GEOGRAPHICAL DISTRIBUTION OF VENOMOUS SNAKES 



53 



The predominance of the crotaline snakes is most remarkable. While the 

 genus Ancistrodon is less numerously represented than in Asia, Lachesis is 

 much more in evidence. Moreover, two new genera have made their appear- 

 ance on the American continent, namely, Crotalus and Sistrurus. Both are 

 characterized by the presence of the "rattles" at the end of the tail. 



Of 8 different genera, 4 (Vipera, Echis, Pseudocerastes, and Cerastes) are 

 found in Asia and Africa in common, and Vipera also in Europe, but the rest 

 are characteristic of each continent. It does not follow, however, that these 

 same genera occurring in different continents are represented by the same 

 species. On the contrary, the species of a genus vary according to the prosper- 

 ity enjoyed by the genus on the particular continent. The members of the 

 genus Vipera have different species-characteristics, depending upon whether 

 they inhabit Africa, Asia, or Europe. Of 4 genera of the subfamily Crotalinae, 

 Ancistrodon and Lachesis inhabit both Asia and America, but the constituent 

 species of these two genera differ widely according to the continent to which 

 they belong. It is also seen that of 28 genera of the subfamily Elapins, only 

 the Naja is met both in Africa and in Asia, and of that genus there is no 

 species common to both continents. 



It is noteworthy that even the marine snakes, whose pelagic nature would 

 render almost any artificial geographical boundaries of ocean insignificant, 

 seem to have more or less restricted habitats. Thus, some genera prefer to 

 swim about the coasts of tropical Asia, and especially along the Indian and 

 Malayan coasts and Archipelago, while still others seem to be confined near 

 Sydney. In general, however, the habitat of the marine snakes is highly 

 uncertain and reports of the capture of certain species from unexpected 

 parts of the globe add difficulties to this particular point. 



EUROPE 



Viperinae- 



1 genus, S'speicieiS^^ 



Viperinae-' 

 7 genera, 32 species 



Eiapinae- 

 7 genera, 21 species 



ASIA 



;;yiperinae 



4 genera, 8 species 



Crotalinae^ 



2 genera, 24 species 



-Eiapinae 

 5 gen 



Hydroplii 

 10 ger 



AMERICA 



* Comprises only Ancistrodon, and Lachesis, but no " rattlesnakes. 

 ** Comprises Ancistrodon, Lachesis, Sistrurus and Crotalus. 

 *** 27 species out of this ntxmber belong to genus Elaps. 



'Crotalinae' 

 4 genera, 43 species 



'Eiapinae ^ ^^^ 



2 genera, 28 species 



Eiapinae 



15 genera, 61 species 



Hydrophinae 



9 genera, 10 species 



