IDENTIFICATION OF SNAKES. 



49 



ascertaining if certain species of snakes were immune to Puff Adder 

 venom, I allowed tiie adder to bite tliem, either in the neck or 

 somewhere in the region of the abdomen. In nearly all cases the 

 bitten snakes died a week or so later. However, I subsequently 

 discovered that tlie deaths were often caused not by the venom, 

 but by the actual mechanical injury caused to the internal parts 

 of the bitten snakes, by the large fangs of the Puff Adders. 



Identification of Snakes. 



In the identification of the species of snakes the colouration 

 is a most uncertain guide. The systematic Zoologist examines 

 the dentition to ascertain to what division the 

 specimen belongs. There are three main divisions, 

 viz. the AGLYPHA, or solid-toothed non-veno- 

 mous snakes ; the OPISTHOGLYPHA, or hind- 

 fanged, more or less poisonous snakes ; and the 

 PROTEROGLYPHA, or front-fanged, typically 

 venomous snakes. 



After finding out what family, sub-family, and 

 genus the specimen is a member of by means of 

 the general formation of the body, scales, and 

 shields, the zoologist identifies the species by 

 examining the shields on the head and abdomen. 

 The number and shape of the head and abdominal 

 shields differ in the various species of snakes. 

 Sometimes they merely shghtly differ in a species. 

 In these cases we term it a sub-species, if the 

 difference is observed to be constant. 



If you compare the head shields of two 

 different species of snakes, you will notice they 

 differ in shape. If the abdominal (ventral) shields 

 are counted they will differ in number. So also 

 will those from the vent to the end of the tail 

 (sub-caudals). In some species of snakes the shield 

 (anal) over the vent is divided. In others it is entire. So also with 

 the sub-caudals. In some snakes they are in one row, and in others 

 they are in two rows. Their number also differs with the species. 



Fig. 2 1.- — A. Ven- 

 trals or abdominal 

 shiclclii. They ex- 

 tend from throat 

 to vent. 



B. .^nal shield. In 

 some snakes this 

 shield, which 

 covers the vent, 

 is divided. In 

 others it is entire. 



C. Sub-caudal. 

 These shields in 

 some snakes are 

 in two rows ; in 

 others in a single 

 row. 



I 



