Tertiary deposits are well developed in the interior of the United States between the Mis sissippi River and the Rocky Mountains. They consist of non-marine strata, partly lacustrine, partly eolian and partly made up of wash from the mountain sides tn the form of coarse alluvial cones or fans. In these deposits nu merous bones of extinct mammalia are found, of which extensive collections have been gath ered in the various museums of the country, particularly in the American Museum of Natu ral History in New York. Most of the deposits are in isolated basins, and can only be correlated by their vertebrate fauna. On the Pacific Coast, all the epochs of the Tertiary are represented, being in part marine, in part terrestrial.
Life of the Tertiary.—At the close of the Cretaceous period all the flying reptiles and dinosaurs, and most of the marine reptiles, seem to have become extinct ; and the Tertiary formations, so far as known, yield only forms of Vertebral° essentially similar to those of the present day. Among fishes, all of the ex isting suborders and many of the existing families or even genera seem to occur in the Eocene. Among the invertebrates, ammonites, belemnites and most of the crinoids had passed away when the Tertiary era began; and forms came in, whose descendants are now familiar to us. The Mammalia suddenly appeared as the
dominant type on all the continents and the evolution of many of the minor groups can be traced. Primitive tapirs and primitive horscs, with four toes (Orohippus and Eohippus) oc cur. Among the Oligocene mammals may be mentioned the Mesoluppus, or horse with only three functional toes. The peculiar Oreodon occurs in beds above the Titanotherium and represents. a type intermediate between hog and deer in structure. Early camels, the ear liest true carnivores, early bats, squirrels and rodents and marsupials also occur in these beds. MiohipPus, a still more modified horse, occurs in the John Day and the Deep River beds; in the latter also occurs the oldest mastodon. In the Loup Fork beds occur Procamelus, Mastodon and dogs of the genus Canis. Con suit Dana, 'Manual of Geology' (New York 1895); Zittell, (Textbook of Paleontology' (New York 1900-04); Cope, 'Vertebrata of the Tertiary Formations of the West' (Wash ington 1884) ; Williams, (Geological Biology' (New York 1895); Woodward, (Vertebrate PaIxontology) (London 1898, which contains an extensive bibliography). See CENOZOIC