ANIMALS OF THE PAST 



343 



Animals of the Paleozoic: Era 



Now we find ourselves 

 on very much surer 

 ground. At the usher- 

 ing 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 amphijjians, 

 and a few primitive rep- 

 tiles came in. So, after 

 all, the verteljrate ani- 

 mals appeared rather 

 early in the geological 

 history of the earth. 



Trilobites. — The most 

 important animals of the 

 earty paleozoic were the ti'ilobites 



Gruup of cup corala 



Fig. 217.— Trilobite. 



members of the branch, 

 Arthropoda. The bod- 

 ies of these animals were 

 di^dded into three longi- 

 tudinal loljes, separated 

 by t^^^o furrows, some- 

 times deep and some- 

 times .'^hallow and 

 ojxscure (Fig. 217). The 

 trilobites p.^issessed nu- 

 merous jointed append- 



