the latter portion of the Tertiary period. They include a remarkable group of animals, belonging to the order Edentata, of which the sloth, the armadillo and the anteater are representatives in the fauna of the present day. The Megatherium (mega, great; therion, beast,) was a gigantic quadruped exhibiting some very striking resemFig. 151. The Megatherium. blances to the sloth. Its length is eighteen feet, its breadth across the loins six feet, while its height was nine feet. Its proportions were singularly massive, its pelvis and hind extremities being three times as large as those of the elephant. The fore legs were long, resembling in structure those of the sloth. The fore foot was a yard long, twelve inches broad, five-toed, and armed with long and powerful claws. This animal is taken as the type of the Megatheroid group. 276. The Mylodon (mule, a mill; odous, a tooth,) an allied genus found in the same locality, in some respects more closely resembles the sloth. Prof. Owen has given a full description of a perfect skeleton of this animal obtained from Buenos Ayres, and deduced its relations and habits. The length of the skeleton is eleven feet, inclu ding the tail. Its teeth show that it was a vegetable eater; it probably lived, as do the sloths of the present day, on leaves and buds of trees. Fig. 152. Mylodon Robustus. 277. The Megalonyx (megale, great; onux, claw,) resembled the mylodon in its size and proportions; it differed in its claws, and in greater freedom of motion in its fore limbs. The Scelidotherium (scelidos, the thigh; therion, beast,) though allied to the megatherium, resembled the ant-eater and armadillo. In its hinder extremities and tail, the strength was greater in proportion than in any known animal, living or extinct; while the length of the animal was not greater than that of a Newfoundland dog, and its fore limbs no larger, its hind extremities were as ponderous as those of the hippopotamus.* 278. Associated with the megatheroid animals of this period was a colossal armadillo, called the Glyptodon (gluptos, sculptured; odous, tooth,) from its teeth being sculptured laterally with wide, deep grooves. Like the armadillo it was covered with a crust or shell, composed of polygonal pieces accurately fitting each other, constituting a massive armour. The structure of its hind foot is very peculiar, presenting a frame work unparalleled in its adaptation to support a great weight, and at the same time allow such free motion in the fore limbs as the habits of the armadillo require. Several species of the genus glyptodon have been determined. The remains of the mastodon have been found in the same localities with the megatheroid animals, *Ansted's Ancient World, p. 348. 279. Igneous rocks are found abundantly in connexion with the Tertiary series; they are lavas of extinct volcanoes, and are intermediate in character between the traps of the secondary period and the products of active volcanoes. In composition they are principally trachytic, but sometimes scoriaceous, or tufaceous. One of the most remarkable localities of Tertiary volcanoes is an extensive plain in Auvergne, central France, which supports a series of seventy volcanic cones, varying from five hundred to a thousand feet in height, forming a range about twenty miles long and two broad. Many of these cones retain well defined craters several hundred feet deep, and their lava beds can be traced as casily as those of Vesuvius. "There is no spot," says Mr. Scrope," even among the Phlegræcan fields of Italy, which more strikingly displays the characters of volcanic desolation. Although the cones are partially covered with wood and herbage, yet the sides of many are still naked; and the interior of their broken craters, rugged, black and scorified, as well as the rocky floods of lava with which they have loaded the plain, have a freshness of aspect, such as the products of fire alone could have so long preserved, and offer a striking picture of the operation of this element in all its most terrible energy." These volcanic vents are of different ages; some of them are manifestly of comparatively recent origin. 280. Another interesting group of Tertiary volcanoes is upon the banks of the Rhine, where the graceful forms of the Siebengebirge or Seven Mountains, and the majestic Eifel with its crater covered with scoriæ, and its lava currents still visible, are conspicuous features in the picturesque scenery of the river. The basis rocks supporting the Tertiary formations are not here, as in Auvergne, granite, |