146 THE STORY OF THE EARTH. 



The Wealden strata exhibit two types. In 

 Dorsetshire and in the Isle of Wight they com- 

 prise alternations of numerous beds of grit, sand 

 and clay, frequently of the most brilliant red 

 colour. A few marine shells, species of Pecten, 

 occur in the lower Wealden beds of the Isle of 

 Purbeck. In the Isle of Wight they have yielded 

 multitudes of vegetable remains, among which 

 are pine cones, and especially the fossil forest of 

 >k, where, however, the great forest trees ap- 

 pear to be drifted and water-logged. In these 

 beds have been found the remains of many 

 extraordinary terrestrial reptiles. The OmitJio- 

 ehtirus type of Pterodactyl appears, which has the 

 earlier joints of the backbone blended together, 

 as in the frigate bird. There is a terrestrial 

 ian named Polacanthus, which had the lower 

 part of the body covered with a complete shield 

 like that of an armadillo. Associated with it is 

 the Belgian Tguanodon^ the great Cetiosaurian 



named Ornithopsis, and the genera named Jfypsih- 

 phoJ<>n, SpkenospondyluS) Vectisaurus } etc. 



Further to the north, in the typical Wealden 

 country of Kent, Surrey, and Sussex, these beds, 

 instead of being multitudinous and irregular, he- 

 ated into great divisions of tolerably 

 uniform mineral character. The Ashdown Sand 



is in the main a hard yellow Sandstone. I 

 Wadhurst Clay above it is a number of alterna- 

 tions of shale and hardened sand frequently 



fen 5, with plant remains. The Tunbridge 



(Veils Sand is about 150 feci of sandstone m 

 or less divided by thin beds of claw which may 



these beds, which are 

 ed l tastinj I, comes I he W i-a'.A ( 'lay, 



winch is 900 feet thick in the south-east of Kent, 



