PLIOCENE (Gr. more recent), the name given by sir Charles Lyell to a section of the upper tertiaries, because the organic remains found in it contain between 60 and 70 per cent of living species; a greater proportion than exists iu the older ntiocene, but not so' great as that found in the succeeding pleistocene.
The beds belonging to this period are very local. They have been noticed in several,. places in Europe, bat have been chiefly studied in Suffolk. the only locality in which. they occur in Brrtain. Here they cover the upper beds of the London clay; and being composed of shay sand, they have, like similar deposits, been used for fertilizing lands, deficient in calcareous matter, and have received the local name of "crag." They are divided into the (1) red crag, 50 ft. ; (2) continue crag, 50 ft.
The red crag consists of beds of (outmost; sands and gravel with a mixture of shells, for the most part rolled, and sometimes broken up into sand. The ‘vhole deposit, with the contained fossils, has a deep ferruginous or ocherous color. It seems to have been formed in shallow water, the currents of which have given it a very variable character, and frequently confused the stratification, as in some modern sandbanks. The fossils have a somewhat boreal character. They consist chiefly of mollusea; but there have been also found the bones and teeth of large sharks, skates, and other fish, and the ear bones of one or more true whales.
The continue erag is generally calcareous and marly, consisting of a mass of shells and polyzoa, separated in some places by thin layers of hard limestone, and coral-like Masses, which occupy the position in which they lived. It is easily separated front the red crag by its white color. It has been foamed at a greater depth and in more tranquil
water than the newer deposit. The fossils have a more southern facies than those of the red crag, and indicate that they lived in an ocean with a higher temperature. Among these southern forms may be mentionedspecies of the genera conus, oliva, mitra, voluta, aitd pyrula. The calcareous polyzoa are abundant and very beautiful; and several inter esting forms of echini have been described. A few fossils of the same species as those occurring in the London clay have been found in this and the red crag, but these are Lelieveu to have peen washed out of the inferior deposits.
Mr. Searles Wood has obtained 345 species of testacca from the coralline crag, and 230 from the red crag, of which about 150 are common to both; about 70 per cent of the newer division are also recent, and about GO per cent of the older.
Pliocene deposits have been observed in the neighborhood of Antwerp and on the batiks of the Scheldt, from which 200 species of shells have been obtained, two-thirds of which were already known from Suffolk. More than a half are recent species found in the northern seas, mid a few are still living in the Mediterranean. Similar deposits occur itt Normandy. The low bills between the Apennines and the sea on each side of Italy are formed to a considerable extent of beds belonging to this period; and the marine strata of the seven hills of Rome are of the same age. Beds of a brackish-water origin, observed on the shores of the Caspian, Aral, Azof, and Black seas, have been referred to this period.