256 BRANCH CHORDATA 



of these being the " salt-water crocodile " of the Malay Peninsula. The 

 American crocodile and the alligator are not dangerous to man. 



" The Florida crocodile is the only crocodile which inhabits a country 

 that is visited by killing frosts."' It is most abundant in low wet lands and 

 shallow water, where the mainland sinks into the gulf. There is a Cuban 

 crocodile and two South American species. 



Distribution of Reptiles. — The animals of this class are 

 generally tropical and subtropical. Snakes are said to extend 

 farther north in America than do lizards. In Europe snakes are 

 not found north of 60°, while lizards are sometimes found farther 

 north or at an elevation of ten thousand feet. 



Lizards are the most numerous of reptiles at the present time, 

 and are found in all except the circumpolar regions. 



Chelonia are also widely distributed in the tropical and tem- 

 perate regions. 



The alligators occur only in North America and in China, and 

 the Caimans are found only in Central and South America. 

 Crocodiles are distributed over Africa, southern Asia, northern 

 Australia, and tropical America, there being one species in 

 Florida. 



True reptiles are known to have existed in the Permian Pe- 

 riod. Indeed, there was such a "variegated reptilian fauna" that 

 it is believed their ancestors must have lived in the Carboniferous 

 Period. One of the Permian orders ( Theromor'pha) exhibits cer- 

 tain strong points of resemblance to the earliest amphibians and 

 other jDoints of resemblance to the lower animals. They have 

 been found in rocks of the Permian and Triassic Periods, but in 

 none of the more recent formations. These fossils have been 

 found in Texas, South America, Europe, Africa, and India. 



Lizard-like forms {Sauroptery' gia) existed in the Cretaceous 

 and Triassic and possibly in the Permian periods. They varied 

 from small forms up to those of 40 feet in length. A fish-like 

 form (Ichthyoptery'gia), varying from 30 to 40 feet in length, ex- 

 isted from the upper Triassic to the upper Cretaceous periods. 

 In the Triassic were also forms allied to the crocodile. 



One of the most characteristic of the Mesozoic orders of 

 reptiles was the Dinosauria, many of which existed in the Triassic 

 Period. Some were herbivorous, others carnivorous. Some 



1 Hornaday. 



