The only possible alternative to this evidence from Perrier would be to throw back the duration of the Quaternary and limit that of the Pliocene enormously, by supposing that all the deposits above the great glacial conglomerate or old moraine, are inter-glacial and not Tertiary. This is, as has been pointed out, very much a question of words, for the phenomena and the time required to account for them remain the same by whatever name we elect to call them. But it still has its importance, for it involves the fundamental principle of geology, that of classifying eras and formations by their fauna. If the _Elephas Meridionalis_ is a Pliocene and not a Quaternary species, we must admit, with the great majority of continental geologists, that the first and greatest glaciation fell within the Pliocene period. If, on the other hand, this elephant is, like the mammoth, part of the Quaternary fauna, we may believe, as many English geologists do, that the first glacial period coincided with and probably occasioned the change from Pliocene to Quaternary, and that everything above the oldest boulder-clays and moraines is not Tertiary but inter-glacial. As bones of the _Elephas Meridionalis_ have been frequently found in connection with human implements, and with cuts on them which could only have been made by flint knives ground by the human hand, it will be seen at once what an interest attaches to this apparently dry geological question, of the age of the great southern elephant. The transition from the mastodon into the elephant took place in the Old World (for in America the succession is different) in the Pliocene period. In the older Pliocene we have nothing but mastodons, in the newer nothing but elephants, and the transition from the older to the newer type is distinctly traced by intermediate forms in the fossil fauna of the Sewalek hills. The _Elephas Meridionalis_ is the oldest known form of true elephant, and it is characteristic of all the different formations of the Upper Pliocene, while it is nowhere found in cave or river deposits which belong unmistakably to the Quaternary. It was a gigantic animal, fully four feet higher than the tallest existing elephant, and bulky in proportion. It had a near relation in the _Elephas Antiquus_, which was of equal size, and different from it mainly in a more specialized structure of the molar teeth, and the remains of this elephant have been found in the lower strata of some of the oldest bone-caves and river-silts, as to which it is difficult to say whether they are older or younger than the first glacial period. The remains of a pygmy elephant, no bigger than an ass, have also been found in the Upper Pliocene, at Malta and Sicily, and those of the existing African elephant in Sicily and Spain. It would seem, therefore, that the Upper Pliocene was the golden age of the elephants where they were most widely diffused, and comprised most species and most varieties, both in the direction