588 SCIENTIFIC RECREATIONS. 



Wychwood Forest) is a sandy limestone holding marine fossils. It is used 

 for ornaments. The Coral Rag and Oxford clay are rich in fossils, and the 

 former, as its name implies, is composed of ancient coral reef. The Portland 

 beds produce the well-known building stone. The Purbecks, of which there 

 are three divisions, appear to have been deposited in fresh water, and occur 

 in Dorsetshire. 



All the Oolite strata supply organic remains. We have plants and 

 ferns, reptiles, and a number of new genera of conchifera and cephalopods, 

 star-fish, urchins, and the enormous bats, and the terrible megalosaurus, and 

 the cetiosaurus, steneosaurus, and pliosaurus, of enormous size. One very 

 remarkable bird has been found in the Bavarian limestone of this period ; 

 it is called the Archseopteryx, which is described as having a leg-bone and 

 foot like the familiar birds, but the tail is lizard-like, with feathers springing 

 from each joint. Sponges, corals, and fish, and many other forms of animal 

 life are found in the Oolites. The reptiles must have had it all their own 

 way in this period, for there were both carnivorous and vegetable feeders, 

 and teeth of the pliosaurus have been found which measure fifteen inches, 

 the jaws being six feet long. ' We have seen that corals must have built 

 up their reefs in the waters, which then overlaid the land we call the United 

 Kingdom. 



There must have been great changes during this period, and the strata 

 are chiefly marine. The Wealden formations are the exceptions, and in 

 the fresh-water deposits insect forms abound. The appearance and variety 

 of animal and vegetable life must have been curious and interesting. 



The Weald or " Wold " of Kent is often spoken of, and it extends with 

 the Surrey and Sussex Wealden formations for some distance. The strata 

 are of fresh-water deposition, differing in this from the chalk, although the 

 Wealden beds are included in the Cretaceous Group, which is composed as 

 follows : 



f Wealden. 

 Lower j Greensand. 

 [ "Gault." 

 Upper Greensand. 

 Chalk Marl. 



Upper 



Chalk (without Flint). 

 Chalk (with Flint). 

 Maestricht. 



The " Wealden" formation is divided into Hastings sand and Weald 

 clay. The former consists of clay and sandy beds, and is observable at 

 Hastings, and in the neighbourhood of Tunbridge. The Weald clay consists 

 of blue and brown clays, with sandstone, and the limestone known as 

 " Sussex Marble," which is formed by the paludina of the rivers. There is 

 another division often seen in Dorsetshire, and called the Punfield beds, 

 which partake both of marine and fresh-water remains, which are distinct in 

 the true Wealden and cretaceous formations, the former being of fresh, and 

 the latter of salt-water origin. 



