varied in some respects than it is now in any part of Europe, wood-beetles being especially numerous and large. In the thick underwood, frogs, toads, lizards, and snakes found their food. Through the forests there roamed antelopes, deer, and three-toed horses, while opossums, apes, and monkeys (Pliopithecus, Dryopithecus, Oreopithecus) gamboled among the branches. cats, bears (Hyænarctos), and sabre-toothed lions (Machairodus) were among the prominent carnivores of the time. But the most striking denizens of these scenes were undoubtedly the huge proboscidian creatures among which the Mastodon and Deino Wild FIG. 199.-Mastodon augustidens (). therium took the lead. The mastodon (Fig. 199) was a large and long-extinct form of elephant, which, besides tusks in the upper jaw, had often also a pair in the lower jaw. The deinotherium (Fig. 200) possessed two large tusks in the lower jaw which were curved downwards. This huge animal probably frequented the rivers of the time, using its powerful curved tusks to dig up roots, and perhaps to moor itself to the banks. Contemporaneous with these colossal pachyderms were species of rhinoceros, hippopotamus, and tapir. The rivers were haunted by crocodiles, turtles, beavers, and otters; while the seas were tenanted by ancestors of our living morse, sea-calf, dolphin, and lamantin. It is strange to reflect that such an assemblage of animals should once have found a home all over Europe. The deposits referable to the Miocene period in Europe indicate a great change in the geography of the region since Eocene and Oligocene times. While most of the Continent remained land, with large lakes scattered over its surface, certain tracts had subsided beneath shallow seas which penetrated here and there by long arms into the very heart of the region. Britain continued to be a land surface, and as such was continuously exposed to denudation. Instead of the formation of new deposits, there was an uninterruped waste of those already existing. So vast indeed has been the destruction of the Tertiary strata of Britain that it has evidently been in progress for an enormous period of time. Much of it, no doubt, took place during the long interval required elsewhere for the accumulation of the Miocene series of rocks. FIG. 200.-Skull of Deinotherium giganteum (reduced). Not only were the soft sands and clays of the older Tertiary groups of south-eastern England worn away from hundreds of square miles which they originally covered, but even the hard basalt-sheets of Antrim and the Inner Hebrides were so cut down by the various agents of denudation that wide and deep valleys were carved out of them, and hundreds of feet of solid rock were gradually removed from their surface. While Britain remained land, arms of the sea spread over what is now Belgium, and the basins of the Loire, Indre, and Cher, stretching across Southern France to the Mediterranean, passing along the northern base of the Alps, running into the valley of the Rhine as far north as Mainz, sweeping eastwards round the eastern end of the Alps, and expanding into the broad gulf of Vienna among the submerged heights of Austria and Hungary. The strata that tell this story of submergence contain an abundant assemblage of marine shells, many of which belong to genera that now live in warmer seas than those which at present bathe the coasts of Europe. Among them are Cancellaria, Cypræa, Mitra, Murex, Strombus, Arca, Cardita, Cytherea, Pectunculus, Spondylus, together with genera, such as Ostrea, Pecten, Cardium, Tapes, Tellina, which are familiar in the Northern seas. The district of France, formerly called Touraine, is largely overspread with shelly sands and marls, rarely more than 50 feet thick, and locally known as "Faluns." These deposits represent the floor of the shallow Miocene strait which extended across France. They have yielded upwards of 300 species of shells, the general character of which marks a warmer climate than now exists in Southern Europe. The tableland of Spain, with its northern mountainous border, rose along the southern margin of this strait which connected the Atlantic and the Mediterranean. Through this broad passage the large cetaceans of the time passed freely from sea to sea, for their bones are found in the upraised sea-bottom. The carcases of the mammals that then lived among the Pyrenees—mastodons, rhinoceroses, lions, giraffes, deer, apes, and monkeys-were likewise swept down into the sea. The deposits of the shallow Miocene straits and bays thus supply us with evidence of the position of the land and the character of its inhabitants. Eastwards the sea appears to have deepened over the region now occupied by the gulf of Genoa and the encircling mountain ranges, for the Miocene deposits of that part of the basin of the Mediterranean, consisting almost wholly of blue marls, are said to reach the great thickness of more than 10,000 feet. Beyond that depression the sea once more shallowed across the site of South-Eastern Europe. In the Vienna basin its deposits are well developed and consist of two divisions: (1) a lower group (Mediterranean or marine stage) of limestones, marls, clays, and sands, containing an abundant assemblage of shells, some of which belong to species still living in the present Mediterranean Sea, or off the west coast of Africa, and also numerous remains of land-plants which again