28 THE POISONOUS SNAKES OF INDIA. 



Nicholson's footnote on page 159 of his work on Indian snakes is a 

 striking corroboration of my own experience. He says : " I have 

 " seen an Englishman, considered rather an authority on snakes, 

 " declared that a Ptyas mucosus (now Zwmenis mucosus) just brought 

 " to me was a cobra ; he even pointed out the poison-fangs.^' So 

 long as people continue to be guided by these faulty characters in 

 diagnosis, mistakes are sure to occur. 



Now there are one or two very distinctive peculiarities about 

 the scales of a cobra which if looked for should place its identity 

 beyond question. These are as follows :— 



The prceocular shield touches the internasal* (See Pra. and Int., fig, 

 16 B). In only two other snakes is this relationship to be found, 

 vh., in Xylophis perroteti, a small harmless snake peculiar to the 

 hills of Southern India, and the rare Amhlycephalus monticola. In 

 both the third supralabial shield does not touch the nasal. 



Between the Mh and 5th infralabial shield a small wedge-shaped 

 scale occurs, the " cuneate " {see fig. 16 B). Sometimes a second 

 or even a third similar scale borders the lower lip. This scale may 

 easily be overlooked, lying partly or wholly concealed, as it may do, 

 by the overlapping of the upper lip, so that the mouth should be 

 opened when looking for it. It occurs in no other land snake. I 

 have never even observed it in the hamadryad, but it is seen in a 

 few species of sea-snakes. A head is rarely so broken that one or 

 other of these points cannot be made out on one side. If, how- 

 ever, the head is mutilated beyond recognition there is one feature 

 about the scales over the back of a cobra which is peculiar to itself. 

 It is the concavity in the arms of the bracket-shaped pattern 

 which these form, and which I have shown by thickened lines in 

 fig. 17. Beside this, I have placed another drawing to illustrate 

 what is seen in other snakes, the pattern forming a chevron. This 



* This is a very easy point to determine if it is remembered that the shields 

 immediately behind the rostral (in land colubrines) are called internasals, and the 

 shields touching the front of eye the prseoculars. In the instances where the prse- 

 f rental shield touches the eye as in Fipr. 19, it is obvious that this shield from its 

 size and position has a prior claim to be considered a prsefrontal, and in such a case 

 the prseocular is said to be absent. 



