they are of lacustrine origin, and show that in what is now the heart of the Continent the bed of the Cretaceous sea was upraised into a succession of vast lakes, round which grew a luxuriant vegetation. In these lakes a total mass of Eocene strata, estimated at not less than 12,000 feet, was deposited, entombing and preserving an extraordinarily abundant and varied record of the plant and animal life of the time. The flora of Eocene time points to a somewhat tropical climate. Among its plants are many which have living representatives now in the hotter parts of India, Australia, Africa, and America. Above the ferns (Lygodium, Asplenium, etc.), which clustered below, rose clumps of palms, cactuses, and aroids; numerous conifers and other evergreens gave the foliage an umbrageous aspect, while many deciduous trees ancestors of some of the familiar forms of our woodlands-raised their branches to the sun. Among the conifers were many cypress-like trees (Callitris, Cupressinites), pines (Pinus, Sequoia), and yews (Salisburia or Ginko). Species of aloe (Agave), sarsaparilla (Smilax), and amomum were mingled with fan-palms (Sabal, Chamarops) and screw-pines (Pandanus, Nipa), together with early forms of fig (Ficus), elm (Ulmus), poplar (Populus), willow (Salix), hazel (Corylus), hornbeam (Car FIG. 193.- Eocene Plant pinus), chestnut (Castanea), beech (Petrophiloides Richard- (Fagus), plane (Platanus), walnut sonii), natural size. (Juglans), liquidambar, magnolia, proteaceous plants (Fig. 193) resembling those of Australia and the Cape, water-bean (Nelumbium), water-lily (Victoria), maple (Acer), gum-tree (Eucalyptus), cotoneaster, plum (Prunus), almond (Amygdalus), laurel (Laurus), cinnamontree (Cinnamomum), and many more. The fauna likewise points to the extension of a warm climate over regions that are now entirely temperate. This is particularly noticeable with regard to the mollusca. The species are, with perhaps a few exceptions, all extinct, but many of the genera are still living in the warmer seas of the globe. Some of the most characteristic forms are species of Nautilus, Oliva, Voluta, Conus, Mitra, Cyrena, FIG. 194. Eocene Molluscs; (a) Oliva Branderi (natural size); (b) Cytherea, Chama. The genus of Foraminifera, called in older Tertiary time spread across the heart of the Old World from the Atlantic to the Pacific Oceans, for the limestone in question is largely composed of their remains. Some of the most common fish-remains found in the Eocene strata belong to the genera Lamna, Otodus, Myliobates, Pristis. Reptilian life, which enjoyed such a preponderance during the Mesozoic ages, is conspicuously diminished in the Eocene deposits alike in number of individuals and variety of structure. The genera are chiefly turtles, tortoises, crocodiles, and sea-snakes, presenting in their general assemblage a decidedly modern aspect compared with the reptilian fauna of the Secondary rocks. Remains of birds are comparatively rare as fossils. We have seen that the earliest known type has been obtained in the Jurassic system, and that others have been found in the Cretaceous rocks. Still more modern forms occur in Eocene strata; they include one (Argillornis) which may have been a forerunner of the living albatross; another, of large size (Dasornis), akin to the gigantic extinct ostrich-like moa (Dinornis) of New Zealand; a third (Agnopterus) shows an affinity with the flamingo; while the buzzard, woodcock, quail, pelican, ibis, and African hornbill are represented by ancestral forms. That the early type which linked birds with reptiles was still living is shown by the remains of one curious genus (Odontopteryx) which had toothed jaws like those of the pterosaurs. But it was chiefly in its higher forms of life that the fauna of early Tertiary time stood out in strong contrast with that of the previous ages of geological history. The mammalia now took the leading place in the animal world, which they have retained ever since. Among the Eocene mammals reference may here be made to the numerous tapir-like creatures which then flourished (Coryphodon, Palæotherium, Fig. 195, Anchitherium, etc.) Some of the forms FIG. 195.-Eocene Mammal (Palæotherium magnum, 37). were intermediate in character between tapirs and horses, and included the supposed ancestors of the modern horsesmall pony-like animals, with three, four, and even traces of five toes on each foot. Many of the mammals had decidedly marsupial characters, though otherwise resembling wolves, foxes, wolverines, and other modern forms. There were likewise true opossums. Numerous herds of hog-like animals (Hyopotamus) and of hornless deer and antelopes (Dichobune, etc.) wandered over the land, while in the woodlands lived early ancestors of our present squirrels, hedgehogs, bats, and lemurs. Among these various tribes which recall existing genera others of strange and long extinct types roamed along the borders of the great lakes in Western North America. The Tillodonts were a remarkable order, in which the characters of the ungulates, rodents, and carnivores were curiously combined. These animals, perhaps rather less in size than the living tapir, had skeletons resembling those of carnivores, but with large prominent incisor teeth like those of rodents, and with molar teeth possessing grinding crowns like those of ungulates. Still FIG. 196. -Skull of Tinoceras ingens (about 11). more extraordinary were the forms to which the name of Deinocerata has been given (Deinoceras, Tinoceras, Fig. 196). These were somewhat like elephants in size, and like rhinoceroses in general build, but the skull bore a pair of horn-like projections on the snout, another pair on the forehead, and one on each cheek. The Eocene rocks of England are confined to the southeastern part of the country, from the coast of Hampshire into Norfolk. They vary in character from district to district, sands and gravels being replaced by clays according |