WEALDEN BEDS. 



197 



to the incisors of the rhinoceros, and crested with horns ; — such a 

 creature must have been the iguanodon ! Nor were the inhabitants 

 of the waters much less wonderful ; witness the plesiosaurus, which 

 only requiring wings to be a flying dragon ; the fishes resembling Si- 

 lu?'i, Balista, Another large fossil reptile, scarcely less re- 



markable than the iguanodon, was discovered by Mr. Mantell, in the 

 strata of Tilgate Forest, in 1832. This animal was less than the 

 iguanodon. Mr. Mantell, from his profound knowledge of compa- 

 rative anatomy, has been able to ascertain, that it differs in structure 

 from every known species of living or fossil lizard or crocodile, 

 though it agrees with some of them in many important parts of its 

 osteology. Tt appears to have had a row of scaly fringes on its back 

 some of which are seventeen inches in length : when erected, they 

 must have given the animal a truly terrific appearance. To this 

 new animal Mr. Mantell proposes to give the name of Hylaeosaurus, 

 or Forest lizard. 



In the preceding chapter it was stated, that the Portland oolite 

 composed the upper beds of the oolite formation. The annexed ta- 

 ble will show their position with respect to the Wealden beds, and the 

 chalk formation, in a descending series : 



1. Upper chalk, with flints. 

 Lower chalk and chalk marl. 



2. Upper green sand. 

 Blue clay, called gait. 

 Ferruginous or iron sand. 

 Lower green sand. 



2. Weald clay and sandstone. 



Sand, gritstone, and conglomerate. 



Argillaceous limestone and slaty marl, comprising Purbeck and 

 Petworth limestone. 



The whole supposed to be resting upon the upper or Portland oolite. 

 (See the preceding Chapter.) 



The Purbeck limestone does not occur in the Weald country, 

 though evidently a lower member of that formation. 



According to the tabular arrangenient of the fossils in the difl^erent 

 beds in Sussex, given by Mr. Mantell, the chalk, chalk-marl, green 

 sand, gait, and lower green sand, contain remains of two hundred 

 and ninety-four species of marine animals, and thirteen species of 

 plants, chiefly marine. 



The Wealden beds contain remains of fifty-two species, which, 

 with few exceptions, are either of terrestrial or freshwater animals, 

 and nine species of terrestrial plants. 



Of the numerous species of chambered marine shells, such as 

 nautilites, ammonites, and belemnites, that abound in the secondary 

 strata, below the Wealden, and in the chalk formation above it, not 

 an individual shell has been hitherto found in any part of the Weald 



