280 COLUBEID^. 



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 SuroTKS, p. 300. 



/3'. Pterygoids toothless Otjoodon, p. 317. 



/3. 12 or more teeth in each max- 

 illary, increasing in size pos- 

 teriorly. 

 a. Body moderate, not com- 

 pressed ; no subocnlar ; eye 



rather small Coronella, p. 308. 



ft'. Body slender ; a subocular 

 below the prneocular ; longi- 

 tudinal rows of scales in odd 



numbers Zamexis, p. 323. 



y'. Body slender; longitudinal 

 rows of scales in even 



numbers Zaiioys, p. 329. 



y. lo or more teeth in each max- 

 illary, subequal in length. 

 «'. 40 to 00 teetli in each max- 

 illary ; scales in 17 rows . . Pota-opoxtophis, p. .301, 

 /3'. l-J to 30 teeth in each max- 

 illary. 

 «". Scales in lo to ID rows, 

 without apical pits, verte- 



brals not enlarged Vblahes. p. -304. 



(■i" . Scales in 19 to 27 rows, 

 with apical pits, verte- 

 bral? not enlarged Colubeb, p. 330. 



y'' . Scales in 17 rows, without 

 apical pits, of vertebral 



roAV enlarged Xknelapiiis, p. 330. 



//. 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 Dendrel aphis, p. 339. 



B. ^Vquatic or semiaquatic Snakes, with the 



hypapophyses developed throughout the » 

 vertebral column, and very small nasal 

 bones. Scales usually keeled. 

 a. Posterior maxillary teeth longest. 

 a . Scales on the anterior part of the 

 body disposed obliquely, narrow 



and much imbricate Pseudoxenodon, p. 340. 



//'. Scales forming straight longitudinal 



series; two internasals Tropidonotus, p. 341 . 



