THE PTERODACTYLS. 317 



sort of connecting link between the three great groups, reptiles, 



birds, and mammals. It seems to have been capable of walking 

 with ease upon the ground, of perching on trees, and of flying 

 swiftly through the air. The teeth of the pterodactyle are long, 

 pointed, and slender, from twenty to thirty in each jaw, and like 

 the crocodile replaced by new ones when worn. While the cal- 

 careous oolitic beds were being deposited in the sea, there seerns 

 to have been in some parts of the world, but particularly in the 

 southern part of England, immense rivers, with extensive estu- 

 aries flowing over vast tracts of countries, and bearing down 

 upon their waters and imbedding in the mud and silt of the shoal- 

 ing estuaries, the remains of land plants and animals, and fresh 

 water shells. To the beds or deposits thus made, the name 

 Wealden has been given, (seo page 188). With the exception 

 of the plants of the coal epoch, this deposit is almost the sole evi- 

 dence of the ancient land and its inhabitants. It is somewhat 

 remarkable that among all the previous deposits no trace of any 

 true quadruped has been found, all the remains belong to marine 

 4^1and reptiles, and up to the time of the Wealden formation no 

 traces except the few tracks on the new red sandstone, are found 

 of birds. Dr. Mantel), who has so successfully investigated the 

 geology of the south-east of England, has however in the latter 

 flamed strata, discovered many fragments of bones supposed to 



