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 shells referrible 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 the 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 belongs 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-apen

nine marine formations, and the English Crag; and to the Newer Pliocene, the more recent marine deposits of Sicily, Ischia, and Tuscany.*

Alternating with these four great marine formations above the chalk, there intervenes a fourfold series of other strata, containing shells which show them to have been formed in fresh water, accompanied by the bones of many terrestrial and aquatic quadrupeds.

The greater number of shells, both in the fresh-water and marine formations of the tertiary series, are so nearly allied to existing genera, that we may conclude, the animals by which they were formed, to have discharged similar functions in the economy of nature, and to have been endowed with the same capacities of enjoyment as the cognate mollusks of living species. As the examination of these shells would disclose nearly the same arrangements and adaptations that prevail in living species, it will be more important to investigate the extinct

* 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 Newer Pliocene divisions. The numerical proportions of recent to extinct species may be thus expressed.-In the

Newer Pliocene period.... 90 to 95
Older Pliocene period...

35 to 50

--Lyell's Geology, 4. Ed. vol. iii. p. 308.

Per cent. are of recent species.

genera of the higher orders of animals, which seem to have been constructed with a view to the temporary occupation of the earth, whilst the tertiary strata were in process of formation. Our globe was no longer tenanted by those gigantic reptiles, which had been its occupants during the secondary period; neither was it yet fit to receive the numerous tribes of terrestrial mammalia that are its actual inhabitants. A large proportion of the lands which had been raised above the sea, being covered with fresh water, was best adapted for the abode of fluviatile and lacustrine quadrupeds.

Our knowledge of these quadrupeds is derived solely from their fossil remains; and as these are found chiefly (but not exclusively)* in the fresh-water formations of the tertiary series, it is to them principally that our present attention will be directed.

*The remains of Palæotherium occur, though very rarely, in the Calcaire Grossier of Paris. The bones of other terrestrial mammalia, occur occasionally in the Miocene and Pliocene marine formations, e. g. in Touraine and in the Sub-apennines. These are derived from carcases which, during these respective periods, were drifted into estuaries and seas.

No remains of mammalia have yet been found in the Plastic clay formation next above the chalk; the admixture of freshwater and marine shells in this formation seems to indicate that it was deposited in an estuary. Beds of fresh-water shells are interposed more than once between the marine strata of the Caleaire Grossier, which are placed next above the plastic clay.

Mammalia of the Eocene Period.

In the first great fresh-water formation of the Eocene period, nearly fifty extinct species of mammalia have been discovered by Cuvier; the greater number of these belong to the following extinct genera, in the order Pachydermata,* viz. Palæotherium, Anoplotherium, Lophiodon, Anthracotherium, Cheropotamus, Adapis (see Plates 3 and 4). †

• Cuvier's order Pachydermata, i. e. animals having thick skins, includes three subdivisions of Herbivora, of which the Elephant, Rhinoceros, and Horse are respectively examples.

The place of the genus Palæotherium (see Plates 3 and 4) is intermediate between the rhinoceros, the horse, and tapir. Eleven or twelve species have already been discovered; some as large as a rhinoceros, others varying from the size of a horse to that of a hog. The bones of the nose show that, like the tapir, they had a short fleshy trunk. These animals probably lived and died upon the margins of the then existing lakes and rivers, and their dead carcases may have been drifted to the bottom in seasons of flood. Some perhaps retired into the water to die.

Anoplotherium.

Five species of Anoplotherium (see Plates 3, 4) have been found in the gypsum of the neighbourhood of Paris. The largest (A. Commune) being of the size of a dwarf ass, with a thick tail, equal in length to its body, and resembling that of an otter; its probable use was to assist the animal in swimming. Another (A. Medium) was of a size and form more nearly approaching the light and graceful character of the Gazelle; a third species was nearly of the size of a Hare.

The posterior molar teeth in the genus Anoplotherium resemble those of the rhinoceros; their feet are terminated by two large toes, like the ruminating animals, whilst the composition of their

The nearest approach among living animals to the form of these extinct aquatic quadrupeds, is found in the Tapirs that inhabit the warm - regions of South America, Malacca, and Sumatra, and in the Daman of Africa.

It is not easy to find a more eloquent and striking acknowledgment of the regularity and constancy of the systematic contrivances that pervade the animal remains of the fossil world, than is contained in Cuvier's Introduction to his account of the bones discovered in the gypsum

tarsus is like that of the camel. The place of this genus stands, in one respect, between the rhinoceros and the horse; and in another, between the hippopotamus, the hog, and the camel.

Lophiodon.

The Lophiodon is another lost genus, allied most nearly to the tapir and rhinoceros, and, in some respects, to the hippopotamus, and connected closely with the Palæotherium and Anoplotherium. Fifteen species of Lophiodon have been ascertained.

Anthracotherium.

The genus Anthracotherium was so called from its having been first discovered in the Tertiary coal, or Lignite of Cadibona in Liguria: it presents seven species, some of them approximating to the size and character of the hog; others approaching nearly to that of a hippopotamus.

Cheropotamus.

The Cheropotamus was an animal most nearly allied to the hogs; in some respects approaching the Babiroussa, and forming a link between the Anoplotherium and the Peccary.

Adapis.

The last of the extinct Pachydermata found in the gypsum quarries of Montmartre, is the Adapis. The form of this creature most nearly resembled that of a hedgehog, but it was three times the size of that animal: it seems to have formed a link connecting the Pachydermata with the Insectivorous Carnivora.