174 THE GEOLOGICAL SUCCESSION 



represented at present by the star fishes and sea-urchins, a 

 far more highly organized race. Numerous brachiopod 

 molluscs, the lowest of the class, have been discovered in 

 the Paleozoic rocks. The class of worms is represented by 

 a few serpulse. But the most convincing proof of the 

 organic inferiority of the first animal inhabitants of our 

 globe is afforded by the remains of the fossil vertebrata of 

 this epoch which are those of a low order of fishes. These 

 were then the most highly organized animals. Hence the 

 period has been called by Agassiz, the Age or Fishes. 

 There was as yet neither reptiles, birds, nor mammals. 

 The sea appears to have covered the greater portion of the 

 earth — an ocean without a shore. The animals were all 

 aquatic, and the vegetation marine; and "among the aqua- 

 tic population no sound was heard. All creation was then 

 silent."* 



Towards the close of the paleozoic period, the earth ap- 

 pears to have presented the aspect of a vast ocean studded 

 with an immense number of islands, which were covered 

 with a luxuriant vegetation, consisting principally of arbor- 

 escent ferns, Equisetaceae, Calamites, Lycopodiaceae, and 

 Coniferse — ^plants of very simple structure, but of gigantic 

 size. It was during this geological era that the coal was 

 deposited. 



The animals of the carboniferous formation resemble, in 

 many respects, those of the paleozoic epoch. The crus- 

 taceans, however, have evidently improved. In addition 

 to the trilobites, we have the horse-shoe crabs, and other 

 gigantic forms. We also meet with trao6s of insects and 

 scorpions. We come now to that immense period in the 

 natural history of the earth, which geologists have called 



The Secondary Age, or the Age oe Reptiles. The 



^ Loais Agassiz. 



