endure the climate of Europe. In the fossil specimens the same glands or protuberances are preserved (see Figure 134) as those which are seen in the axils of the primary veins of the leaves in the recent Til. (Contributions a la Flore fossile Italienne. Gaudin and Strozzi. Plate 11 Figure 3. Gaudin page 22.) Another plant also indicating a warmer climate is the Liquidambar europaeum, Brong. (see Figure 135), a species nearly allied to L. styracifluum, L., which flourishes in most places in the Southern States of North America, on the borders of the Gulf of Mexico.
CHAPTER XIV.
MIOCENE PERIOD.– UPPER MIOCENE.
Upper Miocene Strata of France.– faluns of Touraine. Tropical Climate implied by Testacea.
Proportion of recent Species of Shells. faluns more ancient than the Suffolk Crag. Upper Miocene of Bordeaux and the South of France. Upper Miocene of Oeningen, in Switzerland. Plants of the Upper Fresh-water Molasse. Fossil Fruit and Flowers as well as Leaves. Insects of the Upper Molasse.
Middle or Marine Molasse of Switzerland. Upper Miocene Beds of the Bolderberg, in Belgium. Vienna Basin.
Upper Miocene of Italy and Greece.
Upper Miocene of India; Siwalik Hills. Older Pliocene and Miocene of the United States.
UPPER MIOCENE STRATA OF FRANCE.– FALUNS OF TOURAINE.
The strata which we meet with next in the descending order are those called by many geologists “Middle Tertiary,” for which in 1833 I proposed the name of Miocene, selecting the “faluns” of the valley of the Loire, in France, as my example or type. I shall now call these falunian deposits Upper Miocene, to distinguish them from others to which the name of Lower Miocene will be given.
No British strata have a distinct claim to be regarded as Upper Miocene, and as the Lower Miocene are also but feebly represented in the British Isles, we must refer to foreign examples in illustration of this important period in the earth’s history. The term “faluns” is given provincially by French agriculturists to shelly sand and marl spread over the land in Touraine, just as similar shelly deposits were formerly much used in Suffolk to fertilise the soil, before the coprolitic or phosphatic nodules came into use. Isolated masses of such faluns occur from near the mouth of the Loire, in the neighbourhood of Nantes, to as far inland as a district south of Tours. They are also found at Pontlevoy, on the Cher, about seventy miles above the junction of that river with the Loire, and thirty miles south-east of Tours. Deposits of the same age also appear under new mineral conditions near the towns of Dinan and Rennes, in Brittany. I have visited all the localities above enumerated, and found the beds on the Loire to consist principally of sand and marl, in which are shells and corals, some entire, some rolled, and others in minute fragments. In certain districts, as at Doue, in the Department of Maine and Loire, ten miles south- west of Saumur, they form a soft building-stone, chiefly composed of an aggregate of broken shells, bryozoa, corals, and echinoderms, united by a calcareous cement; the whole mass being very like the Coralline Crag near Aldborough, and Sudbourn in Suffolk. The scattered patches of faluns are of slight thickness, rarely exceeding fifty feet; and between the district called Sologne and the sea they repose on a great variety of older rocks; being seen to rest successively upon gneiss, clay-slate, various secondary formations, including the chalk; and, lastly, upon the upper fresh-water limestone of the Parisian tertiary series, which, as before mentioned (Chapter 9), stretches continuously from the basin of the Seine to that of the Loire.
(FIGURE 136. Dinotherium giganteum, Kaup.)
At some points, as at Louans, south of Tours, the shells are stained of a ferruginous colour, not unlike that of the Red Crag of Suffolk. The species are, for the most part, marine, but a few of them belong to land and fluviatile genera. Among the former, Helix turonensis (Figure 38, Chapter 3) is the most abundant. Remains of terrestrial quadrupeds are here and there intermixed, belonging to the genera Dinotherium (Figure 136), Mastodon, Rhinoceros, Hippopotamus, Chaeropotamus, Dichobune, Deer, and others, and these are accompanied by cetacea, such as the Lamantin, Morse, Sea-calf, and Dolphin, all of extinct species.
