6 INTRODUCTION 



Sub-class I. Stegocephali 



Extinct amphibians with well-developed tail; the skull without 

 gaps, except for eyes and nostrils, in the dorsal surface. 



Sub-class II. Urodela 



Amphibia with well-developed tail, gills sometimes retained 

 through life. — Salamanders, Tritons, newts, efts. 



Sub-class III. Anura 



Tailless as adults, the young a tadpole with external gills. — Frogs 

 and toads. 



Sub-class IV. Gymnophiona 



Blind, burrowing, legless amphibians occurring in the tropics. — 

 Caecilians. 



Grade II. Amniota 



Vertebrates in which there are never fins, never functional gills, 

 the respiration being by lungs. In development the embryo becomes 

 covered by an embryonic envelope called the amnion, while a second 

 outgrowth from the hinder end of the digestive tract is concerned in 

 the embryonic respiration and nutrition and is called the allantois. 



Class I. Sauropsida 



Body, at least in part, with scales, eggs large, lower jaw sus- 

 pended from skull by a quadrate bone. 



Sub-class I. Reptilia 



Cold-blooded vertebrates, the whole body covered by scales or 

 horny plates. The living forms are turtles, lizards, snakes and alli- 

 gators (crocodiles) and a New Zealand species, Sphenodon. The 

 fossil forms are more numerous and include Theromorphs, Plesio- 

 saurs, Ichthyosaurs, Dinosaurs, and Pterodactyls. 



Sub-class II. Aves 

 The birds are recognized by their warm blood and their feathers. 



