Early Man in Britain and His Place in the Tertiary Period/Chapter 2

CHAPTER II.

BIOLOGICAL AND PHYSICAL CHANGES IN BRITAIN BEFORE THE ARRIVAL OF MAN.—THE EOCENE PERIOD.

The Eocene Classification.—South-Eastern Coast-Line of Britain.—Eocene Sea-Board of Britain.—The Eocene Sea.—Britain connected with America.—The Mountains.—The Rivers.—The Lower Eocene Plants and Animals.— The Lower Eocene Birds.—The Mid Eocene Flora.—The Mid Eocene Mammalia.—British Upper Eocene Mammals.—Upper Eocene Mammalia of the Continent.—The Order Primates represented.—Climate of Britain Tropical.—General Conclusions.—Man not here.

The close of the Secondary age, as we have observed in the preceding chapter, was marked by great changes in the physical geography of Europe. The cretaceous rocks, which had been formed at the bottom of a deep sea, were lifted up above the waves, and plants and animals hitherto unknown appeared on the new continent. The new invaders took possession of the land, the air, and the sea, and brought about as marked a change in the European fauna as that in geography which had preceded their arrival.

It is very probable that the elevation of the bottom of the sea, by which this immigration of new forms became possible, was accompanied by a corresponding depression of a neighbouring tract of land, like that which took place in the Pleistocene age,[1] when the Sahara Desert was covered by the sea, and a large part of the Mediterranean area was dry laud, or like that now taking place in the Scandinavian peninsula, which is being lifted up from the North Cape to Stockholm, and depressed in the south, in Scania.[2] New conditions of life were produced by these changes, so unfavourable for the Secondary animals, that all the higher forms perished that were unable to compete in the struggle for life with the new invaders, whose presence marks the Eocene period. The invasion of Europe by the placental mammals is the great event which is the natural starting-point for our enquiry into the ancient history of man, since the conditions by which he was surrounded on his arrival in Europe, form part of a continuous sequence of changes, from that remote period down to the present day. Each of these changes in life and geography will be treated in outline in its due place in this work.

The Eocene Classification.

The Eocene period has been defined in the last chapter as that in which the existing orders and families of the placental mammalia appear for the first time. The Eocene marsupials, however, are, as may be expected from their class having appeared in the Secondary age, in a far more advanced stage of evolution, being represented by a living genus,[3] the opossum, as well as by other forms intermediate between the marsupials and the true placental mammals.


Fig. 2. Nummulites lævigata. Bracklesham, 1/1.
The Eocene strata[4] are found in the area to the south-east of a line passing from the Wash to Charmouth in Dorsetshire, and are mainly centered in two basins, named, respectively, that of London, and that of Hampshire and the Isle of Wight. They occur over a very wide area on the continent. They are divided into three groups, the lower or Pre-nummulitic, the middle or the Nummulitic, and the upper or the Post-nummulitic, the widely spread foraminifer, Nummulites (Fig. 2), offering a ready means of determination of age, not merely in Europe, but throughout Asia, and a large part of Africa. The following table represents the thickness, characters, and conditions of deposit of each of the subdivisions in England, together with their equivalents in France, as determined by the recent researches of Professor Gaudry.

Classification of British Eocene Strata.

