530 



CENOZOIC TIME — MAMMALIAN AGE. 



boscis, being in some points between the Stags and the Pachyderms. It is sup- 

 posed to have had the bulk of an elephant and greater height. Bos and the 

 related genera probably occur nowhere earlier than the Pliocene and Post- 

 tertiary. 



General Observations. 



1. American Geography. — The general form of the North Ame- 

 rican Continent on the east during the early part of the Tertiary 

 period is shown by the distribution of the areas covered by marine 

 beds on the map, p. 133. From such data the following map has 

 been constructed. The Atlantic border was submerged nearly as in 



Fig. 828. 



North America in the Period of the Early Tertiary. 



the Cretaceous period ; there was no Delaware or Chesapeake Bay, and 

 no Peninsula of Florida. The Mexican Gulf spread far beyond its 

 present limits north and west, but not over the Eocky Mountain 

 slopes as in the preceding era. The Ohio and Mississippi were barely 

 united at their mouths, if not wholly disjoined. Owing to the ele- 



