SNAKES OF CEYLON. 3 



TAIL ROUND IN SECTION. Families. 



(B) Ventrals enlarged, but not twice last costal 



row (see fig. 11 ). Anal divided into two ; 

 twice breadth of ventrals (see fig. 11). 

 Costals broader than long. 



(a) Supralabials four . . . . Uropeltidse 



(6) Supralabials six .. .. Ilysiidse 



(C) Ventrals 2 to 2\ times breadth of last costal 



row (see fig. 17). Anal as broad as ven- 

 trals (see fig. 17). 



Costals broader than long. Eye mobile, 

 surrounded by many shields. 



Pupil vertical. 



(a) Costals in 15 rows at midbody . . *Xenopeltida3 



(b) Costals more than 40 rows at mid- 



body . . . . Boidsfi 



(D ) Ventrals more than three times as broad as 



last costal row. Anal as broad as ven- 

 trals. Costals as long or longer than 

 broad. Eye mobile, surrounded by- 

 many shields. 



(a) No mental groove. Three pairs of 



large asymmetrical sublinguals. 

 Pupil vertical . . . . *Amblycephalidse 



(b) A mental groove. Two pairs of sub- 



linguals (see fig. 20). Pupil variable 



(except Chersydrus-f) .. Colubridse (ex- 



cept Hydro- 

 phiinse) 



(c) A mental groove. One pair of sub- 



linguals (see fig. 91 ). Pupil variable Viperidse 



TAIL COMPRESSED INTO A FIN . . Sub-family Hy- 



drophiinse of 

 Colubridse 

 For Ceylon Species. 

 Ventrals not enlarged . . Typhlopidse 



Ventrals enlarged : — 



Last costal row f breadth of ventrals. Anal 

 twice or nearly twice breadth of ventrals : — 



Eye in a single shield . . Uropeltida? 



Eye surrounded by shields . . Ilysiidse 



Last costal row ^ breadth of ventrals. Anal 



as broad as ventrals . . . . Boidse 



Last costal row one-third or less the breadth of 

 the ventrals. Anal as broad as ventrals : — 



Two pairs of sublinguals . . Colubridse 



One pair of sublinguals . . Viperidse 



* Not represented in Ceylon. 



t Chersydrus has no ventral shields developed, its costals broader 

 than long, no mental groove, and no sublinguals. 



