﻿250 VIPERID^ 



Form. — Short and heavy. Snout pointed, pro- 

 duced into an erect, horn-like dermal appendage 

 covered with scales ; canthus rostralis strong, some- 

 times slightly raised, loreal region slanting more or 

 less towards the lip. Vertical diameter of the eye 

 less than its distance from the mouth in the adult. 

 Length of tail six to nine and a half times in the total 

 length in males, eight to eleven times in females. 



Head - Shields. — Rostral usually broader than 

 deep. Naso-rostral (rarely divided into two) usually 



reaching the 

 canthus rostra- 

 lis, and extend- 

 ing considerably 



higher up than 



the upper border 

 of the rostral. 

 Rostral append- 

 age covered with 



Fig. 38 (after Sordelli) , 



^ ^ ten to seventeen 



scales, arranged in three (rarely two or four) trans- 

 verse series between the rostral shield and the apex. 

 Upper surface of head covered with small smooth or 

 faintly keeled, subimbricate scales, among which a 

 feebly enlarged frontal shield or a frontal and a pair 

 of parietals are rarely distinguishable ; when present, 

 the frontal is separated from the supraocular by two 

 series of scales ; on the vertex five to eight series of 

 scales separate the supraoculars. Two (rarely three) 



