loo JOURNAL, BOJliiA Y NATURAL HISTORY SOCIETY, Vol. Xt V 



These may be distinguished by the former having the scales beneath 

 the tail (subcaudals) divided (as m fig. 12) and the latter undivided 

 (as in fig. 11). 



For the sake of completeness I have framed a key by which all the 

 poisonous may be separated from all the harmless varieties, but care 

 must be taken in employing this to take each point in the sequence 

 therein laid down, or wrong conclusions will be arrived at, and it must 

 be distinctly understood that this key will only hold good so far as 

 the snakes of India and the limits referred to above are concerned. 



A. Eye in a single shield (as in fig. 6.) Harmless. 



B. Eye surrounded by many shields (as in figs. 1, 



2,3, 4 and 7.) 



«'. Tails distinctly flattened 



a^. Head with large scales (see fig. 8.)... Poisonous, 

 Includes all the sea-snakes except one, 



29 varieties , 



V'^. Head with small scales {see fig. 9) ... Harmless. 

 The only exception to the rule that 

 sea-snakes are poisonous, viz., 



Chersydrus granulatus 



b^ . Tails round or nearly round 



a-. A pit jn face between eye and nostril 

 (as in fig. 7). Includes all the pit 

 vipers, " Crottalinse " 12 varieties. Poisonous. 

 b'-. No pit in face between eye and 



nostril. {See figs. 1, 2, etc.) 



a''\ No large scales on top of head 



(seefig.d) 



a^. Ventrals broad (as in fig. 11). 

 Includes the true vipers 



" Viperiucc'' 4 varieties Poisonous. 



b^, Ventrals, so narrow as to allow 

 a complete row or more of 

 scales to be seen on each side 

 simultaneously when snake laid 

 on back {see fig. 12). Includes 

 the sand-snakes Eiyx and 

 Gongylophis *. Harmless. 



