2 34 CHARACTERS OF VERTEBRATE ANIMALS 



serve the purpose of conducting poison from a poison-gland into 

 wounds made by the teeth, and it has been asserted that this is 

 the case in some members of this group. 



3. Cobras and Coral-Snakes are tropical forms in which the 

 front upper teeth are grooved poison-fangs, conducting venom 

 from poison-glands. Cobras are found in South Asia and Africa. 

 Examples are the Common Cobra of India {Naia tripudians), 

 called " cobra de capello " (hooded snake) by the Portuguese 

 settlers on account of its power, characteristic of the genus, of 

 inflating the skin of the neck when irritated. 



The Coral-Snake {Elaps corallinus) of South America and 

 the West Indies is a small form, in which the body is beautifully- 

 marked by broad scarlet rings alternating with much narrower 

 black rings with greenish edges. 



4. Sea-Snakes are venomous forms ranging from the Persian 

 Gulf eastwards as far as New Guinea and North Australia, 

 Their poison-fangs are of the same kind as described for cobras, 

 &c., and the hinder part of the body is flattened from side to 

 side so as to constitute a powerful swimming organ. Unlike land 

 snakes they cast their skins in pieces, and not in a continuous- 

 slough. 



5. Vipers of all snakes are the most specialized as regards 

 the mechanism of the poison-fangs. Of these, two are present, 

 and they are the only teeth in the upper jaw. The groove 

 seen on the front of the fangs of other poisonous forms is here 

 converted into a canal, open above to receive the fluid from 

 the large poison-gland, and below so that this may be intro- 

 duced into the wound. Hook-like teeth of the ordinary solid 

 kind are present on the roof of the mouth and along the- 

 margin of the lower jaw. The head of a viper is flat and 

 triangular, possessing more • than in any other kind of poisonous 

 snake the shape of the conventional " spade " on a playing-card, 

 which is so often quoted as characteristic of venomous species. 

 It is, however, a fallacy to suppose that all the dangerous reptiles- 

 of the order can be easily distinguished in this way. 



Two species may be taken as examples, the Adder (Pelias 

 berus) (fig. 146) and the Common Rattle-Snake {Crotalus durissi- 

 mus). The former is the only poisonous British snake, and it has- 

 a very wide distribution in both Europe and Asia. Smaller than 

 the Grass Snake, it may be distinguished from that species not 



