[AH] As for instance that of the Giant’s Causeway, Antrim.
FORAMINIFERAL ROCK-BUILDERS.
A. Nummulites lævigata—Eocene.
B. The same, showing chambered interior.
C. Milioline limestone, magnified—Eocene, Paris.
D. Hard Chalk, section magnified—Cretaceous.
This fact leads us naturally to consider in the second place the mammalia, and other land animals of the Tertiary. At the beginning of the period we meet with that higher group of mammals, not pouched, which now prevails. Among the oldest of these Tertiary beasts are Coryphodon, an animal related to the Modern Tapirs, and Arctocyon, a creature related to the bears and racoons. These animals represent respectively the Pachyderms, or thick-skinned mammals, and the ordinary Carnivora. Contemporary with or shortly succeeding these, were species representing the Rodents, or gnawing animals, and many other creatures of the group Pachydermata, allied to the Modern Tapirs and Hogs, as well as several additional carnivorous quadrupeds. Thus at the very beginning of the Tertiary period we enter on the age of mammals, It may be well, however, to take these animals somewhat in chronological order.
If the old Egyptian, by quarrying the nummulite limestone, bore unconscious testimony to the recent origin of man (whose remains are wholly absent from the Tertiary deposits), so did the ancient Britons and Gauls, when they laid the first rude foundations of future capitals on the banks of the Thames and of the Seine. Both cities lie in basins of Eocene Tertiary, occupying hollows in the chalk. Under London there is principally a thick bed of clay, the “London clay” attaining a thickness of five hundred feet. This bed is obviously marine, containing numerous species of sea shells; but it must have been deposited near land, as it also holds many fossil fruits and other remains of plants to which we shall refer in the sequel, and the bones of several species of large animals. Among these the old reptiles of the Mesozoic are represented by the vertebrae of a supposed “sea snake” (Palæophis) thirteen feet long, and species of crocodile allied both to the alligators and the gavials. But besides these there are bones of several animals allied to the hog and tapir, and also a species of opossum, These remains must be drift carcases from neighbouring shores, and they show first the elevation of the old deep-sea bottom represented by the chalk, so that part of it became dry land; next, the peopling of that land by tribes of animals and plants unknown to the Mesozoic; and lastly, that a warm climate must have existed, enabling England at this time to support many types of animals and plants now proper to intertropical regions. As Lyell well remarks, it is most interesting to observe that these beds belong to the beginning of the Tertiary, that they are older than those great nummulite limestones to which we have referred, and that they are older than the principal mountain chains of Europe and Asia. They show that no sooner was the Cretaceous sea dried from off the new land, than there were abundance of animals and plants ready to occupy it, and these not the survivors of the flora and fauna of the Wealden, but a new creation. The mention of the deposit last named places this in a striking light. We have seen that the Wealden beds, under the chalk, represent a Mesozoic estuary, and in it we have the remains of the animals and plants of the land that then was. The great Cretaceous subsidence intervened, and in the London clay we have an estuary of the Eocene. But if we pass through the galleries of a museum where these formations are represented, though we know that both existed in the same locality under a warm climate, we see that they belong to two different worlds, the one to that of the Dinosaurs, the Ammonites, the Cycads, and the minute Marsupials of the Mesozoic, the other to that of the Pachyderms, the Palms, and the Nautili of the Tertiary.
The London clay is lower Eocene; but in the beds of the Isle of Wight and neighbouring parts of the South of England, we have the middle and upper members of the series. They are not, however, so largely developed as in the Paris basin, where, resting on the equivalent of the London clay, we have a thick marine limestone, the Calcaire Grossier, abounding in marine remains, and in some beds composed of shells of foraminifera. The sea in which this limestone was deposited, a portion no doubt of the great Atlantic area of the period, became shallow, so that beds of sand succeeded those of limestone, and finally it was dried up into lake basins, in which gypsum, magnesian sediments, and siliceous limestone were deposited. These lakes or ponds must at some period have resembled the American “salt-licks,” and were no doubt resorted to by animals from all the surrounding country in search of the saline mud and water which they afforded. Hence in some marly beds intervening between the layers of gypsum, numerous footprints occur, exactly like those already noticed in the Trias. Had there been a Nimrod in those days to watch with bow or boomerang by the muddy shore, he would have seen herds of heavy short-legged and three-hoofed monsters (Palæotherium), with large heads and long snouts, probably scantily covered with sleek hair, and closely resembling the Modern Tapirs of South America and India, laboriously wading through the mud, and grunting with indolent delight as they rolled themselves in the cool saline slime. Others more light and graceful, combining some features of the antelope with those of the Tapir (Anoplotherium) ran in herds over the drier ridges, or sometimes timidly approached the treacherous clay, tempted by the saline waters. Other creatures representing the Modern Damans or Conies—“feeble folk” which, with the aspect of hares, have the structure of Pachyderms—were also present. Creatures of these types constituted the great majority of the animals of the Parisian Eocene lakes; but there were also Carnivorous animals allied to the hyæna, the wolf, and the opossum, which prowled along the shores by night to seize unwary wanderers, or to prey on the carcases of animals mired in the sloughs. Wading birds equal in size to the ostrich also stalked through the shallows, and tortoises crawled over the mud.
Lyell mentions the discovery of some bones of one of these gigantic birds (Gastornis) in a bed of the rolled chalk flints which form the base of the Paris series, resting immediately on the chalk; one of the first inhabitants perhaps to people some island of chalk just emerged from the waters, and under which lay the bones of the mighty Dinosaurs, and in which were embedded those of sea birds that had ranged, like the albatross and petrel, over the wide expanse of the Cretaceous ocean. These waders, however, like the tortoises and crocodiles and small marsupial mammals, form a link of connection in type at least between the Eocene and the Cretaceous, for bones of wading birds have been found in the Greensands indicating their existence before the close of the Mesozoic.
The researches of Baron Cuvier in the bones collected in the quarries of Montmartre were regarded as an astonishing triumph of comparative anatomy; and familiar as we now are with similar and yet more difficult achievements, we can yet afford to regard with admiration the work of the great French naturalist as it is recorded in its collected form in his “Recherches sur les Ossemens Fossiles,” published in 1812. His clear and philosophical views as to the plan perceptible in nature, his admirable powers of classification, his acute perception of the correlation of parts in animals, his nice discrimination of the resemblances and differences of fossil and recent structures, and of the uses of these,—all mark him as one of the greatest minds ever devoted to the study of natural science. It is obvious, that had his intellect been occupied by the evolutionist metaphysics which pass for natural science with too many in our day, he would have effected comparatively little; and instead of the magnificent museum in the “Règne Animal” and the “Ossemens Fossiles,” we might have had wearisome speculations on the derivation of species. It is reason for profound thankfulness that it was not so; and also that so many great observers and thinkers of our day, like Sedgwick, Murchison, Lyell, Owen, Dana, and Agassiz, have been allowed to work out their researches almost to completion before the advent of those poisoned streams and mephitic vapours which threaten the intellectual obscuration of those who should be their successors.