1. Upper Eocene or Post-nummulitic = Proicène (Gervais).
Thickness
in Feet.
Conditions of Deposit. French Equilavents (Gaudry).
  1. Hempstead Marls, Clays, Sands
    ................................................................................................................................................................................................................................................................................................................................................................................................
170
  1. Freshwater, Estuarine, Marine
    ................................................................................................................................................................................................................................................................................................................................................................................................
  1. Bembridge Marls, Sands, Limestone
    ................................................................................................................................................................................................................................................................................................................................................................................................
80
  1. Freshwater, Estuarine, Marine
    ................................................................................................................................................................................................................................................................................................................................................................................................
6e Étage du Gypse de Paris.
  1. Osborne or St. Helena Marls, Clays
    ................................................................................................................................................................................................................................................................................................................................................................................................
100
  1. Freshwater, Estuarine
    ................................................................................................................................................................................................................................................................................................................................................................................................
  1. Headon Marls, Sands, Clays
    ................................................................................................................................................................................................................................................................................................................................................................................................
260
  1. Freshwater, Estuarine, Marine
    ................................................................................................................................................................................................................................................................................................................................................................................................
2. Middle Eocene or Post-nummulitic = Eocène (Gervais).
  1. Barton Sands, Clays
    ................................................................................................................................................................................................................................................................................................................................................................................................
300
  1. Marine
    ................................................................................................................................................................................................................................................................................................................................................................................................
5e Étage des Sables de Beauchamp.
Bracklesham
Bagshot
  1. Sands, Clays
    ................................................................................................................................................................................................................................................................................................................................................................................................
?
  1. Marine
    ................................................................................................................................................................................................................................................................................................................................................................................................
4e Étage du Calcaire Grosier de Paris.
Alum Bay and
Bournemouth
  1. Sands, Clays
    ................................................................................................................................................................................................................................................................................................................................................................................................
?
  1. Freshwater, Estuarine, Marine.
    ................................................................................................................................................................................................................................................................................................................................................................................................
3. Lower Eocene or Pre-nummulitic = Orthocène (Gervais).
  1. London Clay
    ................................................................................................................................................................................................................................................................................................................................................................................................
480
  1. Estuarine, Marine
    ................................................................................................................................................................................................................................................................................................................................................................................................
3e Étage des Sables de Cuyse-la-Motte, Sables de Soissonnais.
  1. Woolwich and Reading Sands, Clays, Plastic clays
    ................................................................................................................................................................................................................................................................................................................................................................................................
58
  1. Freshwater, Estuarine, Marine
    ................................................................................................................................................................................................................................................................................................................................................................................................
2e Étage des Lignites du Soissonnais.
  1. Thanet Sand
    ................................................................................................................................................................................................................................................................................................................................................................................................
39
  1. Marine
    ................................................................................................................................................................................................................................................................................................................................................................................................
1e Étage des Gres de la Fère.

South-Eastern Coast-Line of Britain.

We may gather from the alternation and repetition of beds deposited by fresh, brackish, and salt water, in the above table, the important fact that south-eastern England was traversed by a fluctuating shore during the whole of the Eocene age, while to the north-west of the line above mentioned there were no geographical changes sufficiently great to leave any permanent mark in the geological record. On the continent, however, great oscillations of level took place. The Pre-nummulitic age was a period of elevation, followed in the Nummulitic by a great depression beneath the waves of the sea, followed in its turn by a period of re-elevation. None of these movements have left any trace in Britain, in the area to the north-west of the above-mentioned line, consequently this may be taken to be that of the Eocene sea-board of Britain. Its exact position varied from time to time, and considerable additions were made to the land, more particularly in the Post-nummulitic times, by the accumulation of shoals and alluvia, like those by which large tracts have been added to Great Britain since the invasion of the Romans, such as that joining the Isle of Sheppey to the mainland of Kent, or that which has converted the Roman port of Anderida into the green pastures running close under the ramparts of Pevensey Castle. By this means, as well as by movements of elevation and depression, frequent changes took place in the shallow Eocene sea.

The Eocene Sea.

We have no evidence that the Eocene sea touched any part of the present area of Great Britain, excepting that represented in the Map (Fig. 3) in its period of maximum extension.

Early Man in Britain and His Place in the Tertiary Period - Fig. 3.—Geography of North-Western Europe in the Eocene Age.png

Fig. 3.—Geography of North-Western Europe in the Eocene Age.

According to the observations of Mr. Sorby[5] on the marine currents, the sea in which the Post-nummulitic rocks of the Isle of Wight were deposited was shut off from the Atlantic by a barrier of land running due south from Dorset, Devon, and Cornwall, towards Normandy and Brittany, the main body of the ocean being to the east or south-east, and extending at least as far to the north as Denmark.

