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THE WONDERS OF GEOLOGY. ' Lect. IV. 



not a vestige of any of the mammalia occurs in the Weal- 

 den deposits. Even these teeth, which so strikingly re- 

 semble the incisors of the Rhinoceros, and these bones of 

 the feet and toes, which are so similar in shape and 

 size to those of the Hippopotamus, belong to oviparous 

 quadrupeds. Many of the specimens can be referred to 

 certain extinct forms of saurians, or lizards ; but the affini- 

 ties of others have not been ascertained. The determination 

 of these fossil bones is indeed no easy task ; for while in 

 many marine deposits, considerable portions of the skeletons, 

 or even the entire series, are often discovered, in the 

 Wealden, with but few exceptions, every bone, tooth, and 

 scale, has been found apart from each other ; and as if to 

 render the task still more perplexing, the relics of several 

 different species and genera are scattered at random through 

 the rocks. Every specimen, too, bears evidence of having 

 been transported from a distance. It would seem as if the 

 limbs and carcasses of the animals had floated down the 

 stream, and been rolled backwards and forwards by the 

 tides, and the bones broken, before they sank down and 

 became imbedded in the mud of the delta. To collect these 

 scattered fragments, and extricate them from the solid rock 

 — to reunite them into a whole, and assign to each skeleton 

 of the respective animals, the bones which once belonged to 

 it, yet not to confound the different species together — such 

 is the labour which the comparative anatomist has to per- 

 form, who undertakes to investigate the nature of the 

 wealden saurians. I reserve for the next Lecture some 

 general observations on the economy and habits of reptiles, 

 and will now describe the fossil relics before us, 



30. Turtles of the Wealden. — The bones and plates 

 of chelonian reptiles are very common in the Purbeck lime- 

 stone, and in the grit, sandstone, and shale of Tilgate 

 Forest. They are referable to two or more freshwater, 

 and one marine species ; one of the former appears to belong 



