218 PETRIFACTIONS AND THEIR TEACHINGS. CHAP. III. 



It is obvious, were the Forest Range of the county of 

 Sussex swept away by the encroachments of the sea, and the 

 area it occupied buried beneath the waves, the North Downs 

 would present a strict correspondence in geological structure 

 with the Isle of Wight ; for a portion of the Wealden would 

 appear on the south shore at the base of the chalk escarp- 

 ment, and be succeeded on the north by the greensand, gait, 

 firestone, marl, and white chalk ; and the latter surmounted 

 by tertiary deposits. 1 



FAUNA AND FLORA OF THE WEALDEN. The most important 

 organic remains of the animal kingdom imbedded in the 

 Wealden strata are, unquestionably, in a physiological point 

 of view, the teeth and bones of the colossal terrestrial 

 reptiles, which in their osteological characters approach nearer 

 to the mammalian type than any of the existing species 

 of oviparous quadrupeds. But as these are the relics of 

 land animals transported from a distance and imbedded in 

 the sediments brought down by the waters, they yield but 

 little aid to the geological inquirer in his attempts to deter- 

 mine the origin and formation of the rocks and strata. The 

 vestiges of the beings which inhabited the waters by which 

 the sediments were deposited, can alone afford information as 

 to the physical conditions which then prevailed. Hence, the 

 durable remains of zoophytes, echinoderms, mollusks, crusta- 

 ceans, fishes, and aquatic reptiles, are the objects to which 

 the geologist more particularly directs his attention ; and 

 shells, from their durability, and the indications they afford 

 as to the structure and economy of the animals that inha- 

 bited them, are sought for with avidity. 



I have already mentioned how much the absence of marine 

 shells and corals in the Wealden contributed to awaken my 



1 For fuller information on the subjects embraced in this sketch, see 

 " Elements of Geology," by SIR CHARLES LYELL ; and the " Geology of 

 the South-East of England," or the " Wonders of Geology," by the 

 Author; or "Geological Excursions round the Isle of Wight," &c. 

 2d. edit., 1851. 



On the elevation of the Wealden, and the consequent changes in the 

 relative level of the sea and land, consult the masterly paper of 

 MR. HOPKINS, President of the Geological Society, " On the Geological 

 Structure of the Wealden District and of the Bas Boulonnais," (" Geol. 

 Trans." vol. vii.) ; and Mr. J. P. MARTIN'S beautiful volume, " On the 

 Geological Phenomena of Western Sussex," Pulborough, 1 vol. 4 to, 

 with Maps and Sections. 



