498 MESOZOIC TIME — REPTILIAN AGE. 



which first appeared in the Carboniferous, have gigantic species in 

 the Triassic, and at its close cease. The type of Amphibians is 

 afterwards represented only by small species of the ordinary type 

 without scales. 



Culmination of the type of True Reptiles. — The Enaliosaurs or Swim- 

 ming Saurians of the Triassic — the Nothosaur type — have the open 

 skull of a Batrachian. In the Jurassic the type rises to the higher 

 grade of the Ichthyosaurs and Plesiosaurs, when there were several 

 genera and numerous species. In the Cretaceous the species are 

 very few ; afterwards there were none. 



The Lacertians commence in the later Palaeozoic, in species with 

 the ichthyic characteristic of biconcave vertebrae, and retain it 

 through the Triassic and in some Jurassic species. In the Jurassic 

 and Cretaceous they come forth in many other species of great size 

 without this low feature. After the Cretaceous only smaller species 

 exist. 



The Saurian type in the later Jurassic rises also to the grade of 

 Dinosaurs, the highest in rank and among the largest of Keptiles ; 

 and these all disappear before the close of the Cretaceous period. 



There is also an expansion of the type to flying forms, the Ptero- 

 saurs, in the Jurassic, and this type continues into the Cretaceous, 

 but then ends. 



Thus, in all the grand divisions there was a culmination and 

 decline. Every genus becomes extinct at the close of the era 

 except that of Crocodilus, which began in its last period. 



The Reptilian type was unfolded in its complete dimensions, so 

 as to parallel the later expansion of Mammals. The sea, air, and 

 earth had each its species, and there were both grazing and carni- 

 vorous kinds of large and small dimensions. 



The reality of this Reptilian feature of the age will appear from a 

 comparison of England as it was in Reptilian times with England 

 as it is, or with India, Africa, and America. 



In a single era, that of the Wealden and Lower Cretaceous, — for 

 the two were closely related in vertebrate species, — there were in 

 the British dominions of sea and land four or five species of Dino- 

 saurs twenty to fifty feet long, ten or twelve Crocodilians, Lacer- 

 tians, and Enaliosaurs, ten to fifty or sixty feet long, besides Ptero- 

 dactyls and Turtles. As only part of the species in existence would 

 have left their remains in the rocks, it would be evidently no exagge- 

 ration to increase the above numbers two or three fold. But, taking 

 them as made out by actual discovery, the facts are sufficient to 

 establish the contrast in view. For, since man appeared, there is 

 no reason to believe that there has been a single large Reptile in 