This sea teemed with life of various kinds, now to be found, for the most part, in the warmer regions of the ocean. Gigantic sharks, rays, sword-fishes, and sturgeons, and the peculiar armour-clad fish the Lepidosteus, found their prey in vast abundance. There were turtles also innumerable, and sea-snakes, some of which (Palæophis) were twelve feet long. Among the more important mollusca we may notice the nautilus, the cone, volute, cowrie, olive, and large spindle shells (Fusus), which belong to the marine fauna of the tropics.

The Eocene lakes, rivers, and seas were singularly rich in reptilian life. "More true turtles," writes Professor Owen,[6] "have left their remains in the London Clay, at the mouth of the Thames, than are now known to exist in the whole world; one (Chelone gigas) is of enormous size, with a head upwards of a yard across. Emys and Platemys haunted the rivers, while the estuaries were the feeding-places of the soft turtles (Trionyx), and basking on the shores were to be seen crocodiles, alligators, and the long-snouted gavial, now only living in the rivers of India."

Britain connected with North America.

From the coast-line above mentioned the land extended northwards and westwards, far away from our present shores, and is proved by the examination of the forests and of the animals to have been continuous with the North American continent. The chief botanists[7] of the present time—Hooker, Dyer, Saporta, Dawson, and Asa Gray—are agreed that the north polar region was the centre from which the Tertiary floras have been dispersed over the new and old worlds. According to Saporta, the marked difference between summer and winter in the polar regions has first left its impress in the dicotyledons with deciduous leaves, which were unknown on the earth before the Cretaceous age. Their introduction was the greatest revolution in the vegetable kingdom, as yet observed, and when once evolved they increased rapidly in numbers and diversity of forms. As the polar temperature was lowered, the trees of warm habit were pushed farther and farther south, away from their original birthplace, and ultimately only survived in isolated districts, now separated from each other by great tracts of sea, or great areas of desert or of mountain. In consequence of this there is an almost unbroken sequence to be observed in the floras succeeding each other in the northern hemisphere, from the Eocene age down to the present day. "There is no great break," as Mr. Starkie Gardner observes, "in passing from one to the other, when we compare them over many latitudes, and but little change beyond that brought about by altered temperature or migration. If Tertiary floras of different ages are met with in one area, great changes, on the contrary, are seen, and these are mainly due to progressive changes in climate. From middle Eocene to Meiocene the heat imperceptibly diminished. Very gradually the tropical members of the flora disappeared; that is to say, they migrated, for most of their types, I think, actually survive at the present day, many but very slightly altered. Then the sub-tropical members decreased, and the temperate forms, never quite absent even in the middle Eocenes, preponderated. As decreasing temperature drove the tropical forms south, the more northern must have pressed closely upon them. The northern Eocene, or the temperate floras of that period, must have pushed from their homes in the far north more and more south as climates chilled, and at last, in the Meiocene time, occupied our latitudes. The relative preponderance of these elements, I believe, will assist in determining the age of Tertiary deposits in Europe, more than any minute comparisons of species. Thus it is useless to seek in the Arctic regions for Eocene floras, as we know them in our latitudes; for during the Tertiary period the climatic conditions of the earth did not permit their growth there."[8]

Before such a migration of plants as this could take place there must have been land extending far north, so as to bring Europe into close relation with the Polar regions. The position of this ancient continent is indicated by the fossil floras of Iceland, Greenland, and Spitzbergen, which flourished in those latitudes in the Eocene, and subsequently established themselves in Europe in the Meiocene age, as we shall see in the next chapter.[9] Mr. Starkie Gardner places the land barrier which shut off the Atlantic from the Arctic Sea, between the 60th and 70th degrees of N. latitude, or in the position in which it is represented in the accompanying map (Fig. 3).[10]

The forms of animal life also common to Britain and America prove a connection between the two regions in the Eocene age. The opossum of Eocene Britain, the extinct Coryphodon, Lophiodon, Anchithere, and Anoplothere, are common to both, and the alligator, which haunted the rivers of the south of England, the bony pike, the last representative of the armour-clad fishes of the Secondary period, and a little snail (Helix labyrinthica), have found a refuge in America from those agencies by which they have been exterminated in Europe.

