70 EXTINCT ANIMALS. 



depending largely upon the imagination and ingenuity of 

 the reader. 



Lastly, we may note that there are important animal 

 types which have their origin, and their end, within the 

 geological record. These are called extinct animals and their 

 study forms one of the most interesting chapters in zoology.'^ 

 Orders and classes which now are represented by a small 

 remnant aj pear to have flourished in the past in an 

 astonishing manner until they were replaced by other types. 

 The proximaie agent causing their extinction may in many 

 cases be obscure, but it is evidently part of a general law 

 which ensures that the phylum, the class, the order, the 

 genus, and the species shall arise, flourish, and depart in 

 the same way as the individual. 



* The study of extinct animals is often termed Palaeontology, but it 

 is inseparable from Zoology. 



