This classification has the inconvenience of being purely local, since the disappearance of quaternary species did not take place everywhere at the same time, and was not general. In reality the age of the reindeer still continues in Lapland, and that of the aurochs is prolonged, a little artificially it is true, in the forests of Lithuania. But Lartet’s method connects human groups with animal types; it characterises the epochs by an event palæontologically important; it preserves the relation between the succession of periods and biological events; it offers, therefore, serious advantages if taken for what it is. This was very clearly understood by the eminent author of the theory; he has only applied it to France. Since M. Lartet made his splendid investigations, fresh facts have come to light, and, as it often happens, distinctions, which at first were apparently most pronounced, have now been partly effaced. Therefore M. Dupont has proposed to reduce to two the four ages of Lartet, which is perhaps excessive even for Belgium. M. Hamy, again, has admitted three ages as corresponding to the mean and new river levels of M. Belgrand. This division of quaternary times has the advantage of being connected with geological phenomena; it at least partly loses the too exclusively local character, and it ought for this reason to be preferred. Let us, nevertheless, consider the subject for a moment from Lartet’s point of view, which permits of an interesting comparison. We have seen in Denmark the succession of three vegetable species; the beech, the oak, and the pine bring us to the commencement of the present modern epoch. In France the successive disappearance of four animal species, the cave-bear, mammoth, reindeer, and aurochs, which at first were contemporaneous on our soil, characterises so many epochs which embrace the whole quaternary period. Man has been contemporaneous with them all; he made use of their flesh for food, and has left representations of them in sculpture and drawings. VI. Can we go further and find traces of man even in tertiary times? Falconer, the celebrated English palæontologist, prematurely lost to science, did not hesitate to reply in the affirmative. But he only expected to find tertiary man in India, and M. Desnoyers has discovered him in France. It was in 1863, in the gravel-pit of Saint-Prest, near Chartres, that M. Desnoyers himself found a tibia of rhinoceros bearing marks of incision and grooves similar to those which had been so often noticed in the bones of bears and reindeer eaten by quaternary man. A careful comparison and numerous facts of the same nature, shown in different collections, authorised him to announce that man might be traced beyond the glacial epoch, and had lived in pliocene times.