For the migration of these animals there must have been a continuous tract of land between Britain and America; and the direction of this is pointed out by the soundings in the Atlantic and the Northern seas (see Map, Fig. 3). It is indicated by the ridge of land at a depth of 500 fathoms sweeping away northwards from the west of Ireland, past the Faroe Islands to the south of Iceland and Greenland. On the eastern side of this the observations taken in the Norwegian Deep Sea Expedition in 1877 prove the existence of deep water between Jan Mayen Land and Spitzbergen, and between that island and Norway; the soundings being respectively 2650 and 1760 fathoms.[11] The elevation of this tract of land would afford a means of free migration of animals, and plants from Europe to America, or from America to Europe. I have therefore taken the 500-fathom line to mark the probable boundary of the Eocene Atlantic, as well as the southern extension of the Eocene North Sea in the direction of the Shetlands. The enormous depth of the Atlantic between Ireland and the United States forbids the hypothesis that the line of communication was in that direction.

From these considerations Eocene Britain may be taken to have formed part of a great continent, extending northwards and westwards to America by way of Iceland and Greenland, while to the north-east it was continuous with Norway and Spitzbergen. It extended also to the south-west, across what is now the Channel, to join the western parts of France. This great north-western continent, or northern Atlantis as it may be termed, existed through the Eocene and Meiocene ages, offering a means of free migration for plants and animals, and it was not finally broken up by submergence, as we shall see in the course of this work, until the beginning of the Pleiocene age.

The Mountains.

The highlands of Britain in the Eocene age were in their present positions. The older Palæozoic strata of Cornwall, Wales, Cumberland, and Scotland had already been cut up into hill and valley before the deposit of the Triassic rocks, and constituted a broken chain of mountains on the west, during the whole of the Secondary period. The Pennine range, the backbone of England, was then very much as it is now, with its limestone cut into deep canons or dales in the areas of Derbyshire and Yorkshire, and with the massive carboniferous sandstones rising into rugged heights, and traversed by deeply cut glens. The hills of Somerset, Devon, and Ireland also, were the same, and the surface contours of the lower ground must have been to a large extent what they are now, since they were carved by those agents by which the present hills and valleys have been formed. There are, however, differences to be remarked. The mountains were higher[12] and more precipitous, and the landscape could not, in those times, have offered the flowing lines and curves, which have been produced by ice, in the present surface. Nor must it be forgotten that in the long lapse of ages the whole of the Eocene land-surface has been removed by the action of those denuding agents, which we shall bring before our readers in treating of the Meiocene mountains.

From Professor Judd's observations on the western districts of Scotland, it is evident that the volcanic energy which raised a range of lofty volcanic mountains in the Western Isles in the Meiocene age, was felt in the same districts in the Eocene. We may therefore picture to ourselves groups of cones, similar to those of Auvergne, rising above the forests, then spreading from the rugged Alpine heights of the Western Highlands far away in one mass of green, broken only by the rivers, to Ireland and the remote coast-line of the western sea.

The Rivers.

Since the higher grounds in Great Britain in the Eocene time were in their present positions, it will follow that the watersheds of the principal rivers were then very much as they are now, so far as relates to their upper courses. On the western side of the Pennine mountain axis the Ribble, Mersey, Dee, and Severn fell then, as now, into the Atlantic, after traversing the broad valleys reaching to the line of cliffs off the west of Ireland. Those on the east fell into the south-eastern sea (see Map, Fig. 3), probably joining some of those of Norway, and contributing to form the great river which was the chosen haunt of the alligator and the crocodile, and which flowed through the dense forests of palms and banksias, then covering the Eocene continent in these latitudes. The lower course, however, of the Trent was determined by movements of level, which took place in Post-meiocene times, and the river Thames, as Professor Ramsay has pointed out, came into being also after the close of the Meiocene age.

The Lower Eocene Plants and Animals.

