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 Crotaline, 
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 Elapine, 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 

AMERICA 



Crotalinae** 
4 genera, 43 species 


AFRICA 



Elapinae | RR 
2 genera, 28 species 


Viperinae 
7 genera, 32 species 







Elapinae 
AUSTRALIA 
7 genera, 21 species 


Elapinae 
15 genera, 61 species 
* Comprises only Ancistrodon, and Lachesis, but no “ rattlesnakes.” 
** Comprises Ancistrodon, Lachesis, Sistrurus and Crotalus. 
*#* 27 species out of this number belong to genus Elaps. 
Hydrophinae 
9 genera, 10 specles 
