MAMMALIA OF PLIOCENE PERIODS. 79 



of these animals also indicate a lacustrine or swampy con- 

 dition of the regions they inhabited : one of them, the Dino- 

 therium 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, exceed- 

 ing even the largest fossil elephant. 



The Dinotherium will be described in a subsequent chap- 

 ter. 



Mammalia of the Pliocene Periods. 



The third, and fourth, or Pliocene devisions of the tertiary 

 fresh-water deposites, contain no more traces of the extinct 

 lacustrine genera of the Palaeotherian 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 Ruminantia, e. g. Oxen and 

 Deer. The number of Rodentia becomes also enlarged; 

 and the carnivora assume a numerical importance com- 

 mensurate with the increased numbers of terrestrial herbi- 

 vora. 



The seas, also, of the Miocene and Pliocene periods, were 

 inhabited by marine Mammalia, consisting of Whales, Dol- 

 phins, 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 PI. 1, Figs. 97 to 101.) The 

 presence of the Lamantin adds another argument to those 

 which arise from the tropical character of many other ani- 

 mals, even of the latest tertiary strata, in favour of the opi- 

 nion, 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 re- 

 mains of terrestrial animals, drifted into estuaries or seas. 



