« AnteriorContinuar »
interesting zoological facts developed, although on the whole the natural history of the period in question manifestly combines the more ancient character of the older strata with the recent zoology and botany of the same countries at present. Without at all dwelling on the subject of the fossil shells and other Invertebrata of the period, a group of some characteristic forms is given to mark the gradual and peculiar approximation to the existing fauna.
In beds of the middle or newer part of the tertiary epoch, there are also occasionally found numerous remains of reptiles, but these are chiefly confined to forms more or less resembling those of existing nature. Amongst them, however, may be mentioned a gigantic salamander, once thought to be the remains of some human skeleton, and numerous turtles and tortoises exhibiting marked peculiarities of structure. The beds at Oeningen, in Switzerland, near to the Lake of Constance, offer a rich variety of such forms, and include, also, many very interesting species
* 125, Venus. 126, Pecten. 127, Auricula. 128, Turritella. 129, Mitra. 130, Conus.
of fishes, all of which are extinct. The figure annexed (131) represents an interesting chelonian animal from this district.
OENINGEN FRESH-WATER TORTOISE.
Of the quadrupeds of this middle period, the Dinotherium* is in some respects the most remarkable, not only in point of size, but in its relation to the anoplotheroid animals of the older beds on the one hand, and to the elephantine animals of more recent times on the other. The remains of this monster are nowhere common, but have been found both in the Middle Rhine valley (between Mayence and Bâle), and also in the valleys of the Jura chain.
It dwelt, probably, in swamps. Its length was nearly twenty feet; its body, huge and barrel-shaped, very much resembling that of the hippopotamus, being little raised above the ground, although the huge columns which formed its legs are supposed to have been nearly ten feet in length. Its head, rarely,
* Aɛivos (deinos), fearfully large; Onpiov (therion), a beast.
perhaps, brought entirely above the water, was like that of a large elephant, and it was provided with a short, but very muscular and powerful proboscis. A pair of large and long tusks were appended to this skull, and curve downwards, as in the
walrus. But observe the fact most remarkable of all. These tusks do not proceed from the upper jaw, whence they could be made to depend entirely upon the bones of the neck to support them, but are fixed in the lower jaw, and are planted, as it would seem, in this strange position at the greatest posThere can scarcely
sible mechanical disadvantage. be a doubt that an animal provided with appendages so placed was an inhabitant of water; and the tusks, which are very large, were probably useful as pickaxes, enabling the monster to dig for succulent vegetable food by day, while perhaps at night they could be attached like anchors to the banks of the river or lake in which the animal habitually dwelt. It was the most gigantic of the herbivorous quadrupeds, and was associated with the palæotheres of the more ancient tertiary period, and with the mastodons and elephants which lived on till a far more recent date.
It is not unlikely that at this time, when the palæotherium and the dinotherium were thus companions of the elephant, a large fresh-water lake covered what is now the valley of the Middle Rhine. This supposition involves the existence of tracts of land enclosing such lake, but the direction of the land must have been somewhat different from that now adjacent. An open sea then seems to have extended from the Caspian and Black Seas towards the northwest, quite into the north of Switzerland. The present chain of the Alps was rising and assuming the character of a mountain range, forming, perhaps, islands in this great sea, which must have covered the whole of Italy, Turkey, and Greece, a great part of Asia Minor, and much of northern Africa. The great features of the modern fauna, and even of the flora of these districts, were, however, already in the course of development; the continent of Europe was beginning to assume its general contour; England was, perhaps, already an island, though in that case only recently separated from the main land, to which it was afterwards united; and the pent-up gases, whose efforts to escape were lifting extensive districts above the sea-level, and forming great chains of mountains in north Italy, were partly and at intervals relieved by volcanic eruptions which took place in central France, in north-eastern Spain, and in the Lower Rhine, near the present town of Bonn. Possibly it was also at this time (though the event may have occurred earlier) that the great submarine flow of melted rock took place, whose effects are seen in the north-east of Ireland and the opposite islands of Scotland, where the chalk is covered by this erupted
matter. The picturesque basaltic columns of the Giant's Causeway and Staffa mark the extent and intensity of a line of volcanic action, which has long ceased to produce direct results in the British islands. After the lapse of a certain period, and when the elevatory movements had long gone on, the continent of Europe was at length fully brought above the surface of the sea, and became a fit habitation for the land animals of various kinds gradually introduced upon it. The deep and broad inlets of the sea became valleys and plains; the lakes were drained by the great river channels, which, owing to the greater elevation of the interior, conveyed the water in a definite and short course to the sea, instead of allowing it to stagnate over wide tracts of low swampy land; and the whole Continent put on its present aspect.
But during these changes the climate had also become greatly modified. The increased proportion of land, especially towards the north, would necessarily lower the general temperature, and at the same time render the climate more excessive. Vast forests, composed of oak and beech and other modern trees, produced other and not unimportant modifications; and at this period, probably before the great expanse of land towards the North Pole had arisen from the sea, and while the general character of the great European tract was still insular, vegetation extended almost to the Arctic Circle, and to such an extent as to provide food and shelter for the largest quadrupeds. This combination of analogies and differences forms throughout a somewhat striking character of the middle period, and we find, as one result, that the physiognomy of the fauna at pre