The fossil testacea of the faluns of the Loire imply, according to the late Edward Forbes, that the beds were formed partly on the shore itself at the level of low water, and partly at very moderate depths, not exceeding ten fathoms below that level. The molluscan fauna is, on the whole, much more littoral than that of the Pliocene Red and Coralline Crag of Suffolk, and implies a shallower sea. It is, moreover, contrasted with the Suffolk Crag by the indications it affords of an extra-European climate. Thus it contains seven species of Cypraea, some larger than any existing cowry of the Mediterranean, several species of Oliva, Ancillaria, Mitra, Terebra, Pyrula, Fasciolaria, and Conus. Of the cones there are no less than eight species, some very large, whereas the only European cone now living is of diminutive size. The genus Nerita, and many others, are also represented by individuals of a type now characteristic of equatorial seas, and wholly unlike any Mediterranean forms. These proofs of a more elevated temperature seem to imply the higher antiquity of the faluns as compared with the Suffolk Crag, and are in perfect accordance with the fact of the smaller proportion of testacea of recent species found in the faluns.
Out of 290 species of shells, collected by myself in 1840 at Pontlevoy, Louans, Bossee, and other villages twenty miles south of Tours, and at Savigne, about fifteen miles north-west of that place, seventy-two only could be identified with recent species, which is in the proportion of twenty-five per cent. A large number of the 290 species are common to all the localities, those peculiar to each not being more numerous than we might expect to find in different bays of the same sea.
The total number of species of testaceous mollusca from the faluns in my possession is 302, of which forty-five only, or fourteen per cent, were found by Mr. Wood to be common to the Suffolk Crag. The number of corals, including bryozoa and zoantharia, obtained by me at Doue and other localities before adverted to, amounts to forty-three, as determined by Mr. Lonsdale, of which seven (one of them a zoantharian) agree specifically with those of the Suffolk Crag. Some of the genera occurring fossil in Touraine, as the corals Astrea and Dendrophyllia, and the bryozoan Lunulites, have not been found in European seas north of the Mediterranean; nevertheless, the zoantharia of the faluns do not seem to indicate, on the whole, so warm a climate as would be inferred from the shells.
It was stated that, on comparing about 300 species of Touraine shells with about 450 from the Suffolk Crag, forty-five only were found to be common to both, which is in the proportion of only fifteen per cent. The same small amount of agreement is found in the corals also. I formerly endeavoured to reconcile this marked difference in species with the supposed co-existence of the two faunas, by imagining them to have severally belonged to distinct zoological provinces or two seas, the one opening to the north and the other to the south, with a barrier of land between them, like the Isthmus of Suez, now separating the Red Sea and the Mediterranean. But I now abandon that idea for several reasons; among others, because I succeeded in 1841 in tracing the Crag fauna southward in Normandy to within seventy miles of the Falunian type, near Dinan, yet found that both assemblages of fossils retained their distinctive characters, showing no signs of any blending of species or transition of climate.
The principal grounds, however, for referring the English Crag to the older Pliocene and the French faluns to the Upper Miocene epochs, consist in the predominance of fossil shells in the British strata identifiable with species not only still living, but which are now inhabitants of neighbouring seas, while the accompanying extinct species are of genera such as characterise Europe. In the faluns, on the contrary, the recent species are in a decided minority; and most of them are now inhabitants of the Mediterranean, the coast of Africa, and the Indian Ocean; in a word, less northern in character, and pointing to the prevalence of a warmer climate. They indicate a state of things receding farther from the present condition of Central Europe in physical geography and climate, and doubtless, therefore, receding farther from our era in time.
(FIGURE 137. Voluta Lamberti, Sowerby. Variety characteristic of Faluns of Touraine. Miocene.)
Among the conspicuous fossils common to the faluns of the Loire and the Suffolk Crag is a variety of the Voluta Lamberti, a shell already alluded to (Figure 123). The specimens of this shell which I have myself collected in Touraine, or have seen in museums, are thicker and heavier than British individuals of the same species, and shorter in proportion to their width, and have the folds on the columella less oblique, as represented in Figure 137.
UPPER MIOCENE OF BORDEAUX AND THE SOUTH OF FRANCE.
A great extent of country between the Pyrenees and the Gironde is overspread by tertiary deposits of various ages, and chiefly of Miocene date. Some of these, near Bordeaux, coincide in age with the faluns of Touraine, already mentioned, but many of the species of shells are peculiar to the south. The succession of beds in the basin of the Gironde implies several oscillations of level by which the same wide area was alternately converted into sea and land and into brackish-water lagoons, and finally into fresh-water ponds and lakes.