The lower Eocene vegetation[13] in Britain preserved in the London Clay was, as Professor Heer observes, of a tropical and Indo-Australian character. The forests were composed of palms of various sorts (Palmacites, Flabellaria, Nipadites), the last of which is now represented only by the Nipa fruticans of the banks of rivers in India and the Philippines. There were cypresses (Solenostrobus, Frenelites, Callitritis) also allied to genera living in Tasmania, and proteaceous plants allied to the banksia, maples, poplars, and mimosas, as well as custard apples, gourds, and melons, and ferns closely related to the living Osmunda regalis. This luxuriant and tropical vegetation has been proved by the recent discoveries of Mr. Starkie Gardner, in the Pre-nummulitic deposits at Newhaven, to have flourished in the British area, and not to have been swept down, as was formerly supposed, by a river flowing from a tropical region far away to the south. In the London Clay of Sheppey it is represented mainly by fossil fruits, in the strata at Newhaven principally by leaves which show no sign of having been conveyed long distances by water.

The Lower Eocene Mammalia.

The earliest Eocene mammals[14] found in Britain consist of marsupials and a creature belonging to an extinct family of the odd-toed (Perissodactyle) sub-order of Herbivores. The opossum (Didelphys Colchesteri) is to be looked upon as a survival from the Secondary fauna, and the Hyracotherium, a small animal with a skull the size of that of a hare, canine teeth resembling those of a peccari, and a form intermediate between that of the hog and the hyrax or coney. Both occur in the Woolwich and Reading series of the Table (p. 16), at Kyson in Suffolk. The Pliolophus of the London Clay is closely allied to the latter, while the Coryphodon from the same stratum resembled a tapir in its dentition and skeleton.

In the corresponding strata in France two[15] beasts of prey of decided marsupial affinities are met with, the Arctocyon primævus, the most ancient of the Tertiary mammals of Europe, allied to the bears in the structure of its teeth, and to the marsupials in the low organisation of its brain, and the Palæonictis, with teeth resembling those of the Tasmanian dasyure, and in size rivalling the wolverine or glutton. The latter may very well be taken to be the type from which the family of Civets have been derived. The tapir-like Coryphodon also inhabited the lower Eocene land of France, Switzerland, and North America.[16]

These animals constitute a small and insignificant fragment of a fauna, the ancestry of which is to be looked for in the Cretaceous age. They are of peculiar interest, because they show that at this time the carnivores were intermediate in character between the marsupials and the placental mammals.

The Lower Eocene Birds.

The lower Eocene birds, like the placental mammals identified by Professors Owen[17] and Milne Edwards,[18] belong to extinct genera. In Britain the rivers were haunted by large goose-like birds (Odontopteryx) with the beak armed with curious tooth-like processes, by herons, and by kingfishers (Halcyornis). There were flights of gulls on the sea, and on the land were to be seen vultures (Lithornis) and a great bird (Dasornis) resembling in the size of its head the moa of New Zealand. In France the Gastornis, of the size of an ostrich,[19] "but more robust and with affinities to wading and aquatic birds," inhabited the banks of the rivers.

The Mid Eocene Flora.

The mid Eocene land in Britain was covered with a rich and luxuriant vegetation[20] like that of the tropics, in which evergreen forest trees abound. The leaf beds of Alum Bay in the Isle of Wight, and of Bournemouth in Hampshire, enable us to form a definite idea of the forests (Fig. 4) which extended from the margin of the Nummulitic sea far away inland, clothing hill and valley with a dense mantle of green. Here cypresses, yews, and pines raised aloft their dark-green foliage; there the screw-pine (Pandanus), fan-palms, and
Early Man in Britain and His Place in the Tertiary Period - Fig. 4.—Mid Eocene Forest of Bournemouth, overlooking Lagoon.png

Fig. 4.—Mid Eocene Forest of Bournemouth, overlooking Lagoon.

feather-palms were conspicuous. Gigantic aroids were also to be seen, and various representatives of the family of Sarsaparilla. There were groves of poplars, elms, laurels, oaks, hornbeams, beeches, chestnuts, willows, planes, figs, buckthorns, walnuts, maples, spindle-trees, and bread- fruits. The Celtis or nettle-tree, several sorts of banksia, and the Eucalyptus or gum-tree, may be noted among the remarkable Australian genera presented by the flora. Giant cacti also raised their forms like the huge candelabra that overlook the arid deserts of New Mexico. The tree trunks were garlanded with large creepers belonging to the tropical families of Porana and Bignonia.

