522 



CENOZOIC TIME. 



hence it is that traces of the Cretaceous fauna are found in the Terti- 

 ary beds, even through the whole of the Lignitic Eocene. 



With the opening of the second period of the North American Ter- 

 tiary, the Alabama period, the continent had nearly the form repre- 

 sented on the accompanying map, as shown by the distribution of the 

 areas covered by marine beds. The Atlantic Border was submerged, 

 nearly as in the Cretaceous period : there was no Delaware or Chesa- 

 peake Bay, and no Peninsula of Florida. The Mexican Gulf spread 

 far beyond its present limits north and west, but not, as in the pre- 

 ceding era, over the Rocky Mountain slopes. The Ohio and Missis- 

 sippi were barely united at their mouths, if not wholly disjoined. 

 Owing to the elevation of the land westward, the Missouri and other 

 streams rising in the mountains had begun to exist. Yet this eleva- 

 tion was small; and, as Hay den has rightly inferred from the great 

 fresh-water Tertiary deposits, the country was mostly covered by vast 

 fresh-water lakes. 



After the close of the Vicksburg epoch, referred to the Upper Eo- 

 cene, there appears to have been a further reduction of the Mexican 

 Gulf ; for no later marine Tertiary beds are recognized on its borders. 

 The " Grand Gulf beds," described by Hilgard as covering a coast re- 

 gion, south of Vicksburg, appear, as he observes, to indicate that, for a 

 period after the Eocene and before the Quaternary, the coast line 

 was along their northern border ; but no marine fossils occur in them, 

 and the particular period to which the beds belong is uncertain. 



The Atlantic Tertiary region must have remained submerged until 

 after the Miocene era. The absence, from most parts of the coast, of 

 deposits that can properly be identified as Pliocene is a remarkable 

 fact, and seems to show that the continent, during the Pliocene era, had 

 at least its present breadth along the larger part of the Atlantic coast, 

 if not a still greater eastward extension. 



The change of water-level, which caused this enlargement of the 

 area of dry land, was probably not confined to the border of the con- 

 tinent, but was part of a general change, in which a large part of the 

 continent partook, especially the Pocky Mountain region. 



2. European Geography. — In the earliest epoch of the Tertiary, 

 in Europe, there appears to have been, as has been observed by others, 

 first, an emergence of the land from the Cretaceous seas, when the 

 Chalk formation was eroded at surface, and a flint conglomerate in 

 some places formed ; and when, moreover, in some parts, Lignitic beds 

 were made, as in America. The return of the land to the sea-level, 

 and in some places to beneath it, commenced the formations of the ma- 

 rine and estuary Tertiary of the succeeding epoch ; and a still more 

 general submergence brought about the state when the great Nummu- 



