The fresh-water lakes, around which these various animals have lived, and which had received their bones, nourished, besides the tortoises and crocodiles, some fishes and testaceous mollusca. All that have been collected of these two classes of animals, are as foreign to our climate, and even as much unknown in our present waters, as the palæotheria, and other quadrupeds which were coeval with them[293]. The fishes have even in part belonged to unknown genera. Hence, it cannot be doubted that this race of inhabitants, which might be termed the population of the middle age, this first great production of mammifera, has been entirely destroyed; and, in fact, in all places where remains of them have been discovered, there are great deposits of marine formation above them, so that the sea has overwhelmed the countries which these races inhabited, and has rested upon them during a long period of time. Have the countries inundated by it at this period been of great extent? This is a question which the examination of those ancient deposits formed in their lakes do not enable us to answer. To this period I refer the gypsum beds of Paris and those of Aix, several quarries of marly stones, and the molasse sandstones, at least those of the south of France. I am of opinion that we should also refer to it the portions of the molasse sandstones of Switzerland, and of the lignites of Liguria and Alsace, in which quadrupeds are found of the families enumerated above; but I do not find that any of these animals have been also found in other countries. The fossil bones of Germany, England, and Italy, are all either older or newer than those of which we have been speaking, and belong either to those ancient races of reptiles of the juraic and copper-slate formations, or to the deposits of the last universal inundation, the diluvial formations. We are, therefore, authorised to believe, until the contrary be proved, that at the period when these numerous pachydermata lived, the globe had only presented for their habitation a small number of plains sufficiently fertile for them to multiply there, and that perhaps these plains were insulated regions, separated by pretty large spaces of elevated chains, in which we do not find that our animals have left any traces of their existence. The researches of M. Adolphe Brongniart have also made known to us the nature of the vegetables which covered those countries. In the same strata with our palæotheria, there have been found trunks of palms, and many others of those beautiful plants whose genera now only grow in warm climates. Palms, crocodiles, and trionyces always occur in greater or less abundance wherever our ancient pachydermata are found[294].