THE NEOZOIC AGES. 241 



done in the following sketches : 1 . Tho seas of the 

 Eocene. 2. Mammals from the Eocene to the Modern. 

 3. Tertiary floras. 4. The Glacial period. 5. The 

 Advent of Man. 



The great elevation of the continents which closed 

 the Cretaceous was followed by a partial and unequal 

 subsidence, affecting principally the more southern 

 parts of the land of the northern hemisphere. Thus, 

 a wide sea area stretched across all the south of 

 Europe and Asia, and separated the northern part of 

 North America from what of land existed in the 

 southern hemisphere. This is the age of the great 

 Nummulitic Limestones of Europe, Africa, and Asia, 

 and the Orbitoidal Limestones of North America. The 

 names are derived from the prevalence of certain 

 forms of those humble shell-bearing protozoa which 

 we first met with in 'the Laurentian, and which we 

 have found to be instrumental in building up the 

 chalk, the Foraminifera of zoologists. (Fig. p. 243.) 

 But in the Eocene the species of the chalk were re- 

 placed by certain broad flat forms, the appearance of 

 which is expressed by the term nummulite, or money- 

 stone; the rock appearing to be made up of fossils, 

 somewhat resembling shillings, sixpences, or three- 

 penny pieces, according to the size of the shells, each 

 of which includes a vast number of small concentric 

 chambers, which during life were filled with the soft 

 /elly of the animal. The nummulite limestone was 

 undoubtedly oceanic, and the other shells contained 

 iii it, are marine species. After what we have already 



