RED CRAG: red ferruginous shelly sand, 25 feet thick, but local and inconstant. About 90 per cent. of the numerous shells occurring in this deposit are existing species—10.7 per cent. being northern forms.
LENHAM BEDS: sands, &c., occupying 'pipes' or hollows in the chalk of the North Downs, some 600 feet above the sea.
ST ERTH BEDS: clays and gravels, near St Erth, Cornwall; many shells, about 40 per cent. being of extinct species.
WHITE OR CORALLINE CRAG: shelly sands and clays; fossils abundant; 84 per cent. of the shells are living species, and of these 5 per cent. are northern forms. Polyzoa (popularly called corals) are numerous, hence the name sometimes applied to this group.
On the Continent Pliocene marine deposits are met with in various countries, usually in maritime regions, as at Antwerp and in the west of France in the Cotentin, Morbihan, and Aquitaine. But it is in the Mediterranean basin that this system attains its greatest development. Thus, at various points along the foot of the Alps in North Italy Pliocene beds appear, and they likewise occur along both sides of the Apennines, forming the sub-Apennine formation; while in Sicily they attain a thickness of 2000 feet. In middle Europe the most important Pliocene strata are the fresh-water beds of the Mayence basin, and the fresh and brackish water beds of the Tertiary basin of Vienna. The calcareous tufas of France and Italy belonging to this system are notable for their plant-remains.
Life of the Period.—The flora of Pliocene times indicates a more temperate climate than that of the preceding Miocene. Many Miocene forms still lived in Europe, but the palms and other characteristic Miocene plants had disappeared. Ivy, platanus, liquidambar, various maples, many walnut trees, elms, hornbeams, magnolia, tulip-tree, Canary laurel, oleander, vine, glyptostrobus, sassafras, and others ranged from Tuscany to the heart of France—such plants as beech, poplar, lime, oak, sassafras, maples, bamboos, vines, &c. growing amongst the mountains of Cantal. The general character of the flora recalls the floras of distant regions—North America, the Canary Islands, eastern Asia, and Japan. The abundant evergreen plants of the period seem to have grown chiefly on the low grounds; at higher elevations pines and deciduous trees were the prevailing forms. The flora of the Norwich Crag shows that towards the close of the period the British area was clothed with a vegetation somewhat similar to that of the present. The molluscan fauna includes an increasing number of living species. In the lower groups of the system the general facies of the shells is southern, but in the upper groups the southern types decrease in importance and are gradually replaced by temperate and northern forms. Amongst land animals we find several survivors from earlier times, such as Dinotherium and Mastodon, with which co-existed many other pachyderms—elephants, rhinoceroses, hippopotamuses, and tapirs. Herbivorous quadrupeds also abounded—horses, giraffes, and various cervine and bovine forms. Carnivores (panthers, bears, wolves, &c.) were well represented, and apes and monkeys also formed a marked portion of the fauna. The Pliocene beds of Pikermi in Attica, and of India (Siwalik group), have yielded a large number of extinct and living types. At Pikermi occur the remains of many ruminants, amongst which are species of giraffe, Helladotherium, and various cervine and bovine forms, together with Mastodon, rhinoceros, Dinotherium, hyæna, and others. The Siwalik beds contain Hyænarctos, Machairodus, and other Miocene forms, and Sivatherium and Bramatherium, gigantic four-horned animals allied to antelopes. With these are associated many living genera, such as Felis, Hyæna, Canis, Bos, Bison, Capra, Ovis, &c. It may be noted that from the Pliocene of the Upper Missouri region of North America remains of an abundant mammalian fauna have also been obtained—a fauna which had a strikingly oriental aspect.
In Pliocene times the Mediterranean covered many tracts which are now dry land. The valley of the Po then formed a great arm of the sea which penetrated into the mountain-valleys of the Alps, while Italy and Sicily were largely submerged. Considerable tracts in the maritime districts of southern and western France were likewise under water. The sea also overflowed some part of the south of England (Cornwall and Kent) and encroached upon the low grounds of Belgium and East Anglia. The long arms of the sea, which in the Miocene period had stretched from the Mediterranean through France into Switzerland and the valley of the Rhine, had vanished, while fresh-water and saline lakes occupied part of the area in Austro-Hungary which had been more or less open sea in Miocene times. Much of south-eastern Europe, however, continued submerged—the sea extending through the Aralo-Caspian depression into Asia. One of the most notable events of the Pliocene was the birth of Etna, Vesuvius, and the now extinct volcanoes of Central Italy. In early Pliocene times the climate was mild and genial, but the conditions became less so during the closing stages of the period. This change is evidenced particularly by the increasing number of northern molluscs and the occurrence of ice-floated erratics in the English Pliocene.