412 THE WONDERS OF GEOLOGY. Lect. IV. 



and plastron of a true marine turtle, belonging to a species 

 three feet in length, was obtained from the sandstone of 

 Tilgate Forest many years since, and some fragments are 

 figured in my early works on the fossils of that district.* 



31. Marine reptiles of the Wealden. — By far the 

 greater part of the bones obtained from the quarries of 

 Tilgate Forest, Horsham, &c. belong to colossal terres- 

 trial reptiles ; but with these are associated the osseous 

 remains of two or three genera, which there is every reason 

 to suppose were inhabitants of the sea into which the river 

 flowed, that deposited the strata of the Wealden. 



Plesiosaurus. I have collected from various Sussex 

 localities, bones of the extremities and cervical and caudal 

 vertebrae, of one or more species of the extraordinary 

 marine reptile called Plesiosaurus, whose remains are 

 found in such prodigious quantities in the Lias and Oolite ;f 

 thus, we have proof that this animal was at least an occa- 

 sional visitant of the bays and estuaries of the Wealden river. 



Cetiosaurus.% Some of the largest vertebrae and bones 

 found in the Wealden strata belong to an aquatic reptile, 

 probably of marine habits, of which numerous bones occur 

 in the oolite of Oxfordshire, Northamptonshire, &c. The 

 vertebrae are distinguished by their nearly circular faces, 

 and relatively short bodies ; in the dorsal the anterior face 

 is nearly flat, and the posterior concave ; but in the caudal 

 both are concave, with a well-defined border, which gives 

 the body a deeply excavated character. Some specimens 



* Medals of Creation, vol. ii. p. 776. Fossils of Tilgate Forest, 

 PI. VII. fig. 2. 



f Fossils of Tilgate Forest, PL IX. figs. 4, 5. 



% The name implies the affinity of these reptiles to the cetaceans. 

 See Medals of Creation, vol. ii. p. 726. No vestiges of true ceta- 

 ceans have been found in a fossil state in strata older than the tertiary 

 it would seem that the advent of the terrestrial and aquatic mam- 

 malia on our globe, took place contemporaneously. 



