222 GEOLOGICAL SUCCESSION OF ANIMALS. 



to those of the Oolitic formation, which immediately precedes, 

 than to those of the carboniferous formation, which is much 

 more ancient; and, in the same manner, the fossils of the 

 carboniferous group approach more nearly to those of the 

 Silurian formation than to those of the Tertiary. 



468. These relations could not escape the observation of 

 naturalists, and indeed they are of great importance for the 

 true understanding of the development of life at the surface 

 of our earth. And, as in the history of man, several grand 

 periods have been established, under the name of Ages, 

 marked by peculiarities in his social and intellectual condi- 

 tion, and illustrated by contemporaneous monuments, so, in 

 the history of the earth, also, are distinguished several great 

 periods, which may be designated as the various Ages of 

 Nature, illustrated, in like manner, by their monuments, the 

 fossil remains, which, by certain general traits stamped upon 

 them, clearly indicate the eras to which they belong. 



469. We distinguish four Ages of Nature, corresponding 

 to the great geological divisions, namely : 



1st. The Primary or Palceozoic Age, comprising the lower 

 Silurian, the upper Silurian, and the Devonian. During this 

 age there were no air-breathing animals. The fishes were 

 the masters of creation. We may therefore call it the Reign 

 of Fishes. 



2d. The Secondary Age, comprising the carboniferous for- 

 mation, the Trias, the Oolitic, and the Cretaceous formations. 

 This is the epoch in which air-breathing animals first appear. 

 Reptiles predominate over the other classes, and we may 

 therefore call it the Reign of Reptiles. 



3d. The Tertiary Age, comprising the tertiary formations. 

 During this age, terrestrial mammals, of great size, abound. 

 This is the Reign of Mammals. 



4th. The Modern Age, characterized by the appearance 

 of the most perfect of all created beings. This is the Reign 

 of Man. 



