378 
COMPARATIVE ZOOLOGY. 
Being less under the influence of Man, they have not been 
forced from their original habitats. None are arctic. 
America is the most favored spot for Frogs and Salaman¬ 
ders, and India for Snakes. Australia has no Batrachians, 
and two thirds of its Snakes are venomous. In the United 
Fig. 361.—Zones of Animal Life. 
States, only twenty-two out of one hundred and seventy- 
six are venomous. Frogs, Snakes, and Lizards occur at 
elevations of over fifteen thousand feet. Crocodiles, and 
most Lizards and Turtles, are tropical. 
Swimming Birds, which constitute about one fourteenth 
of the entire class, form one half of the whole number in 
