MESOZOIC TIME. 485 



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

 saurs, in the Jurassic ; and this type continued into the Cretaceous, 

 but then ended. 



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

 cline. The Reptilian type was unfolded in its complete diversity : 

 the sea, air, and earth had each its species ; and there were both grazing 

 and carnivorous kinds, of large and small dimensions. Not only every 

 species, but also every Mesozoic genus, with perhaps one or two ex- 

 ceptions, became extinct at or near the close of the era. 



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 all the world. 



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 Dinosaurs, 

 twenty to fifty feet long, ten or twelve Crocodilians, Lacertians, and 

 Enaliosaurs, ten to fifty or sixty feet long, besides Pterodactyls and 

 Turtles. As only part of the species in existence would have left 

 their remains in the rocks, it would be evidently no exaggeration 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 Britain. In 

 India, or the Continent of Asia, there are but two species over fifteen 

 feet long ; in Africa, but one ; in all America, but three ; and not 

 more than six in the whole world ; and the length of the largest does 

 not exceed twenty-five feet. The number of living species exceeding 

 ten feet in length, is only sixteen or eighteen. 



The Galapagos Islands are strikingly Reptilian at the present time. 

 But they afford only four Lizards, as many Snakes, a Turtle, and a 

 large Tortoise. The largest of the lizards, an aquatic species, of the 

 genus Amblyrhynchus (having feet, however, instead of paddles), is but 

 three to four feet long. 



If so large a number of species as above mentioned existed in Brit- 

 ain and its vicinity during the age of Reptiles, what should be the 

 estimate for the whole world at that time ? The question is a good 

 one for consideration, although no definite reply can be looked for. 



As in the case of Mollusks, the culmination of the grand type does 

 not imply a culmination of all its subdivisions. There is no evidence 

 that the Mesozoic species of Turtles are superior in grade to those of 

 the Cenozoic and the present age. 



Birds. — Birds probably began in the Triassic, for, although the 

 evidence from tracks in the Connecticut Valley Sandstone is doubtful, 



