GENERAL PRINCIPLES OF ZOOLOGY rf 



The Vertebrate Sub-Kingdom is divided into the 

 following five classes : — 



(1) Mammalia (mammals, animals which suckle their 

 young). 



(2) Aves (birds). 



(3) Eeptilia (reptiles, snakes, lizards, and turtles). 



(4) Amphibia (frogs, newts, and salamanders). 



(5) Pisces (fish). 



