numbers of the creatures that were permitted to enjoy it, in the multitude of shells and bones preserved in the strata that were deposited during each of the four epochs we are considering.
M. Deshayes and Mr. Lyell have recently proposed a fourfold division of the marine formations of the tertiary series, founded on the proportions which their fossil shells bear to marine shells of existing species. To these divisions Mr. Lyell has applied the terms Eocene, Miocene, Older Pliocene and Newer Pliocene; and has most ably illustrated their history in the third volume of his Principles of Geology.
The term Eocene implies the commencement or dawn of the existing state of the animal creation; the strata of this series containing a very small proportion of shell referable to living species. The Calcaire Grossier of Paris, and the London clay, are familiar examples of this older tertiary, or Eocene formation.
The term Miocene implies that a minority of fossil shells, in formations of this period, are of recent species. To this era are referred the fossil shells of Bordeaux, Turin, and Vienna.
In formations of the Older, and Newer Pliocene, taken together, the majority of the shells belong to living species; the recent species in the newer, being much more abundant than in the older division.
To the Older Pliocene, belong the Sub-apennine marine formations, and the English Crag; and to the Newer Pliocene, the more recent marine deposites of Sicily, Ischia, and Tuscany.[1]
in the second series of the Transactions of the Linnean Society of Normandy.
In the Annals of Philosophy, 1893, the Rev. W. D. Conybeare published an admirable memoir, illustrative of a similar geological map of Europe.
- ↑ The total number of known fossil shells in the tertiary series is 3,036. Of these 1,238 are found in the Eocene; 1,021 in the Miocene; and 777 in the Older and Never Pliocene divisions.
The numerical proportions of, recent to extinct species may be thus expressed.—In the
Newer Pliocene period 90 to 95 Per cent. are of
recent species.Older Pliocene period 35 to 50 Miocene period 18 Eocene period 3½ —Lyell's Geology, 4 Ed. vol. iii. p. 308.
