6 THE POISONOUS SNAKES OF INDIA. 



A glance at this simple key will enable the enquirer to isolate two 

 large groups of harmless snakes, by an inspection of the belly shields 

 alone, and a third group of poisonous snakes by the conformation of 

 the tail (sea snakes). 



It is a somewhat diflScult matter to decide where to draw the line 

 between the so-called non-poisonous and the poisonous varieties. To 

 begin with, all the viperine snakes are poisonous, and from investigations 

 conducted by Alcock and Kogers* in Calcutta in 1902 it appears 

 probable that all colubrme snakes contain in their saliva a toxic element 

 identical with that to which the poisons of the cobras, kraits, and other 

 deadly colubrines owe their lethal properties. If this is so, strictly 

 speaking, all colubrines are poisonous, and their various salivas merely 

 differ in degrees of toxicity. 



The Colubridce are divided into three groups : (1) Aglyplia 

 characterised by the absence of a poison fang, (2) Opisthoghjpha, snakes 

 furnished with a specialised tooth in the form of a grooved fang situated 

 at the back of the maxilla (upper jaw bone), and (3) Proteroglypha, 

 snakes endowed with a specialised grooved tooth (fang) in the front of 

 the maxilla. It is to the third group that I reserve the term " poison- 

 ous," purely as a term of convenience however, for although all the 

 snakes whose bite is known to prove fatal to man fall into this category 

 many of the group are known to produce baneful effects usually 

 falling short of death, whilst -the effects of many others remain in 

 obscurity. 



The difficulty in laying down hard and fast rules by which 

 to distinguish the poisonous varieties and separate them one and 

 all from their non-poisonous allies may be appreciated from the 

 fact that there are no less than o20 species already known within 

 our limits, of which 68 are poisonous. Of these 68 species, 39 are 

 terrestrial, 29 marine. All the poisonous species fall into one of 

 the following 5 groups with one solitary exception, viz., Azemiops 

 fecE^ the existence of which may be ignored for all practical pur- 

 poses since only one specimen is known. It was found in the 

 Kachin Hills, Burma. 



* Proceedings of the Royal Society, 1902, p. 446 