A similar group of vegetation has been identified by Dr. Heer from Monte Bolca in Lombardy, from which it may be inferred that the climate of Europe was more uniform in mid Eocene times than it is at the present day.

The Mid Eocene Mammalia.

These forests afforded shelter and food to a fauna of which very scant traces have been identified. In this country the Lophiodon of Bracklesham, an animal resembling the tapir in general appearance, and presenting great variations in size, is the only well-defined mammalian species. In France[21] it is associated with two tapiroid genera (Pachynolophus, Pro-palæotherium), and animals allied to the hogs and omnivorous carnivores (Anchilophus, Dichobune, Heterohyus). There also were true carnivores of uncertain affinities, one as large as a lion, a second about the size of a badger, and a third very much smaller, while a fourth was remarkable for its compressed and serrated canines, like those of the Machairodus, or sabre-toothed lion haunting the Meiocene, Pleiocene, and Pleistocene forests of Europe.

British Upper Eocene Mammals.

At the close of the mid Eocene period there was a general elevation of the continent, in which the southern parts of Britain participated, the coast-line being pushed farther to the south, and the area which had been occupied by the south-eastern sea being covered with the fresh waters of a river. The frequent alternation of marine and fresh water deposits in the Isle of Wight, in Hampshire, and in Sussex, show that those districts were then constantly subject to oscillations of level.

The vegetation covering the southern parts of Britain is imperfectly known, but from the few fragments which are preserved it was, probably, closely allied to that of the mid (Fig. 4) and lower Eocene. In the Isle of Wight the forests were to some extent composed of palms. The mammals, however, present differences of the very highest importance. Instead of the solitary Lophiodon which happens to have been found in the deposits of the Nummulitic sea, the remains of a varied mammalian fauna have been discovered in the south of England. Animals (Palæotherium) like the tapirs of tropical Asia and America wandered in the forests and on the banks of the rivers (Fig. 5). There were also herds of Anchitheres, which have been proved by the researches of Professors Marsh and Huxley[22] to have been the ancestors of the horse. They were about the size of Shetland ponies, and possessed three distinct hoofs on each foot, reaching to the ground. The forests also sheltered numerous hog-like animals, such as the Chœropotamus, intermediate between the swine and the hippopotamus, and the Microchœrus and Hyopotamus. Generalised, or rather, as they may with more justice be termed, ancestral forms of the deer and antelopes, hornless and without antlers (Anoplotherium, Dichodon, Dichobune) browsed on the luxuriant herbage in the glades. Overhead on the trees there were opossums, while in the undergrowth lurked the Theridomys, a creature allied to the small spiny rats (Echimys) of Brazil. There were also beasts of prey, one the Hyœnodon, or precursor of the hyæna, a carnivore, which to the ordinary characters of a placental mammal united the marsupial attribute of three sectorial molars in each jaw, arranged as in the marsupial Thylacinus or Tasmanian wolf, which it rivalled in size.

Upper Eocene Mammadia of the Continent.

The same group of animals lived on the borders of the lake occupying the site of Paris in the upper Eocene times, and the species associated with them enable us to complete our picture. There were small deer-like animals, the Kainothere and the Amphitragulus, closely allied in size and form to the musk-deer, as well as the Xiphodon (Fig. 5), in elegance rivalling the gazelle. Among the carnivores were creatures resembling wolves (Cynodon), foxes (Amphicyon), wolverines (Tylodon), and hyænas and civets (Proviverra), all with characters like the Hyœnodon, now only found among the Marsupials. According to Professor Gervais,[23] the opossums were represented in France by no less than eight species.

Early Man in Britain and His Place in the Tertiary Period - Fig. 5.—Upper Eocene Mammalia.png

UPPER EOCENE

Anoplotherium.Lemuroid.
Palæotherium.Xiphodon.

