of these animals also indicate a lacustrine, or swampy condition of the regions they inhabited: one of them, the Dinotherium giganteum (gigantic Tapir of Cuvier), is calculated to have been eighteen feet in length, and was much the largest of all terrestrial Mammalia yet discovered, exceeding even the largest fossil elephant.
The Dinotherium will be described in a subsequent chapter.
Mammalia of the Pliocene Periods.
The third, and fourth, or Pliocene divisions of the tertiary fresh-water deposites, contain no more traces of the extinct lacustrine genera of the Palæotherian family, but abound in extinct species of existing genera of Pachydermata, e. g. Elephant, Rhinoceros, Hippopotamus, and Horse, together with the extinct genus Mastodon. With these also occur the first abundant traces of Rurninantia, e. g. Oxen and Deer. The number of Rodentia becomes also enlarged; and the Carnivora assume a numerical importance commensurate with the increased numbers of terrestrial herbivore.
The seas, also, of the Miocene and Pliocene periods, were inhabited by marine Mammalia, consisting of Whales, Dolphins, Seals, Walrus, and the Lamantin, or Manati, whose existing species are chiefly found near the coasts and mouths of rivers in the torrid zone (see Pl. 1. Figs. 91 to 101). The presence of the Lamantin adds another argument to those which arise from the tropical character of many other animals, even of the latest tertiary strata, in favour of the opinion, that the climate of Europe maintained a high, though probably a gradually decreasing temperature, even to the latest periods of tertiary formations.
We have many sources of evidence whereby the history of the Pliocene periods is illustrated: First, we have the remains of terrestrial animals, drifted into estuaries or seas,
