26 COIUBEID^. 



Maxillary teeth 12 to 22, subequal in size ; anterior mandibular 

 teeth longest. Head distinct from neck, elongate ; eye moderate or 

 rather large, with round pupil; loreal sometimes absent. Body 

 elongate, cylindrical or feebly compressed ; scales smooth or keeled, 

 with apical pits, in 15 to 35 rows ; ventrals rounded or angulate 

 laterally. Tail moderate or long ; subcaudals in two rows. 



Europe, Asia, North and Tropical America. 



The species comprised under this genus form a series nearly 

 parallel to that obtained in Zamenis, the extreme forms of both 

 these genera showing much the same amount of diiferentiation. 



Si/nopsis of the Species. 



I. Eostral shield not deeper than broad, the portion visible from 

 above not half as long as its distance from the frontal. 



A. Ventrals without or with a rather indistinct lateral keel *- 



1. Scales in 15 to 19 rows. 

 a. Anal entire. 



Scales in 15 rows, smooth 1. dichrous, p. 30. 



Scales in 17 rows, smooth or feebly keeled . 2. corais, p. 31. 

 Scales in 19 rows ; dorsals more or less dis- [p. 33. 



tinctly keeled 3. novoe-Msjpanice, 



h. Anal divided. 



Scales in 17 rows, keeled 4. melanotropis, p. 33. 



Scales in 19 rows, smooth 5. porphyraceus, p.34. 



2. Scales in 21 rows or more (rarely 19 in C cantoris), smooth 



or feebly keeled. 



a. Anal usually entire. 



Scales in 19 or 21 rows ; subcaudals 65-76. 6. cantoris, p. 35. 

 Scales in 23 to 27 rows ; subcaudals 75-94. 8. Tielena, p. 36. 



6. Anal usually divided. 



a. Scales smooth or faintly keeled. 



* Eostral as broad as deep. 



Scales in 23 rows ; subcaudals 79-90 .... 7. hodgsonii, p. 35. 

 Scales in 31 to 35 rows ; subcaudals 91-119. 9. triaspis, p. 37. 



* In some doubtful cases it will be necessary to try, also, diTision B of this 

 key. 



