The Pliocene mammalian land fauna lived at a period when Europe had already obtained the main features of its present configuration. Italy, to be sure, at the beginning of this period was still partly overflowed by the sea, and in Belgium, Holland, and the South of England, the North Sea extended further over the land than to-day and left behind the deposits known as the Crag. Over the extended mainland of Central Europe, the conditions for the preservation of mammals were, on account of the absence of more extended fresh-water lakes, extremely unfavourable. Only the volcanic tuffs in Auvergne, the fissures filled with Bohnerz of the Upper Rhone valley, and the scattered fresh-water deposits of the Rhone valley, Roussillon and the neighbourhood of Montpellier, contain remains of the Pliocene land fauna, which are handed down in greater perfection in the swampy, and in part coal-bearing, sediments of the Arno valley and in the partly marine formations of Piedmont and the Romagna.