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Show 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 speci~s. It will. be seen .t~~t of two hundred and twenty-six spectes, found m the S1Cthan beds, only ten are of extinct or unknown species, although the antiquity of these tertiary deposits, as contrasted with our most remote historical eras, is immensely gt·eat. 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 Olde·r Pliocene. To the latter belong the formations of Tuscany, and of the Subapennine 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; but it must be recollected, that this relation to the recent epoch is only one of its zoological characters, and that certain peculiar species of testacea also distinguish its deposits from all other strata. The relative position of the beds referrible to this era has been explained in diagrams Nos. 3 and 4, letter f, chapter II. JHiocene period.-The next antecedent tertiary epoch we shall name Miocene, from f.J. EIOJV, minor, and xatvos, 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 10~1, of which one hundred and seventy-six only are recent, being in the proportion of rather less than 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 ther~ are a certain number of fossil species which are characteristic of the Pliocene ~trata before des9rib~d 7 so also o6h. V.] TilE TERTIARY EPOCH. 55 there are many shells exclusively confined to the Miocene period. We have already stated, that in Touraine and in the South of France near Bordeaux, in Piedmont, in the basin of Vienna, and other localities, these Miocene formations are largely developed, and their relative position has been shown in diagrams Nos. 3 and 4, letter e, chapter II. Eocene pe·riod.-The period next antecedent we shall call Eocene, from iJo;r, aurora, and xatvos, recens, because the extremely small proportion of living species contained in these strata, indicates what may be considered the first commencement, or dawn, of the existing state of the animate creation. To ~his era the formations first called tertiary, of the Paris and London basins, are referrible. Their position is shown in the diagrams Nos. 3 and 4, letter d, in the second chapter. The total number of fossil shells of this period already known, is one thousand two hundred and thirty-eight, of which number forty-two only are living species, being nearly in the proportion of three and a half in one hundred. Of fossil species, not known as recent, forty-two are common to the Eocene and Miocene epochs. In the Paris basin alone, 11~~ species have been found fossil, of which thirty-eight only are still Jiving. The geographical distribution of those recent species which are found fossil in formations of such high antiquity as those of the Paris and London basins, is a subject of the highest interest. It will be seen by reference to the tables, that in the more modern formations, where so large a proportion of the fossil shells belong to species still living, they also belong, for the most part, to species now inhabiting the seas immediately adjoining the countries where they occur fossil; whereas the recent species, found in the older tertiary strata, are frequently inhabitants of distant latitudes, and usually of warmer climates. Of the forty-two Eocene species, which occur fossil in England, France, and Belgium, and which are still living, about half now inhabit within, or near the tropics, and almost all the rest are denizens of the more southern parts of Europe. If some |