SIXTH CRETACEOUS PERIOD. 



submerged. Great changes were also produced at other points. Thus 

 it was at the commencement of this period, that in consequence of 

 a considerable subsidence of the land, the sea flowed over all 

 Belgium as far as Maestricht, cover- 

 ing land which had remained dry 

 since the close of the Palaeozoic age. 

 It was also during this period that 

 the sea extended its limits from 

 Snowdon to the Ural Mountains, over 

 an extent of 40 of longitude. It 

 al>o covered a surface of 30 upon the 

 southern coast of South America. It 

 covered also Chili in the western 

 continent, and Pondicherry in the 

 eastern. From the identity of the 

 marine deposits, it may be inferred 

 that the sea of this period extended 

 without interruption from France to 



all those distant points and from the tropics to the 56 D north, and 

 the 3i of south latitude. 



Fig. 177. Spondylus spinosus. 



Fig. 178. Reticulopora obliqua. 



The land underwent changes corresponding with those of the 

 seas, being everywhere augmented where the seas retired, and 

 diminished where they advanced. 



447. The Cycloid and Ganoid fishes prevailed in great numbers 

 i 2 115 