Among the fresh-water strata of this age near the base of the Pyrenees are marls, limestones and sands, in which the eminent comparative anatomist, M. Lartet, has obtained a great number of fossil mammalia common to the faluns of the Loire and the Upper Miocene beds of Switzerland, such as Dinotherium giganteum and Mastodon angustidens; also the bones of quadrumana, or of the ape and monkey tribe, which were discovered in 1837, the first of that order of quadrupeds detected in Europe. They were found near Auch, in the Department of Gers, in latitude 43 degrees 39′ N. About forty miles west of Toulouse. They were referred by MM. Lartet and Blainville to a genus closely allied to the Gibbon, to which they gave the name of Pliopithecus. Subsequently, in 1856, M. Lartet described another species of the same family of long-armed apes (Hylobates), which he obtained from strata of the same age at Saint-Gaudens, in the Haute Garonne. The fossil remains of this animal consisted of a portion of a lower jaw with teeth and the shaft of a humerus. It is supposed to have been a tree-climbing frugivorous ape, equalling man in stature. As the trunks of oaks are common in the lignite beds in which it lay, it has received the generic name of Dryopithecus. The angle formed by the ascending ramus of the jaw and the alveolar border is less open, and therefore more like the human subject, than in the Chimpanzee, and what is still more remarkable, the fossil, a young but adult individual, had all its milk teeth replaced by the second set, while its last true molar (or wisdom-tooth) was still undeveloped, or only existed as a germ in the jaw-bone. In the mode, therefore, of the succession of its teeth (which, as in all the old-World apes, exactly agree in number with those in man) it differed from the Gorilla and Chimpanzee, and corresponded with the human species.
UPPER MIOCENE BEDS OF OENINGEN, IN SWITZERLAND.
The faluns of the Loire first served, as already stated, as the type of the Miocene formations in Europe. They yielded a plentiful harvest of marine fossil shells and corals, but were entirely barren of plants and insects. In Switzerland, on the other hand, deposits of the same age have been discovered, remarkable for their botanical and entomological treasures. We are indebted to Professor Heer, of Zurich, for the description, restoration, and classification of several hundred species and varieties of these fossil plants, the whole of which he has illustrated by excellent figures in his “Flora Tertiaria Helvetiae.” This great work, and those of Adolphe Brongniart, Unger, Goppert and others, show that this class of fossils is beginning to play the same important part in the classification of the tertiary strata containing lignite or brown coal as an older flora has long played in enabling us to understand the ancient coal or carboniferous formation. No small skepticism has always prevailed among botanists as to whether the leaves alone and the wood of plants could ever afford sufficient data for determining even genera and families in the vegetable kingdom. In truth, before such remains could be rendered available a new science had to be created. It was necessary to study the outlines, nervation, and microscopic structure of the leaves, with a degree of care which had never been called for in the classification of living plants, where the flower and fruit afforded characters so much more definite and satisfactory. As geologists, we can not be too grateful to those who, instead of despairing when so difficult a task was presented to them, or being discouraged when men of the highest scientific attainments treated the fossil leaves as worthless, entered with full faith and enthusiasm into this new and unexplored field. That they should frequently have fallen into errors was unavoidable, but it is remarkable, especially if we inquire into the history of Professor Heer’s researches, how often early conjectures as to the genus and family founded on the leaves alone were afterwards confirmed when fuller information was obtained. As examples to be found on comparing Heer’s earlier and later works, I may instance the chestnut, elm, maple, cinnamon, magnolia, buckbean or Menyanthes, vine, buckthorn (Rhamnus), Andromeda and Myrica, and among the conifers Sequoia and Taxodium. In all these cases the plants were first recognised by their leaves, and the accuracy of the determination was afterwards confirmed when the fruit, and in some instances both fruit and flower, were found attached to the same stem as the leaves.
But let us suppose that no fruit, seed, or flower had ever been met with in a fossil state, we should still have been indebted to the persevering labours of botanical palaeontologists for one of the grandest scientific discoveries for which the present century is remarkable– namely, the proofs now established of the prevalence of a mild climate and a rich arborescent flora in the arctic regions in that Miocene epoch on the history of which we are now entering. It may be useful if I endeavour to give the reader in a few words some idea of the nature of the evidence of these important conclusions, to show how far they may be safely based on fossil leaves alone. When we begin by studying the fossils of the Newer Pliocene deposits, such as those of the Upper Val d’Arno, before alluded to, we perceive that the fossil foliage agrees almost entirely with the trees and shrubs of a modern European forest. In the plants of the Older Pliocene strata of the same region we observe a larger proportion of species and genera which, although they may agree with well-known Asiatic or other foreign types, are at present wanting in Italy. If we then examine the Miocene formations of the same country, exotic forms become more abundant, especially the palms, whether they belong to the European or American fan-palms, Chamaerops and Sabal, or to the more tropical family of the date-palms or Phoenicites, which last are conspicuous in the Lower Miocene beds of Central Europe. Although we have not found the fruit or flower of these palms in a fossil state, the leaves are so characteristic that no one doubts the family to which they belong, or hesitates to accept them as indications of a warm and sub-tropical climate.
