222 



VIPERID.E 



very small, usually smaller than the nasal shield, its 

 horizontal diameter usually not exceeding its distance 

 from the posterior border of the nostril, its vertical 

 diameter often less than and rarely exceeding its 

 distance from the mouth. Length of tail seven to 

 eight times in total length in males, nine and a half 

 to twelve times in females. 



Head-Shields. — Rostral as deep as broad or slightly 

 deeper than broad, visible from above, in contact 



with one 

 apical shield 

 (rarely with 

 two). Dis- 

 tinct frontal 

 and (usually) 

 p a r i e t a 1 

 shields, the 

 former once 



Fig. 33 (From Proceedings of the Zoological and a half 

 Society, 1893) , 



to once and 

 two-thirds (rarely once and one-third) as long as 

 broad, as long as its distance from the rostral 

 or the end of the snout, and nearly always longer 

 than the parietals ; the latter always in contact 

 with the former, rarely broken up into small 

 shields. Four to seven small shields on the snout 

 between the canthals, of which there are two on 

 each side. Supraocular well developed, extending 

 posteriorly beyond the vertical of the eye, separated 



