A?ilmals Before Man 



brates, because their form is believed to have 

 changed with their mode of life, and they have 

 not merely failed to progress, but have actually 

 gone backward, and lost the position occupied 

 by their remote ancestors. 



Owing to their soft texture these animals 

 have left few traces of their existence at for- 

 mer periods of the earth's history, although we 

 do find evidence of their presence in some Mio- 

 cene rocks. 



Such are the great, primary divisions or 

 classes of the great and important phylum or 

 subkingdom of back-boned animals, or verte- 

 brates, and these once fixed in the mind it is an 

 easy matter to refer to their proper places the 

 unfamiliar creatures with which we may have 

 to deal. 



Representatives of all the classes of verte- 

 brates are found fossil, and not only examples 

 of all existing orders, but of a number that 

 have become extinct. Fishes are perhaps the 

 most common of fossil vertebrates, ]3artly on 

 account of their numbers and partly because 

 they had a commendable habit of dying where 



40 