When the Miocene formations are traced to the northward of the 50th degree of latitude, the fossil palms fail us, but the greater proportion of the leaves, whether identical with those of existing European trees or of forms now unknown in Europe, which had accompanied the Miocene palms, still continue to characterise rocks of the same age, until we meet with them not only in Iceland, but in Greenland, in latitude 70 degrees N., and in Spitzbergen, latitude 78 degrees 56′, or within about 11 degrees of the pole, and under circumstances which clearly show them to have been indigenous in those regions, and not to have been drifted from the south (see Chapter 15). Not only, therefore, has the botanist afforded the geologist much palaeontological assistance in identifying distinct tertiary formations in distant places by his power of accurately discriminating the forms, veining, and microscopic structure of leaves or wood, but, independently of that exact knowledge derivable from the organs of fructification, we are indebted to him for one of the most novel, unexpected results of modern scientific inquiry.
The Miocene formations of Switzerland have been called MOLASSE, a term derived from the French MOL, and applied to a SOFT, incoherent, greenish sandstone, occupying the country between the Alps and the Jura. This molasse comprises three divisions, of which the middle one is marine, and being closely related by its shells to the faluns of Touraine, may be classed as Upper Miocene. The two others are fresh-water, the upper of which may be also grouped with the faluns, while the lower must be referred to the Lower Miocene, as defined in the next chapter.
UPPER FRESH-WATER MOLASSE.
This formation is best seen at Oeningen, in the valley of the Rhine, between Constance and Schaffhausen, a locality celebrated for having produced in the year 1700 the supposed human skeleton called by Scheuchzer “homo diluvii testis,” a fossil afterwards demonstrated by Cuvier to be a reptile, or aquatic salamander, of larger dimensions than even its great living representative, the salamander of Japan.
The Oeningen strata consist of a series of marls and limestones, many of them thinly laminated, and which appear to have slowly accumulated in a lake probably fed by springs holding carbonate of lime in solution. The elliptical area over which this fresh-water formation has been traced extends, according to Sir Roderick Murchison, for a distance of ten miles east and west from Berlingen, on the right bank of the river to Wangen, and to Oeningen, near Stein, on the left bank. The organic remains have been chiefly derived from two quarries, the lower of which is about 550 feet above the level of the Lake of Constance, while the upper quarry is 150 feet higher. In this last, a section thirty feet deep displays a great succession of beds, most of them splitting into slabs and some into very thin laminae. Twenty-one beds are enumerated by Professor Heer, the uppermost a bluish-grey marl seven feet thick, with organic remains, resting on a limestone with fossil plants, including leaves of poplar, cinnamon, and pond- weed (Potamogeton), together with some insects; while in the bed No. 4, below, is a bituminous rock, in which the Mastodon tapiroides, a characteristic Upper Miocene quadruped, has been met with. The 5th bed, two or three inches thick, contains fossil fish, e.g., Leuciscus (roach), and the larvae of dragon-flies, with plants such as the elm (Ulmus), and the aquatic Chara. Below this are other plant-beds; and then, in No. 9, the stone in which the great salamander (Andrias Scheuchzeri) and some fish were found. Below this other strata occur with fish, tortoises, the great salamander before alluded to, fresh-water mussels, and plants. In No. 16 the fossil fox of Oeningen, galecynus Oeningensis, Owen, was obtained by Sir R. Murchison. To this succeed other beds with mammalia (Lagomys), reptiles, (Emys), fish, and plants, such as walnut, maple, and poplar. In the 19th bed are numerous fish, insects, and plants, below which are marls of a blue indigo colour.
In the lower quarry eleven beds are mentioned, in which, as in the upper, both land and fresh-water plants and many insects occur. In the 6th, reckoning from the top, many plants have been obtained, such as Liquidambar, Daphnogene, Podogonium, and Ulmus, together with tortoises, besides the bones and teeth of a ruminant quadruped, named by H. von Meyer Palaeomeryx eminens. No. 9 is called the insect-bed, a layer only a few inches thick, which, when exposed to the frost, splits into leaves as thin as paper. In these thin laminae plants such as Liquidambar, Daphnogene, and Glyptostrobus, occur, with innumerable insects in a wonderful state of preservation, usually found singly. Below this is an indigo- blue marl, like that at the bottom of the higher quarry, resting on yellow marl ascertained to be at least thirty feet thick.
