54 SUBDIVISIONS OF [Ch. V. 



The newer Pliocene formations, before alluded to, pass in- 

 sensibly into those of the Recent epoch, and contain an immense 

 preponderance of recent species. It will be seen that of two 

 hundred and twenty-six species, found in the Sicilian beds, 

 only ten are of extinct or unknown species, although the anti- 

 quity of these tertiary deposits, as contrasted with our most 

 remote historical eras, is immensely great. In the volcanic 

 and sedimentary strata of the district round Naples, the pro- 

 portion appears to be even still smaller. 



Older Pliocene period. These formations, therefore, and 

 others wherein the plurality of living species is so very decided, 

 we shall term the Newer Pliocene, while those of the tertiary 

 period immediately preceding may be called the Older Pliocene. 

 To the latter belong the formations of Tuscany, and of the Sub- 

 apennine hills in the north of Italy, as also the English Crag. 



It appears that in the period last mentioned, the proportion 

 of recent species varies from upwards of a third to somewhat 

 more than half of the entire number ; liut it must be recol- 

 lected, that this relation to the recent epoch is^o^jiniof its 

 zoological characters, and that certain peculiar species of, tes- 

 tacea also distinguish its deposits from all other strata. The 

 "relative position of the beds referrible to this era has been ex- 

 plained in diagrams Nos. 3 and 4, letter/, chapter II. 

 , Miocene period. The next antecedent tertiary epoch we 

 shall name Miocene, from /w,ewv, minor, and xatvor, recens, a 

 minority only of fossil shells imbedded in the formations of this 

 period, being of recent species. The total number of Miocene 

 shells, referred to in the annexed tables, amounts to 1021, of 

 which one hundred and seventy-six only are recent, being in 

 the proportion of rather_ Jessjhan eighteen in one hundred. 

 Of species common to this period, and to the two divisions of 

 the Pliocene epoch before alluded to, there are one hundred and 

 ninety-six, whereof one hundred and fourteen are living, and 

 the remaining eighty-two extinct, or only known as fossil. 



As there are a certain number of fossil species which are 

 characteristic of the Pliocene strata before described, so also 



