CHAPTER XLVIII. 



THE PALCEOZOIC ERA. 



THE next period of the earth's history is called the Palceozoic 

 , or era of old life. This era includes the Silurian age, the 

 Devonian age, and the Carboniferous age. 



At the beginning of this era, besides the Lauren tian tableland, 

 there seems to have been a large body of land occupying the 

 region of the Atlantic coast plain ; and another in the region now 

 occupied by the Rocky Mountains. Between these bodies of land 

 there was a broad, shallow sea, called by some the Paloeozoic sea. 

 The earliest rocks of this era are sandstones and slates, composed 

 of materials that accumulated on the beach of this ancient sea, 

 over a region extending from Canada to Georgia. They are 

 known as the Cambrian rocks. In them we find the earliest re- 

 mains of life, representing protozoans, coelenterates,echinoderms, 

 worms, and crustaceans, nearly all the invertebrate forms of life, 

 besides several species of plants. 



This abundance of the various forms of life, calls attention to 

 the nature of the geological record. We know nothing about how 

 much time elapsed between the formation of the primal crust and 

 the formation of the Algonkian rocks, with their evidences of 

 beginning life, and we know very little of what events transpired 

 during the period. 



The life of the Algonkian era must have consisted mainly of low 

 forms of vegetation with some protozoans, as no other forms 

 could exist under the conditions of those times; and yet in the 

 next higher rocks that have been found there is evidence of an 

 abundance of life of well-advanced forms. The early rocks had 

 been strongly folded and deeply eroded before the later rocks were 

 deposited. Thus the relations of the rocks and the forms of life 

 show that after the formation of the Algonkian rocks there is an 

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