98 VESTIGES OF THE 



styled the saurodoii, from the Uzard-Hke churacter of 

 its teeth. 



We have seen that footsteps of birds are considered to 

 have been discovered in America, in the new red sand- 

 stone. 8ome simihir isolated phenomena occur in tlie 

 subsequent formations. Br. Mantell discovered some 

 bones of birds, apparently w.-iders, in tlie Wealden. Tho 

 immediate connexion of that set of birds with land, may 

 account, of course, for their containing a terrestrial organic 

 relic, which the marine beds above and below did not 

 possess. In the slate of Glaris, in Switzerland, cor- 

 responding to the English gait, in the chalk formation, 

 the remains of a bird have been found. From a chalk 

 bed near Maidstone, have likewise been extracted some 

 remains of a bird, supposed to have been of the long- 

 winged swimmer family, and equal in size to the albatross. 

 These, it must be owned, are less sti-ong traces of the 

 birds than we possess of the reptiles and otliei- tribes ; 

 but it must be remembered that the evidence of fossils, 

 as to the absence of any class of animals from a certain 

 period of the earth's history, can never be considered as 

 more than negative. Animals, of which we find no 

 remains in a particular formation, may, nevertheless, 

 have lived at the time, and it may have only been from 

 unfavourable circumstances that their remains have not 

 been preserved for our inspection. The single circum- 

 stance of their being little liable to be carried do\\'n 

 into seas, might be the cause of their non-appearance in 

 our quarries. There is at the same time a limit to 

 uncertainty on this p(nnt. We see, from what remain> 

 have been found in tlie whole series, a clear ])rogress 

 throughout, from humble to superior tyi)es of being. 

 Hence we derive a light as to what animals may have 



