The Miocene is, for our special study, the most valuable and instructive of the Tertiary periods, both on account of its superior richness, and because we here meet with many types now confined to separate regions. Such facts as the occurrence in Europe during this period of hippopotami, tapirs, giraffes, Tragulidæ, Edentata, and Marsupials--will assist us in solving many of the problems we shall meet with in reviewing the actual distribution of living forms of those groups. Still more light will, however, be thrown on the subject by the fossil forms of the American continent, which we will now proceed to examine. {129}CHAPTER VII. EXTINCT MAMMALIA OF THE NEW WORLD. The discoveries of very rich deposits of mammalian remains in various parts of the United States have thrown great light on the relations of the faunas of very distant regions. North America now makes a near approach to Europe in the number and variety of its extinct mammalia, and in no part of the world have such perfect specimens been discovered. In what are called the "Mauvaises terres" of Nebraska (the dried-up mud of an ancient lake), thousands of entire crania and some almost entire skeletons of ancient animals have been found, their teeth absolutely perfect, and altogether more resembling the preparations of the anatomist, than time-worn fossils such as we are accustomed to see in the museums of Europe. Other deposits have been discovered in Oregon, California, Virginia, South Carolina, Texas, and Utah, ranging over all the Tertiary epochs, from Post-Pliocene to Eocene, and furnishing a remarkable picture of the numerous strange mammalia which inhabited the ancient North American continent. NORTH AMERICA--POST-PLIOCENE PERIOD. _Insectivora._--The only indications of this order yet discovered, consists of a single tooth of some insectivorous animal found in Illinois, but which cannot be referred to any known group. _Carnivora._--These are fairly represented. Two species of _Felis_ as large as a lion; the equally large extinct _Trucifelis_, found only in Texas; four species of _Canis_, some of them larger {130}than wolves; two species of _Galera_, a genus now confined to the Neotropical region; two bears, and an extinct genus, _Arctodus_; an extinct species of racoon (_Procyon_), and an allied extinct genus, _Myxophagus_--show, that at a very recent period North America was better supplied with Carnivora than it is now. Remains of the walrus (_Trichechus_) have also been found as far south as Virginia. _Cetacea._--Three species of dolphins belonging to existing genera, have been found in the Eastern States; and two species of _Manatus_, or sea-cow, in Florida and South Carolina.