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 ; but it must be recol- 
lected, that this relation to the recent epoch is only one of 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 (xticov, minor, and xaivor, 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 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 there are a certain number of fossil species which are 
characteristic of the Pliocene strata before described, so also 
