Yet

of famine as food; for which it is not entirely unsuitable, seeing that there is always a small percentage of animal matter left in it, in addition to the siliceous shields. So extremely small are the creatures of which these rocks form the sepulchre, that, according to M. Ehrenberg's calculation, ten millions of millions of individuals might be required to fill the space of a cubic inch. in the smallest of such creatures, there have been found several stomachs, besides other organs; and minute as the coverings necessarily are, they are found variously sculptured or marked, so as to form distinctions of species. These circumstances certainly afford a curious view not only of the wondrous power of the Creator, but of the surprising extent to which His most interesting production, the human mind, has been fitted to go in research, by aid of instruments, the powers of which are also of His institution.

The other invertebrate animals of the Tertiary are not remarkable, except for their making a gradual approach to the appearance of those which now exist. The corals are generally of small size; the echinodermata are rare, compared with their abundance in earlier rocks; the crustaceans are not numerous; but insects begin to be found in abundance. The mollusca are extremely numerous in species; but the cephalopoda of the early seas seem to have now in a great measure given place to an order of meaner organisation (gasteropoda), which become much more varied in form than in the older rocks. Of fishes there are abundance of species; but reptiles, so conspicuous in the two preceding formations, are not now prominent. The great saurians or fish-lizards are extinct, and are not replaced by any similar families. At the commencement of the Tertiaries, three_orders of reptiles existed-Chelonia (tortoises), Crocodilia, and Batrachia (frogs); another now existing, Ophidia (serpents), was, as far as research has yet gone, wanting. The earliest appearance of the serpent is in the remains of one of large size (probably eleven feet long, and resembling the boa constrictor), which have been found in the London clay of the Isle of Sheppey. It is such an animal as could only live in a tropical climate.

We have seen that the existence of birds and mammalia has been very slightly evidenced in the Secondary Formation, shewing at least that these creatures were in very small number in the ages represented by those strata. We are now to see both of these classes -the highest in the animal kingdom-enter in great force upon the field of existence. It seems as if a considerable interval had existed between the conclusion of the Chalk Formation and the beginning of the Tertiary, for these classes come upon us all at once in numerous species in the Eocene. In fresh-water strata of that portion of the Tertiary in the great Paris basin, M. Cuvier found remains of about fifty extinct species of mammalia, together with various examples of birds. The birds were of the genera represented by the buzzard, owl, quail, woodcock, curlew, and pelican; and to these has

been added, from the corresponding strata in the London basin, a species referred to the family of vultures.

THE GREAT PACHYDERMS.

The most remarkable of the animals found in the Paris basin are large Pachyderms, or thick-skinned animals, of a division now represented only by four species. By the discovery of these remains, naturalists were enabled to make up a comparatively complete series of a division of the earth's creatures, which had previously been remarkably imperfect. Two genera are particularly described by geologists, namely, Palæotheria and Anoplotheria, the former being intermediate in character between the tapir of South America and the rhinoceros, while the latter seems a link from the rhinoceros to the hippopotamus. The Great Palæotherium was an animal of the size of a horse, or about four feet and a half to the wither. It was

Form of Palæotherium.

more squat and clumsy in its proportions than the horse; the head was more massive, and the extremities thicker and shorter. On each foot were three large toes, rounded and unprovided with claws; and from the nose proceeded a short fleshy trunk. The Palæotherium probably lived, like the tapir of North America and Asia, in swampy districts, feeding, as its congeners still do, on coarse vegetable substances. The Anoplotheria, of which six species have been determined, were of various bulk, from a hare up to a dwarf ass. Two species were about eight feet long, including a tail of three feet. These animals seem also to have inhabited marshy places, repairing frequently to the water to feed upon roots and the leaves of aquatic succulents. Another species was light and graceful, like the gazelle, and probably, like that animal, fed upon aromatic herbs and the _young shoots of shrubs. Amongst the other animals found in the Eocene of the Paris basin, were species of the wolf and fox, and of the racoon and genette, of the opossum, dormouse, and squirrel; besides birds, reptiles, and fishes.

The second, or Miocene period of the Tertiary age, brings us a step nearer to the existing condition of things. A strong proof of this is derived from the shells of the strata of this period. Whereas only three in the hundred Eocene fossils were of recent species, of the Miocene shells we find eighteen in the hundred to have existing representatives. Along with the mammalia, also, of the Eocene period, we find that the Miocene deposits present us with the earliest forms of animals existing at the present time. In Dr

