234 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 

 Gull 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 



