CARNIVOROUS AND INSECTIVOROUS REPTILES 79 



The largest known snakes, Pythons and Boas (see vol. i, 

 p. 231), as well as many smaller kinds, adopt a much more 

 merciful procedure than the Grass Snake, for they kill their prey 

 by crushing it in their coils before beginning to swallow it, the 

 latter proceeding being greatly facilitated by the secretion of large 

 quantities of saliva. The largest of all such species is the gigantic 

 Anaconda (Euneces murinus}, inhabiting the tropical forest regions 

 of South America, where it haunts the rivers and their neighbour- 

 hood, often hanging head downwards from a tree on the look-out 

 for prey. Many such reptiles are thoroughly arboreal in habit, 

 as for instance the Tree -Boas of tropical regions, though their 

 climbing powers do not preclude expertness in swimming. 



A certain number of snakes are adapted for pursuing such 

 prey as can be found underground, more especially earth-worms. 

 The most important are the Shield-tailed Snakes (Uropeltidcz) 

 of India and Ceylon, and the widely-distributed Blind- Snakes 

 (Typhlopidce), found for the most part in tropical regions. They 

 are never of large size, and their smooth scales present but little 

 resistance to passage through the earth, while, as so often happens 

 in creatures which lead an underground life, the eyes are much 

 reduced, and in this case are protected by special shields. The 

 nature of the food does not demand those expansive powers 

 which are so characteristic of average snakes, and the mouth is 

 consequently small and incapable of being stretched to any extent. 



Poisonous Snakes. We now pass to the consideration of 

 poisonous forms, which are distinguished by the grooved or 

 tubular nature of some of the teeth attached to the margin of 

 the upper jaw, the object of this being to conduct poison into any 

 wound which may be inflicted. Such modified teeth may be 

 situated either at the front or back, and though their presence 

 may be taken to indicate a greater or less degree of poisonous 

 properties, it by no means follows that all such forms are dan- 

 gerous to man. The slender Whip- Snakes (Dryiophidcz) of India 

 and the Malay region are among the forms where the poison-fangs 

 are formed by modification of the hinder teeth. They are arboreal 

 in habit, climbing among trees with great rapidity, and preying 

 upon small vertebrates, such as birds and lizards. Well-known 

 examples of venomous serpents, in which the poison-fangs are at 

 the front end of the upper jaw, are the brilliantly-coloured Coral- 

 Snake (Elaps] of South Africa and the hotter parts of America, 



