In the cretaceous beds, which are chiefly deep sea deposits, the remains of plants and land animals are comparatively rare. The wealden beds, however, which had a fresh-water origin, contain the remains of several small marsupials, some huge carnivor ous and herbivorous reptiles, a few fresh-water shells, and some fragments of drift-wood. The true chalk is remarkably abundant in the remains of foraminifers—indeed, in some places, it is composed almost entirely of the shells of these minute creatures. Of the 'nausea, the brachiopoda are in some beds very abundant; the cenchifera introduce several new forms, the most striking of which is the genus hippurites, which with its allies did not survive this period; the cephalopodous genera which appeared in the oolite continue to abound in the chalk, many new fo'rms being introduced; while others dis appear with the period, like the beleinnitcs and ammonites. Sea-u•ehins become still more numerous. In some beds the remains of fish are abundant, and while cartilaginous species still exist, the bony fishes become more numerous; and among them the family to which the salmon and cod belong makes its appearance. Reptiles are common in the wealden, and the flying pterodactyls attained a greater size, and were probably more numerous than in the former period. The remains of a single bird has been obtained from the greensand, but with this exception, birds as well as mammals have left n4 traces that have yet been found in the cretaceous beds, though doubtless they existed.
In the tertiary strata, the genera are either those still living, or forms very closely allied to them, which can be separated only by the careful examination of the accurate scientific observer. The plants of the eocene beds are represented by dicotyledonous leaves, and palm and other fruits. Foraminifers are remarkably abundant, whole moun tain masses being formed of the large genus nummulites. Brachiopeda are rare, but conehifera, gasteropoda, and cephalopoda increase in number; the new forms hieing gen erically almost identical with those now living. The principal living orders of fish, rep tiles, and birds are represented in the eocene strata. A considerable variety of pachydermatous mammals, suited apparently to live on marshy grounds and the borders of lakes, have been,found in France and England, and associated with theta are some carnivorous animals, whose remains are, however, much rarer. An opossum has been found at Colchester. The fragments belonging to the supposed monkey are portions of a small pachyderm, hyracotherium (q.v.).
Little need he said of the invcrtehrata of the miocene period, beyond remarking their growing identity in genera with the living forms. Among the mammals, the quadru mane make their first appearanee. The true elephant and the allied mastodon are rep resented by several species; a hinge carnivorous whale has been discovered, and several carnivora and deer, with a huge edentate animal, have been described. Owen thus speaks of these animals: "Our knowledge of the progression of mammalian life during the miocene pe•ind, teaches us that one or two of the generic forms most frequent in the older tertiary strata still liT.ered on the earth, but that the rest of the eocene mammalia had been superseded by new forms. some of which present characters intermediate between those of eocene and those of plioane genera." In passing upwards through the tertiary strata, the organic remains become more and more identical with living forms, so that when we reach the pliocene and pleistocene periods, the great proportion of the invertebrata are the same species which are found occupying the present seas. Among the hither orders of animals the life of a species is much shorter than in the lower, and consequently, though the vertebrate approach so nearly to existing forms as for the most part to be placed in the same genera, yet the species differ from any ofthe living representatives of the different genera.
The Suffolk " crags," which are the only British representatives of the pliocene period, contain the relics of a marine testecea, that differs little from the present tenants of the European seas, between 60 and 70 per cent being the same species. The ear-bones of oue or more species of cetacea have been found, and at Antwerp, the remains of a dolphin have been discovered in beds of this age.
The various local deposits which together form the pleistocene strata, the latest of the geological periods, contain a great variety of organic remains. In the submarine forests and in beds of peat, the stumps of trees are associated with the remains of underwood and herbaceous plants of species still living. Nearly all the molluscs and other marine invertebrata still survive. It is among the vertebrata -that the most remarkable forms appear—forms which in the main differ little from the existing race of animals except in their enormous size. Elephants and rhinoceroses, fitted for a cold climate by their cov ering of song coarse hair and wool, roamed over the northern regions of both the old and the new world, and were associated with animals belonging to genera which still exist in the same region, as bears, deer, wolves, foxes, badgers, otters, wolverines, wea sels, and beavers, besides others whose representatives are now found further south, as the hippopotamus, tapir, and hyena. Contemporary with these, there lived in South America a group of animals which were types in everything but in size of the peculiar existing fauna of that continent. Among these were gigantic sloth-like animals, fitted to root up and push down the trees, instead of climbing to strip them of their foliage, like time sloth. The armadillo was represented by the huge glyptodon, whose body was protected by a strong tessellated coat of mail. The species of fossil tapirs and peccaries are more numerous than their living representatives. The llamas were preceded by the large macrauchenia, and the opossums and platyrhine monkeys were also prefigured by related species. Besides these, there have been found the remains of two mastodons and a horse, none of which are represented by any indigenous living animal in South America. The peculiar group of animals confined to Australia were prefigured by huge marsupials, some having close analogies to the living kangaroos and wombats, while oth ers were related to the carnivorous native tiger. The gigantic wingless birds of New Zealand correspond in type with the anomalous apteryx, now existing only on these islands.
Associated with the remains of elephants, mastodons, cave-bears, and cave-hyenas, there have been found in England and France, numerous specimens of flint implements, which are undoubtedly the result of human workmanship, and show at least that man was contemporaneous with these extinct animals. If more certain evidence were needed of this, it has been obtained in the discovery of flint implements, bone implements fash ioned and carved by means of the flint knives, the horns of a reindeer, two kinds of extinct deer, bus primigenius, and other animals, associated with numerous bones of man, included in the breccia of the cave of Bruniquel in France. Owen considers the evidence of the contemporaneity of the various remains as conclusive. The several human skulls which have been obtained show, acccording to the same authority, no characters whatever indicative of an inferior or transitional type. There are no certain data to give probability to the guesses which have been made as to the number of years which have elapsed since these deposits in which the relies of man occur were formed. The whole inquiry, moreover, is so recent, and the accumulation of facts is almost every day going on, that it would be premature to speak dogmatically on the subject.