dinornis. This preponderance of bulky frameworks, and the number of intermediate forms that serve as connecting links between species now widely separate, are perhaps the most notable features of the tertiary fauna, and are highly suggestive to the physiologist, who, rising above mere description, strives to attain to the higher knowledge of creational method and law.

The diversified latitudes over which tertiary deposits are spread, and the difficulty of assigning a contemporaneity to strata containing few or no species in common, compels the palæontologist often to deal with the details of the respective areas rather than attempt a generalised expression for the whole. Enough for our outline, however, to remark that as sea and land approach their present configuration, the fossil flora and fauna begin in like manner to assume that distinctive impress which now characterises existing nature. As already stated, many of the Old World forms are unknown in the New; some of those that characterise the tertiaries of India are unknown in the strata of Europe; and only a few, and these during the earlier stages of the period, appear to have anything like a cosmopolitan extension. So also in the earliest or eocene stage the number of existing species are few compared with the extinct; this proportion increases in the middle stages; and as we rise to the uppermost deposits, it is often difficult to draw any specific distinction between the fossils they contain and the plants and animals that now flourish on their superficial areas. In the earliest stages the fauna of Europe was characterised by its palæotheres, anoplotheres, xiphodons, river-hogs, alligators, crocodiles, gavials, and turtles ; in the middle stages these decline or die out, and deinotheres, mastodons, mammoths, camels, giraffes, cave-bears, lions, and hyænas take their places; while in the upper stages

K 2

many of these decline, and mammoths, hippopotami, rhinoceroses, deer, wild oxen, horse, bears, and tigers become the dominant features. In like manner, when we turn to Asia, we can trace a similar ascent from the earlier stages, which contain many forms in common with those of Europe, to the middle stages, characterised by their numerous forms of elephant, sivatheres, bramatheres, camels, giraffe, lion, tiger,

monkey, crocodiles, and tortoises of enormous magnitude; and from these again to the upper stages, where the mammoth, rhinoceros, urus, horse, ass, and other creatures lead insensibly to the existing forms of that gigantic continent. In the same way it will be found with Africa, when geology has carried her researches further into that littleknown region; and so also it has been found in North

America, whose forms bear a wonderful parallelism to those of Europe; while in South America a similar gradation will yet be determined upward to those Pampean flats, whose pliocene clays and gravels have yielded those wonderful megatheres, mylodons, toxodons, glyptodons, mac

rauchenes, and other mammals, whose congeneric forms now people, in diminutive scale, the plains and forests and uplands of that exuberant continent. As with the larger

continents, so with smaller and more detached areas. The marsupials of Australia have their forerunner in the gigan

preceded by palapteryx and dinornis; and the still more gigantic æpyornis of Madagascar foreshadows the advent of the ostrich of Africa.

In the elimination of these successive fauna long ages must have passed away; and during these ages vast physical changes were necessarily effected on the terraqueous relations of the globe. In the northern hemisphere, some of the principal mountain-chains-the Alps, Apennines, Carpathians, and Himalayas—had been gradually assuming their ultimate configuration; and the large inland seas that had occupied the central latitudes of Europe, of Northern Africa, Middle India, and Eastern Siberia and China, had been elevated successively into shoals, lake, and island, swamp and dry land. Simultaneously with these terraqueous changes, the genial temperature that ushered in the eocene period of Europe and America began, stage by stage, to decline; the miocene was marked by more temperate manifestations; and ultimately the pliocene sank into a condition incompatible with the existence of the former flora and fauna. A cold, glacial, and barren period ensued, and under its rigours pliocene life in the northern hemisphere succumbed, and was succeeded by genera and species akin to those that now people the boreal regions.

This ungenial period, generally known in geology as the "Glacial," "Northern Drift," or "Boulder Clay" epoch, is lithologically characterised by its superficial mounds and masses of drift-sand and gravel, by thick tenacious clays, interspersed indiscriminately with water-worn blocks of all sizes, from mere pebbles to boulders many tons in weight, and by the polished, rounded, and striated surfaces of the subjacent rocks, as if they had been subjected to the longcontinued friction of water or ice-borne material, and scratched and furrowed by the passage of the harder and