§12. CLASSIFICATION OF THE TERTIARY. 215 



researches ; and the relative proportions of recent and 

 extinct organisms, may be found to occur in a very different 

 ratio, from that which is assumed as the basis of this 

 arrangement.* 



12. Classification of the tertiary. — According to 

 this system the tertiary strata form three principal groups, 

 each characterized by the relative proportion of the recent 

 and extinct species of shells ; and a nomenclature has been 



* This anticipation is already in some measure confirmed; for 

 existing species have been found in the most ancient tertiary de- 

 posits : and several secondary shells, fishes, &c. in tertiary strata, 

 and even living in the present seas. An eminent Italian naturalist 

 (Dr. A. Philippi), in an elaborate review of the mollusca of the South 

 of Italy in reference to the shells of the tertiary period, has come to 

 the following conclusion :— * That the tertiary formations of Southern 

 " Italy will not admit of any chronological subdivisions, for we cannot 

 " trace the limits which separate the tertiary from the diluvial, nor 

 " the diluvial from the existing period ; neither can we make use of 

 " the terms eocene, miocene, and pliocene, with reference to the South 

 " Italian deposits, so far as these expressions refer to a per centage of 

 " extinct to existing species ; and we would suggest that such terms 

 " are also uncertain and arbitrary with regard to other districts." — 

 Philippi: Proceed. Geol. Soc. Feb. 1846. 



Immediately after the last tertiary deposits, the modern period 

 begins, when all the now European species first appear^ the cavern 

 animals and some of the large pachyderms, are referable to the earliest 

 age of this era. Inundations, more or less local, occasioned by the 

 elevation of some tracts of dry land, and the subsidence and submer- 

 gence of others, filled up the caverns and destroyed the races of car- 

 nivora. 



In the diluvial gravel in the Canton of Geneva, there have been found 

 bones of many species of animals which still inhabit the surrounding 

 country ; as for example, the mole, fox, sheep, ox, pig, rat, mouse, 

 green frog, lizard, &c. These remains occur beneath distinctly strati- 

 fied beds of gravel, at a depth of ten feet below the cultivated soil. 

 These animals must therefore have been indigenous to this part of 

 Europe, when the deposition of the diluvium was going on, and prove 

 the continuance of species uninfluenced by those geological changes 

 which occasioned the last elevation of the land. — M. Pictet on the 

 Diluvial Deposits of the Canton of Geneva, 



