CHAPTER IV. 

 GEOGRAPHICAL DISTRIBUTION OF VENOMOUS SNAKES. 



New Zealand is entirely free from snakes. Australia and its adjacent islands 

 are free from the Viperidae containing neither the Viperinae nor the Crotal- 

 inae. The American continents are noted for the absence of the true viperine 

 forms, whereas the Crotalinae, another representative of the Viperidae family, 

 is fully established throughout temperate and tropical America. The famous 

 rattlesnakes are the most specialized of all the venomous snakes and are 

 exclusively confined to the New World. The total absence of the poisonous 

 Colubridae from Europe is another remarkable geographical feature, and it 

 is highly interesting to note that the only venomous snakes here belong to 

 the Viperinae, of which but one genus is represented. In Africa the repre- 

 sentatives of the Viperinae are most numerous, but there are none of the 

 Crotalinae; of the Colubridae no Hydrophiinae are found, while the Elapinae 

 are fairly numerous. 



Asia contains almost every genus of poisonous serpents, except Crotalus. 

 The Elapinae are well represented by Naja, Bungarus, Hemibungarus, Cal- 

 lophis, and Doliophis, while the Hydrophiinae are most abundant along the 

 coasts of the tropical regions of Asia. The true vipers are not unknown 

 here, as the Viperinae are represented by four genera. The crotalines are 

 abundantly represented in Asia, as far as its western neighboring continent 

 Africa, both by Ancistrodon and by Lachesis, better known as Trimeresurus, 

 but, as was stated above, no Crotalus or rattlesnake. Thus Asia may be 

 looked upon as a region where the evolutional balance of various venomous 

 snakes is comparatively well preserved. 



One of the most extraordinary facts is that Australia is an exclusive home 

 of venomous Colubridae, of which no less than 16 elapine and 9 marine 

 genera are enumerated; but, as pointed out previously, there is no representa- 

 tive here of the Viperidae. 



Returning to the American continents, the conditions are found to be quite 

 contrary. Here peculiar relations exist between the Crotalinae and the 

 Colubridae both Elapinae and Hydrophiinae on one hand, and Crotalinae 

 and Viperinae on the other. The prevailing venomous snakes of America 

 belong chiefly to Crotalinae, and the colubrine and the viperine snakes are 

 thrown into the background. Especially no true vipers exist on this continent. 

 Of the colubrine snakes only one genus is represented, Elaps, 1 which, although 

 it includes more than 20 species, is in a state of more or less general degra- 

 dation, as may be judged from its diminutive size and its tendency to burrow. 



1 Another genus was described, Micropechis, with only one species, elapoides. 



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