AGES OF NATURE. 397 



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

 age there were few 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, 

 the trias, the oolitic, and the cretaceous formations. This 

 is the epoch in which air-breathing animals more extensively 

 prevail. The 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. 



v / 



4th. The Modern Age, characterized by the appearance of 

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

 Man. 



Let us review each of these four Ages of Nature, with re- 

 ference to the diagram at the beginning of the volume. 



659. THE PALEOZOIC AGE. Reign of Fishes. The 

 palaeozoic fauna, being the most remote from the present epoch, 

 presents the least resemblance to the animals now existing, as 

 will easily be perceived by a glance at the following sketches 

 (fig. 377). In no other case do we meet with animals of 

 such extraordinary shapes, as in the strata of the palaeozoic 

 age. 



660. We have already stated ( 655) that there are found, 

 in each formation of the primary age, animal remains of all 

 the four great departments, namely, vertebrata, articulata, 

 mollusca, and radiata. We have now to examine to what 

 peculiar classes and families of each department these remains 

 belong, with a view to ascertain if any relation between the 

 structure of an animal and the epoch of its first appearance 

 on the earth's surface may be traced. 



661. As a general result of the inquiries hitherto made, 

 it may be stated that the palaeozoic animals belong, for the 

 most part, to the lower divisions of the different classes. 

 Thus, of the class of echinoderms, we find scarcely any but 

 Crinoids (figs. 72 and 73), which are the least perfect of the 

 class ; of which there are some quite peculiar types from, the 

 Trenton limestone and from the Black River limestone. 



662. Of the mollusca, the bivalves or acephala are nu- 

 merous, but for the most part belong to the brachiopoda, that 

 is to say, to the lo^u-est division of the class, including molluska 