Fig. 5.—Upper Eocene Mammalia.

The birds which lived on and around the upper Eocene lake of Paris consist of ten species, among which some are closely allied to the buzzard, woodcock, quail, pelican, ibis, flamingo, and hornbill of Africa.[24]

The Order Primates represented.

The upper Eocene forests of France were also haunted by representatives of the highest order of mammalia, or the Primates, which includes the families of man, the ape, and the lemur. The Adapis[25] of the Paris basin classified by Cuvier with the Anoplotheres, has recently been proved to be related to the last of these as well as to the hoofed quadrupeds and insectivores. To the same family also belong the Necrolemur,[26] discovered in the south of France, and the Cænopithecus[27] of Rütimeyer, found in Switzerland. The family is also proved[28] by Marsh and Cope to have inhabited the forests of North America, during the whole of the Eocene age in New Mexico, Wyoming, in Dakotah and Nebraska. None of these are identical with any living genus of lemur, but all possess characters bringing them into relation with one or other of the families of hoofed quadrupeds living in the Eocene period (see Fig. 5).[29]

The Climate of Britain Tropical.

The climate of Britain is proved to have been tropical from the time of the London Clay down to the close of the Eocene period by the concurrent testimony of the flora and of the fauna. Just as a high temperature is necessary for the well-being of the feather-palms (see Fig. 4) and large fan-palms, so is it necessary for the full development of the larger forms of reptilian life, such as the alligator, crocodile, and gavial. Among living mammals, the tapir, the inhabitant of the warmer regions of Asia and America, is the closest representative of a large section of the Eocene mammalia, and the lemurs of the present day are only found in hot climates. The nautilus, larger volutes, cowries, and other shells, so common in the Eocene strata, are now only to be met with in the tropical and sub-tropical seas.[30] Mr. Starkie Gardner estimates the mean annual temperature of Britain in the mid Eocene age at 70°, from the examination of the fossil plants.

General Conclusions.

It is impossible for the reader who has followed these three stages of the Eocene period not to be impressed with the extraordinary character of the mammalia. They stand in the same relation to living species that the main branches of a tree bear to the branchlets and leaves. Only one living genus was then known in Europe, and that is a representative of the marsupial type, which, so far as we know, was universal in Europe in the Secondary period. Marsupial characters, however, are to be met with in the Eocene beasts of prey, which render it very probable that in those times the carnivores were in the act, so to speak, of departing from the type of their marsupial ancestry. On no other hypothesis but that of lineal descent is it possible to account for such characters as their small marsupial brain, their dentition, and numerous details in their skeletons. It would further appear that the lemurs of those times were closely linked to the Ungulata or hoofed quadrupeds.

Man not here.

It is obvious that man had no place in such an assemblage of animals as that described in this chapter. To seek for highly-specialised man in a fauna where no living genus of placental mammal was present would be an idle and hopeless quest. Nevertheless, it is an important fact to note that the lowest member of the order Primates, to which he belongs in natural history classification, was represented in the upper Eocenes of Europe, and throughout the whole of the Eocene period in America.

