CONTENTS 



I 



PAGE 



Introductory. The form and movement of Fishes. Their classifica- 

 tion; geological distribution; mode of evolution. The survival of 

 generalized forms i 



II 



The Evolution of Structures characteristic of Fishes; e.g. (i) gills, 



(2) skin defences, teeth, (3) fins, and (4) sense organs .... 14 



III 



The Lampreys and their Allies. Their structures and probable relation- 

 ships. The Ostracoderms and Paloeospondylus 57 



IV 



The Sharks. Their plan of structure; prominent forms, living and 



extinct; their interrelationships 72 



V 



The Chimseroids. Their characteristic structures; their representatives 



and relationships 99 



VI 



The Lung-fishes. Their structures. Extinct and recent forms. The 



evolution of the group 116 



xi 