recall the living floras of India and Australia; and (2) an upper group (Sarmatian or Cerithium stage) of sands, gravels, and clays in which the shells and terrestrial plants point to a much more temperate climate than that indicated by the lower beds. On the northern side of the Swiss Alps, the lake which was formed by the uplifting of the Eocene sea-floor, and in which so thick a succession of Oligocene strata was laid down, eventually disappeared among the terrestrial movements that submerged so much of Europe beneath the Miocene sea. Marine bands containing undoubted Miocene shells extend across Switzerland: but among them there are such abundant remains of terrestrial vegetation as to show that the land was not far off. No doubt the Alps, not yet uplifted to their ultimate height, rose along the southern borders of the strait that ran across Central Europe, and bore on their slopes luxuriant forest-growths. In Switzerland, however, we learn that before the close of the Miocene period the sea was once more excluded from the district, and another lake made its appearance. The marls, limestones, and sandstones accumulated in this lake (Eningen Beds) are among the most interesting geological deposits in Europe, from the great number and perfect preservation of the plants, insects, fishes, and mammals which have been obtained from them. A large part of our knowledge regarding the terrestrial vegetation and animal life of the Miocene period has been derived from these strata. Passing beyond the European area, we find that some of the characteristic vegetation of Miocene time spread northwards far within the Arctic Circle. In Spitzbergen and in North Greenland, an abundant series of plant-remains has been discovered, including a good many which occur also as fossils in the Miocene deposits of Central Europe. More than half of them are trees, among which are thirty species of conifers, also beeches, oaks, planes, poplars, maples, walnuts, limes, and magnolias. This flora has been traced as far as 81° 45′ north latitude, where the last expedition sent out from England found a seam of coal 25 to 30 feet thick, covered with black shales full of plant-remains. Miocene deposits occupy a considerable area in North America. In the Eastern States, they are of marine origin and follow generally the tract of the underlying Eocene beds. In the Western States and Territories they are lacustrine, and show that the lakes which covered so wide an expanse in early Tertiary time still existed, but in greatly diminished proportions. They have preserved many interesting relics of the terrestrial life of the period-three-toed horses, tapiroid animals, hogs as large as rhinoceroses, true rhinoceroses, huge elephant-like creatures allied to deinoceras and tapir, stags, camels, beavers, wolves, bears, and lions. In India, also, thick masses of sedimentary rock occur containing remains of mastodon, deinotherium, and other Miocene animals. PLIOCENE The last division of the Tertiary series of formations lays before us the history of the geological changes that brought about the present general distribution of land and sea, and completed the existing framework of the continents. Contrasted with the previous Tertiary groups, it is, on the whole, insignificant in thickness and extent, and it probably records the passing of a much less period of time, during which the amount of terrestrial revolution was comparatively trifling. Only in the basin of the Mediterranean are there any European Pliocene strata worthy of note on account of their thickness. The floor of that sea slowly subsided until sands, clays, and accumulated shell-beds had been piled up to a depth of several thousand feet. An important volcanic episode then took place. Etna, Vesuvius, and the other volcanoes of Central Italy began their eruptions. Thick masses of Pliocene sediments were ridged up on both sides of the Apennines, and in Sicily were upheaved to a height of nearly 4000 feet above the present sea-level. This elevation of the Pliocene sea-bed in the Mediterranean area was not improbably connected with other movements within the European region. The shallow firths and bays which still indented the Continent were finally raised into dry land, and the Alps may then have received their final uplift. While the European Pliocene deposits have their maximum thickness in the Mediterranean basin, they elsewhere represent the sediments of shallow seas and of lakes and rivers. The flora of the Pliocene period affords evidence of the continued advance of a more temperate climate. The tropical types of vegetation one by one retreated southwards in the European region, leaving behind them a vegetation that partook of the characters of those of the present Canary Islands, of North America, and of Eastern Asia and Japan, but which, as time wore on, approached more and more to the present European flora (Fig. 201). It included species of bamboo, sarsaparilla (Smilax), glyptostrobus, taxodium, sequoia, magnolia, tulip tree (Liriodendron), maple (Acer), buckthorn (Rhamnus), sumach (Rhus), plum (Prunus), laurel (Laurus), cinnamon-tree (Cinnamomum), sassafras, fig (Ficus), elm (Ulmus), willow (Salix), poplar (Populus), alder (Alnus), birch (Betula), liquidambar, oak (Quercus), evergreen oak (Quercus ilex), plane (Platanus), walnut (Juglans), hickory (Carya), and other now familiar trees. |