PALEOZOIC TIME — CARBONIC. 



735 



ISTearly all the western lialf of tlie continent was still a sea of varying 

 depth, with perhaps its widespread, sand flats. Only one large dry-land addi- 

 tion to the western part of the continental area is known to have taken place ; 

 it occupied, as shown by King, a portion of the Great Basin, over what is 

 now eastern and central Nevada, having the meridian of 117-|-° W. near its 

 western limit. The western semi-continent was yet to be supplied with thick 

 rock-formations and with its grander mountains ; and veins of gold, silver, 

 and other metals were to be formed, and coal-beds to be accumulated, before 

 finally the emergence of " the Great West " from the waters was completed. 



1155. 



Map of North America after the Appalachian Revolution. 



Disappearance of life. — The disappearance of life at the close of Pale- 

 ozoic time was so general and extensive that no Carboniferous species is 

 known to occur among the fossils of succeeding beds, not only in America 

 and Europe, but also over the rest of the world. The fact is learned better 

 from Europe than from America; for in Europe remains of marine life occur 

 in beds representing the early part of the following period, while in America, 

 the first marine fossil known from the Atlantic border is of the Cretaceous 

 period. A large part of the old tribes of the sea and land continues on, spe- 

 cies having survived through the time of catastrophe ; and yet their species 

 did not find burial among later fossils. Many underwent modifications and 

 appear later under new forms, and thereby as new species. The Cycads and 

 Yews were among the tribes of plants which were continued and increased 

 to a later culmination. Some of the Corals of the Paleozoic belong to the 



