THE POISONOUS SNAKES OP 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 confor- 

 mation of the tail (sea snakes). 



It is a somewhat difficult 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 in- 

 vestigations conducted by Alcock and Rogers* in Calcutta in 1902, 

 it appears probable that all colubrine 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 Golubridw are divided into three groups : (1) Aglypha 

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

 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) 

 Proterogh/pha, 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 "poisonous," 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 330 species already known within our 

 limits, of which 69 are poisonous. Of these 69 species, 40 are 

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

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

 fern, 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. 



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



