THE POISONOUS SNAKES OF INDIA. 39 



GROUP 4.— THE PIT-VIPERS. 



Identification. — (1) Tail round. (2) A conspicuous opening in 

 the side of the face between the eye and the nostril (the loreal pit) (see 

 Fig. 24 B). 



This very distinctive character is peculiar to this sub-family of 

 vipers. In spite of the fact that many members of this sub-family 

 (Crotalinee) attain formidable proportions, and almost all are 

 endowed with remarkably large poison fangs, the numerous accounts 

 of bites inflicted by them to be found in scientific and other jour- 

 nals concur in showing that death is an exceedingly rare event. 

 My own experience, supported by that of many of my friends, who 

 have favoured me with letters on this subject, entirely confirms the 

 foregoing. A painful and swollen condition locally and a very 

 variable degree of constitutional disturbance lasting in some in- 

 stances for weeks passes on to complete recovery. 



These snakes are nearly all exclusively confined to hilly regions 

 at altitudes ranging between 1,500 to 10,000 feet. The characters 

 of the shields, and scales upon which the classification of nearly allied 

 ophidian forms is so largely based, are subject to very great incon- 

 stancy in the members of this group, so much so that it is with the 

 greatest difiiculty one can frame a lucid and really practical key to 

 identify the various species. I have, however, examined and re- 

 examined most critically all the specimens in the British Museum, 

 and have only made allusion to those peculiarities which are most 

 constant, and which seem to me of real practical use in identification. 



Key for identification of Pit-Vipers, 



HEAD WITH LARGE SHIELDS {see Figs. 24 to 27). 



Scales midbody in 21 or 23 rows (see Fig. 7) . .Ancistrodon himalayanus. 



Scales midbody in 17 rows 



(a) Supraocular as broad as frontal, longer than 



parietals , . . Ancistrodon hypnale. 



(J) Supraocular broader than frontal, shorter 



than parietals ,_ millardi. 



Scales midbody in 15 or 14 rows Lachesis macrolepis. 



