SUBDIVISIONS IN GEOLOGICAL HISTORY. 



411 



353. 



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Quaternary. 



Tertiary. 



Upper Cretaceous. 



I o I g 



Lower Cretaceous. 



Oolytic Epoch. 



Liassic Epoch. 



Upper. 

 Middle. 

 Lower. 





Recent. 



Champlain. 

 Glacial. 



Pliocene. 



- Neocene. 



Miocene. 

 Eocene. 



Upper or White 

 Chalk. 

 Upper Cretaceous.-^ Lower Chalk, and 

 Marl. 

 .Upper Greensand. 



Lower Cretaceous or Neocomian, in- 

 cluding the Wealden. 



Upper Oolyte. ■ 



Purbeck, Portland, and 

 Kimtneridge Clay. 



Middle Oolyte. jg°-;.-?,-^y. 

 Stonesfield. 



Lower Oolyte. 

 Upper Lias. 

 Marlstone. 

 Lower Lias. 



Keuper. 



Muschelkalk. 



Buntersandstein. 



Inferior Oolyte. 



Agassiz, first at Xeufchatel, in 1841, in a Discours sur la Succession et le 

 Developpement des Etres organises, and later in his Principles of Zoology, 1848, 

 distinguished Paleozoic time, as that of the Reign of Fishes ('^le Regne des 

 Poissons") ; Mesozoic time, as that of the Reign of Reptiles ; and Cenozoic 

 time, as that of the Reign of Mammals. 



Inferior Subdivisions. — The subdivisions under the eras, — the periods, 

 and epochs, — vary, as has been stated, in different countries. The table 

 (Fig. 352) presents a general view of those of eastern North America, so 

 far as the Paleozoic is concerned, — the Silurian, Devonian, and Carbonic 

 heing well represented on the continent. The rest of the series (Fig. 353) is 

 partly from European geology, where the system is well represented. 



In this Manual, American geology is in general first considered ; and 

 afterward such further illustrations are drawn from other continents as are 

 necessary for comprehensive views and generalizations. 



The subdivisions, as the table shows, are named, for the most part, from 

 the locality or region where the rocks are well displayed. Owing to condi- 

 tions explained beyond, the subdivisions of the American Paleozoic series are 



