THE REPTILES OF THE PACIFIC COAST AND 



GREAT BASIN. 



Introduction. 



The term reptile is popularly applied to all cold-blooded 

 vertebrates other than fishes. Thus used it includes two 

 groups of animals which differ in many important re- 

 spects. These are the batrachians and the reptiles 

 proper; the former more closely allied to the fishes; the 

 latter, to the birds. 



The typical batrachians, such as most frogs, toads, 

 salamanders, etc., lay their eggs in the water, and the 

 young, for a time, breathe by means of gills, very much 

 as do the fishes. Later on, they undergo a metamor- 

 phosis, during which the gills and other larval charac- 

 teristics disappear, the tadpole assumes the form and 

 structure of its parents and emerges from the water to 

 breathe air and spend a greater or less portion of its life 

 on land. The skin of batrachians* is not provided with 

 scales, but is smooth or warty, very glandular, and often 

 covered with a slimy secretion. 



The true reptiles, such as alligators, turtles, lizards, 

 and snakes, on the other hand, never lay their eggs in 

 the water, even the marine species coming to land for 

 this purpose. Their young never breathe by means of 

 gills, but are hatched or born with the form and struc- 

 ture of the adult. The skin, except of some turtles, is 

 covered with scales, and is dry, never slimy. 



There are, also, many anatomical and embryological 

 differences between the two classes, but these need not 



♦Except Coecillans of tropical lands. 