Buckland's Bridgewater Treatise a table is given, exhibiting the animals found at Darmstadt in a bed of sand referrible to the Miocene period. In this list are mentioned two skeletons of the dinotherium (represented in the vignette to this tract), a large herbivorous animal, called by Cuvier the Gigantic Tapir; two large tapirs; calicotherium, two large tapir-like animals of this name; two rhinoceroses; hippotherium, an animal allied to the horse; three hogs; four large cats, some as large as a tiger; the creature called the Glutton; agnotherium, allied to the dog; and machairodus, an animal allied to the bear. From this list the reader will perceive the gradual approach in the Miocene animals to existing species. The largest of the terrestrial mammalia yet discovered belongs to the period now under notice; it is the dinotherium, or gigantic tapir, already mentioned. No complete skeleton has yet been discovered; but from the bones found, Cuvier and others imagine the animal to have reached the extraordinary length of eighteen feet. The most remarkable peculiarities of its structure consist in two enormous tusks at the end of its lower jaw, and in the shoulder-blade, which resembles that of a mole, and is calculated to have given the power of digging, or other free movement, to the fore-foot. It seems probable that this stupendous creature lived in fresh-water lakes, and had the half-terrestrial half-aquatic habits of the walrus or riverhorse. The tusks might be used in digging up roots and plants, and also in sustaining the head on banks during sleep, or in pulling the body out of the water, as the walrus uses a similar pair of tusks. 'In these characters,' says Buckland, ‘of this gigantic, herbivorous, aquatic quadruped, we recognise adaptations to the lacustrine (lakecovered) condition of the earth, during that portion of the Tertiary periods to which the existence of these seemingly anomalous creatures seems to have been limited.'

In the Miocene period, the seas became the habitation of numbers of marine mammalia, consisting of dolphins, whales, seals, walrus, and the lamantin, or manati. Few of these animals were of the same species as those which exist at present, but the differences were far from being great or remarkable. This circumstance, as well as the considerable number of fossil shells identical with existing ones, exhibits an approach in the character and tenantry of the Miocene seas to the present state of things in these respects. The discovery, also, of true terrestrial mammalia, as the rhinoceros and hog, in the Miocene formations, shews that, since the era of the gigantic reptiles, no slight portion of the earth's surface had assumed the condition of dry land, fit for the support of the common herbivora.

THE MASTODON, MEGATHERIUM, ETC.

It now remains to inquire into the nature and peculiarities of the animals characterising the Pliocene age, which, for convenience, has

been arranged into two periods, the Older and Newer Pliocene, the latter of which immediately preceded the formation of the diluvial layer constituting the present superficial matter of the globe. Whereas only eighteen in the hundred of the Miocene shells were of recent species, in the Older Pliocene from thirty-five to fifty, and in the Newer Pliocene not less than from ninety to ninety-five in the hundred, are identical with shells of existing species. This great change is accompanied by the disappearance of the Palæotherian family and others, which formed the most striking animals in the periods immediately preceding. In place of these extinct species of extinct Pachydermatous or thick-skinned families, we observe in the strata of the Pliocene periods a vast number of remains of existing Pachydermatous families, such as the elephant, the rhinoceros, and the hippopotamus, though these remains belong to varieties that are now extinct. The first traces also now appear of Ruminant animals—of oxen, deer, camels, and other creatures of the same class.

The enormous creature called the Great Mastodon, belonging to the Pliocene era, was the largest of all the fossil animals whose skeletons have been found complete, or nearly so. Much confusion has existed relative to this animal's true character, many naturalists regarding it as an extinct species of the elephant, and others holding that it approached nearer to the hippopotamus. Cuvier, however, determined it to be the head of a distinct family, comprehending several other species. It is about one hundred and twenty years since remains of the mastodon were first discovered in America, and vast quantities of them have been since found in the same region, buried chiefly in marshy grounds. One skeleton, nearly complete, was dug up on the banks of the Hudson in 1801, and it is from this that a correct knowledge of the animal has been principally derived. In height, the mastodon seems to have been about twelve feet, a stature which the Indian elephant occasionally attains. But the body of the mastodon was greatly elongated in comparison with the elephant's, and its limbs were thicker. The whole arrangement of the bony structure resembled that of the elephant, excepting in one point, which Cuvier regarded as of sufficient consequence to constitute the mastodon a different genus. This was the cheek-teeth, which are divided, on their upper surface, into a number of rounded, obtuse prominences, arranged not like the elephant's but like those of the wild boar and hippopotamus; whence it is concluded, that, like the latter animals, the mastodon must have lived on tender vegetables, roots, and aquatic plants, and could not have been carnivorous. The lower jaw of a skeleton found on the Hudson is two feet ten inches in length, and weighs sixty-three pounds. Like the elephant, the mastodon had two tusks, curving upwards, and formed of ivory, and, in the opinion of Cuvier, it had also a trunk of the same kind with the former animal's.

Another creature, belonging to the later Pliocene ages, if not indeed

to the era of the Diluvial formation, has been discovered in America, both north and south. This is the Megatherium, an animal more widely removed in character from any existing creature, than any of the other fossil remains that have been yet observed. The megatherium was discovered towards the end of the last century. A skeleton, almost entire, was found nearly at one hundred feet of depth, in

excavations made on the banks of the river Luxan, several leagues to the south-west of Buenos Ayres. The megatherium was a tardigrade (slow-moving) animal, like the sloth, and was at least the size of a common ox. Its limbs were terminated by five thick toes, attached to a series of huge flat metatarsal bones, or those bones with which the toes are continuous as in the human foot. 'Some of the toes,' says Buckland, in his notice of this creature,' are terminated by large and powerful claws of great length; the bones supporting these