  1. Chapter V. of this work; Cave-hunting, 110.
  2. Lyell, Principles, 131.
  3. According to Gervais it belongs to an extinct genus Peratherium (Zool. et Pal. Franc., 4to), In this chapter, however, the views of Gaudry are followed (Les Enchainements du Monde Animal).
  4. For a systematic account of the Eocene strata, see Lyell, Student's Elements, c. xvi.
  5. "Physical Geography of the Tertiary Estuary of the Isle of Wight," by H. C. Sorby, Esq. Edinb. New Phil. Jour. N.S. April 1857.
  6. Owen, Palæontology, p. 281.
  7. Hooker, Proceed. Royal Soc. xxviii. p. 51. Saporta, Les Anciens Climats de l'Europe et le Developpement de la Végétation. Association Française, Havre, 1877. Dawson, Princetown Rev. 1879, p. 182.
  8. Nature xx. 12.
  9. If the fossil floras of the Polar regions be judged from the stand- point offered by the decrease of temperature from the equator towards the pole, they are Eocene. If, however, we look at them, homotaxially, from the point of view offered by the European Meiocenes, they are Meiocene. Mr. Starkie Gardner takes the former, Dr. Heer the latter, view. See Starkie Gardner, Nature, xix. 124; xx. 10.
  10. This map was drawn in 1875, and its accuracy is confirmed by the independent reasoning of Mr. Starkie Gardner.
  11. H. Mohn, Nature, vi. p. 526.
  12. Ramsay, Physical Geology and Geography of Great Britain, 3d edit, p 213.
  13. Bowerbank, Hist. Fossil Fruits and Seeds of London Clay, 1840. Heer, Climat et Végétation du Pays Tertiaire, transl. Gaudin, 4to, p. 172. For a further account of the Lower Eocene flora, the reader may be referred to a forthcoming work by Messrs. Starkie Gardner and Ettingshausen, in the Palæontographical Society's publications.
  14. Owen, Brit. Foss. Mammals, and Palæontology. Gervais, Zoologie et Paléontologie Française, 1859. In determining the principal mammalia in each of the Eocene faunas I have used the works of Owen, Gervais, and Gaudry, as well as a list of the Eocene mammals in the British Museum which has been prepared for me by the kindness of Mr. W. Davies, and my own notes of the species in the Woodwardian Museum at Cambridge. For systematic lists, see Appendix I.
  15. Gervais, Zool. et Pal. Franc. Gaudry, Les Enchainements du Monde Animal.
  16. The discoveries made in New Mexico, Wyoming, and Utah, by Professor Marsh and others, prove that the Coryphodon was an inhabitant of America, and that the animal was a five-toed tapiroid animal possessed of all the characters of the sub-order Perissodactyla. See Marsh, Amer. Jour. Sc. and Arts, xiv. July 1877.
  17. Owen, Trans. Zool. Soc., vii. p. 146. Palæontology, p. 291. Quart. Geol. Journ. Lond., xxix. p. 511.
  18. Milne Edwards, Recherches sur les Oiseaux Fossiles, 4to.
  19. Owen, Palæontology, p. 291.
  20. J. S. Gardner.—"Tropical Forests of Hampshire," Nature, xv. pp. 229, 258, 279. Alum Bay: De La Harpe. Geology of Isle of Wight. Memoirs of the Geological Survey of Great Britain, pp. 41, 109.
  21. Gervais, Zool. et Pal, Franç. p. 327. In this view of the French mid Eocene mammalia, I have followed Gervais rather than Gaudry.
  22. American Addresses, Lecture III.
  23. Zool. et Paléont. p. 334.
  24. Milne Edwards, Oiseaux Fossiles, ii. 543.
  25. Gervais, Zool. et Paléontologie Generale, p. 28 et seq. Journ. de Zool. i. 476. Phosphorites de Quercy, Tarn-et-Garonne-et-Lot.
  26. Filhol, Journ. de Zool. ii. 476. Gaudry, op. cit. iv. 521. Dell fortrie, op. cit. ii. 414. Gaudry, Les Enchainements, c. x.
  27. Rütimeyer, Ueber die Herkunft Unserer Thierwelt, 4to, 1867, p. 52. The fauna of the Bohnerze, in which the Cænopithecus was found, is considered by Heer to be of Mid Eocene age. It seems to me more probable that it represents also the Upper and Lower divisions. The local deposit of Bohnerze (iron ore) in Switzerland had begun in the Cretaceous age, and may have been continued throughout the Eocene period. The fauna contains characteristic forms of upper as well as Middle Eocene species.
  28. Marsh, Introduction and Succession of Vertebrate Life in America. American Association for the Advancement of Science, 1877. Cope, Hyopsodus. Report of U.S. Geological Survey of the Territories. Fossil Vertebrates, i. 75.
  29. In Fig. 5 I have chosen the Galago as the representative of the Eocene lemurs.
  30. Nature, xix. p. 125.