280 COLUBEID^E. 



c". Eye rather small, moderate or 



large, with round pupil. 

 a. Maxillary teeth few ( 6 to 12), 

 very strongly enlarged pos- 

 teriorly ; eye rather small ; 

 rostral shield large. 



a'. Pterygoids toothed SIMOTES, p. 300. 



j3'. Pterygoids toothless OLIGOPON, p. 317. 



/3. 12 or more teeth in each max- 

 illary, increasing in size pos- 

 teriorly. 



a'. Body moderate, not com- 

 pressed ; no subocular ; eye 



rather small COHOXKLLA, p. 308. 



/3'. Body slender ; a subocular 

 below the praeocular ; longi- 

 tudinal rows of scales in odd 



numbers ZAJJENIS, p. 323. 



y. Body slender ; longitudinal 

 rows of scales in even 



numbers ' ZAOCYS, p. 329. 



y. 15 or more teeth in each max- 

 illary, subequal in length. 

 a'. 40 to 50 teeth in each max- 

 illary ; scales in 17 rows . . POLYODONTOPHIS, p. 301. 

 /3'. 15 to 30 teeth in each max- 

 illary. 



a". Scales in 15 to 19 rows, 

 without apical pits, verte- 



brals not enlarged ABLABES, p. 304. 



/3". Scales in 19 to 27 rows, 

 with apical pits, verte- 



brals not enlarged COLUBEH, p. 330. 



y' 1 . Scales in 17 rows, without 

 apical pits, .of vertebral 



row enlarged XENELAPHIS, p. 33G. 



b. Posterior border of ventral shields with 



a notch on each side corresponding to 



a suture-like lateral keel ; scales in 



13 or 15 rows. 



a'. Maxillary teeth equal in length ; 



scales of vertebral row enlarged . . DENDROPHIS, p. 337. 

 V. Anterior maxillary teeth longest; 



vertebral scales not enlarged .... DENDBEL APHIS, p. 339. 

 B. Aquatic or seniiaquatic Snakes, with the 

 hypapophyses developed throughout the 

 vertebral column, and very small nasal 

 bones. Scales usually keeled. 

 a. Posterior maxillary teeth longest. 

 '. Scales on the anterior part of the 

 body disposed obliquely, narrow 



and much imbricate PSEUDOXEXODON, p. 340. 



//. Scales forming straight longitudinal 



series ; two interuasals TROPIDOXOTUS, p. 341 . 



