14 INTRODUCTION. 



are found so high up as the London Clay ; and to the de- 

 posits superior to this, the genus is entirely wanting. Nearly 

 the same observations extend to the genera Orthocera, 

 Belemnites and Hamites. We look to the Tertiary Forma- 

 tion with peculiar interest, as its lower deposit or period 

 contains the incipient state, or as Mr Lyell says, "the 

 dawn of the existing state of the animate creation." 



The division of the Tertiary Formation into three epochs, 

 has been admitted by most modern geologists. For these, 

 Mr Lyell* proposes, in the descending order, the names of 

 Pliocene period, Miocene period, and Eocene period. The 

 first is derived from the Greek words vxttuv major, and KO.IVOS 

 recens, as most of them are recent species, and of course, 

 of later deposit. This he subdivides into the Newer and 

 Older Pliocene, in which division M. Deshayes does not 

 agree with him. The second, Miocene, is from ^UM 

 minor, and *<moc recens, there being here a minority of 

 recent species. The third, the Eocene, is derived from 5 

 aurora, and *<w recens, this being " the dawn of the 

 existing state of the animate creation." 



In the lowest of these, the Eocene period,! there have 

 been observed in Europe one thousand two hundred and 

 thirty-eight species, of which the very small number of 

 forty-two have been identified with recent species. " Of 

 fossil species, not known as recent, forty-two are common 

 to the Eocene and Miocene epochs.":): It is remarkable, 

 too, that the living species are rarely inhabitants of the 

 shores of those countries in which they are found in a 

 fossil state, inhabiting now more southern climates. 



The next period of deposit, that of the Miocene, is a for- 



* Principles of Geology, vol. 3, p. 53. 



t Mr. Lyell, with great propriety, includes in this period the Plaslic 

 Clay with the London Clay ; the line of separation of which, he says, 

 " is quite arbitrary." Principles of Geology, vol. 3, p. 278. 



t Principles of Geology, vol. 3, p. 55. 



