Ch. XVIII.] WEALDEN GROUP. 349 



The picturesque scenery of the " High Rocks " and other places 

 in the neighborhood of Tunbridge is caused by the steep natural 

 cliffs, to which a hard -be of white sand, occurring in the upper part of 

 the Tunbridge "Wells Sand, mentioned in the preceding table, gives rise. 

 Mr. Drew found this bed of " rock-sand " to vary in thickness from 25 

 to 48 feet. Large masses of it, which were by no means hard or 

 capable of making a good building-stone, form, nevertheless, project- 

 ing rocks with perpendicular faces, and resist the degrading action 

 of the river because, says Mr. Drew, they present a solid mass with- 

 out planes of division.* The calcareous sandstone and grit of Til- 

 gate Forest near Cuckfield, in which the remains of the Tguanodon and 

 Hylseosaurus were first found by Dr. Mantell, constitute an upper 

 member of the Tunbridge "Wells Sand, while the " sand-rock " of the 

 Hastings cliffs, about 100 feet thick, is one of the lower members of 

 the same. The reptiles, which are very abundant in this division, 

 consist partly of saurians, referred by Owen and Mantell to eight 

 genera, among which, besides those already enumerated, we find the 

 Megalosaurus and Ple'siosaurus. The Pterodactyl also, a flying rep- 

 tile, is met with in the snme strata, and many remains of Chelonians 

 of the genera Trionyx and Emys, now confined to tropical regions. 



The fishes of the Wealden are chiefly referable to the Ganoid and 

 Placoid orders. Among them the teeth and scales of Lepidotus are 

 most widely diffused (see fig. 343). These ganoids were allied to the 



Fig. 848. 



» 



Zepidotus JfanteUi, Agass. Wealden. 

 a. Palate and teeth. 6. Side view of teeth. c. Scale. 



Lepidosteus, or Gar-pike, of the American rivers. The whole body was 

 covered with large rhomboidal scales, very thick, and having the ex- 

 posed part coated with enamel. Most of the species of this genus are 

 supposed to have been either river-fish, or inhabitants of the sea at the 

 mouth of estuaries. 



The shells of the Hastings beds belong to the genera Melanopsis, 

 Melania, Paludina, Cyrena, Cyclas, Vnio (see fig. 344), and others, 

 which inhabit rivers or lakes ; but one band has been found at Pun- 

 field, in Dorsetshire, indicating a brackish state of the water, where 

 the genera Corbula (see fig. 345), Mytilus, and Ostrea occur ; and in 



* Quart. Geol. Journ., 1861, vol. xvii. p. 274. 



