226 THE STOEY OF THE EAETH AND MAN. 



much of the aspect of those of the present day, 

 that an ordinary observer, if he could be shown a 

 quantity of Jurassic or Cretaceous crabs, lobsters, 

 and shrimps, would not readily recognise the differ- 

 ence, which did not exceed what occurs in distant 

 geographical regions in the present day. The same 

 remark may be made as to the corals of the 

 Mesozoic ; and with some limitations, as to the 

 star-fishes and sea-urchins, which latter are espe- 

 cially numerous and varied in the Cretaceous age. 

 In short, all the invertebrate forms of life, and 

 the fishes and reptiles among the vertebrates, had 

 already attained their maximum elevation in the 

 Mesozoic; and some of them have subsequently 

 sunk considerably in absolute as well as relative 

 importance. 



In the course of the Mesozoic, as indicated in the 

 last chapter, there had been several great depressions 

 and re-elevations of the Continental Areas. But these 

 had been of the same quiet and partial character with 

 those of the Palaeozoic, and it was not until the close 

 of the Mesozoic time, in the Cretaceous age, that a 

 great and exceptional subsidence involved for a long 

 period the areas of our present continents in a sub- 

 mergence wider and deeper than any that had pre- 

 viously occurred since the dry land first rose out of 

 the waters. 



Every one knows the great chalk beds which ap- 

 pear in the south of England, and which have given its 

 name to the latest age of the Mesozoic. This great 



