from neck; internasals distinct 

 from praefrontals. 



1. Pupil round. 



a. Scales oblique, at least anteriorly. 



X Scales in 19 rows 10. Pseudoxenodon p. 56. 



XX Scales in 13 — 15 rows. 



aa. Maxillary teeth 20 — 33, posterior 



enlarged II. De?jdrophis p. 57. 



3iJ. Maxillary teeth 18 — 23, anterior 



longest 12. Dcndrelaphis p. 67. 



b. Scales in longitudinal series. 



1. Scales in even numbers, 12, 16 or 18. 13. Zaocys p. 71. 



2. Scales in odd numbers. 



+ Posterior maxillary teeth longest. 

 <7a. Maxillary teeth 18 — 40, conti- 

 nuous; scales keeled, in 15 — 21 



row^ 14. Tropidonotus p. 73. 



bb. Maxillary teeth 14 — 22, last two 



very large, separated from the 



others; scales keeled, in 19 rows. 15. Macropisthodon p. 91. 

 cf. Maxillary teeth 25 — 30; scales 



smooth, in 17 rows 16. Xenelaphis p. 93. 



dd. Maxillary teeth 12 — 20; scales 



smooth or keeled, in 13, 15 or 



17 rows 17. Zamenis p. 95. 



-|-+ Maxillary teeth equal. 



a. Ventrals rounded or angulate late- 

 rally; scales in 19 — 27 rows. . . 18. Coluber p. 98. 



b. Ventrals and subcaudals with a 

 lateral keel and a notch on each 



side; scales in 19 rows 19. Gonyophis p. 106. 



2. Pupil vertically elliptic. 



a. Anterior maxillary teeth enlarged, sepa- 

 rated from the rest. 



1. Body long; scales smooth or keeled, 



in 17 — 21 rows 20, Lycodon p. 107. 



2. Body extremely slender; scales keeled, 



in 17 rows 21. Lepturophis p. 113. 



