26 COLUBRID. 
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 differentiation. 
Synopsis of the Species. 
I. Rostral 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. Seales in 15 to 19 rows. 
a. Anal entire. 
Scalesun 15 rows, smooth. 30.50 soe as 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. 
SAUGIMVMICBELOC. «. 4: st juis casein te.S toraseusiste. 2 3. nove-hispania, 
b. Anal divided. 
penles in 17 rows, keeled ...s.i<-5-<i5 4. melanotropis, p. 33. 
Scales in. 19 rows, smooth........:..... 5. porphyraceus, p.d4. 
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. helena, p. 36. 
b. Anal usually divided. 
a. Scales smooth or faintly keeled. 
* Rostral as broad as deep. 
Scales in 23 rows; subcaudals 79-90 .... 7. hodgsonit, 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, division B of this 
key. 
