ANIMALS OF THE PAST 



343 



Animals of the Paleozoic Era 



Now we find ourselves 



on very much surer 



ground. At the usher- 



mg in of this era the 



waters of the earth were 



teeming with myriads of 



animals, all invertebrates. 



Later in the era, for it 



was very long, the first of 



the fishes — an ancient 



type — some amphibians, 



and a few primitive rep- 

 tiles came in. So, after 



all, the vertebrate ani- 

 mals appeared rather 



early in the geological 



history of the earth. 

 Trilobites. — The most 



important animals of the 



early paleozoic were the trilobites, members of the branch, 



Arthropoda. The bod- 

 ies of these animals were 

 divided into three longi- 

 tudinal lobes, separated 

 by two furrows, some- 

 times deep and some- 

 times shallow and 

 obscure (Fig. 217). The 

 trilobites possessed nu- 

 FiG. 218.— Group of cup corals. merous jointed append- 



FiG. 217.— Trilobite. 