(FIGURE 138. Cinnamomum polymorphum, Ad. Brong. Upper and Lower Miocene. a. Leaf.
b. Flower, natural size; Heer Plate 93 Figure 28. c. Ripe fruit of Cinnamomum polymorphum, from Oeningen; Heer, Plate 94 Figure 14.
d. Fruit of recent Cinnamomum camphorum of Japan; Heer, Plate 152 Figure 18.)
All the above fossil-bearing strata were evidently formed with extreme slowness. Although the fossiliferous beds are, in the aggregate, no more than a few yards in thickness, and have only been examined in the small area comprised in the two quarries just alluded to, they give us an insight into the state of animal and vegetable life in part of the Upper Miocene period, such as no other region in the world has elsewhere supplied. In the year 1859, Professor Heer had already determined no less than 475 species of plants and more than 800 insects from these Oeningen beds. He supposes that a river entering a lake floated into it some of the leaves and land insects, together with the carcasses of quadrupeds, among others a great Mastodon. Occasionally, during tempests, twigs and even boughs of trees with their leaves were torn off and carried for some distance so as to reach the lake. Springs, containing carbonate of lime, seem at some points to have supplied calcareous matter in solution, giving origin locally to a kind of travertin, in which organic bodies sinking to the bottom became hermetically sealed up. The laminae, says Heer, which immediately succeed each other were not all formed at the same season, for it can be shown that, when some of them originated, certain plants were in flower, whereas, when the next of these layers was produced, the same plants had ripened their fruit. This inference is confirmed by independent proofs derived from insects. The principal insect-bed is rarely two inches thick, and is composed, says Heer, of about 250 leaf-like laminae, some of which were deposited in the spring, when the Cinnamomum polymorphum (Figure 138) was in flower, others in summer, when winged ants were numerous, and when the poplar and willow had matured their seed; others, again, in autumn, when the same Cinnamomum polymorphum (Figure 138) was in fruit, as well as the liquidambar, oak, clematis, and many other plants. The ancient lake seems to have had a belt of poplars and willows round its borders, countless leaves of which were imbedded in mud, and together with them, at some points, a species of reed, Arundo, which was very common.
One of the most characteristic shrubs is a papilionaceous and leguminous plant of an extinct genus, called by Heer Podogonium, of which two species are known. Entire twigs have been found with flowers, and always without leaves, as the flowers evidently came out, as in the poplar and willow tribe, before any leaves made their appearance. Other specimens have been obtained with ripe fruits accompanied by leaves, which resemble those of the tamarind, to which it was evidently allied, being of the family Caesalpineae, now proper to warmer regions.
(FIGURE 139. Acer trilobatum, normal form; Heer, Flora Tert. Helv. Plate 114 Figure 2. Size 1/2 diam. (Part only of the long stalk of the original fossil specimen is here given ). Upper Miocene, Oeningen; also found in Lower Miocene of Switzerland.)
(FIGURE 140. Acer trilobatum.
a. Abnormal variety of leaf; Heer, Plate 110 Figure 16. b. Flower and bracts, normal form; Heer, Plate 111 Figure 21. c. Half a seed-vessel; Heer, Plate 111 Figure 5.)
(FIGURE 141. Platanus aceroides, Gopp.; Heer, Plate 88 Figures 5-8. Size 2/3 diam. Upper Miocene, Oeningen.
a. Leaf.
b. The core of a bundle of pericarps. c. Single fruit or pericarp, natural size.)
The Upper Miocene flora of Oeningen is peculiarly important, in consequence of the number of genera of which not merely the leaves, but, as in the case of the Podogonium just mentioned, the fruit also and even the flower are known. Thus there are nineteen species of maple, ten of which have already been found with fruit. Although in no one region of the globe do so many maples now flourish, we need not suspect Professor Heer of having made too many species in this genus when we consider the manner in which he has dealt with one of them, Acer trilobatum, Figures 139 and 140. Of this plant the number of marked varieties figured and named is very great, and no less than three of them had been considered as distinct species by other botanists, while six of the others might have laid claim, with nearly equal propriety, to a like distinction. The common form, called Acer trilobatum, Figure 139, may be taken as a normal representative of the Oeningen fossil, and Figure 140, as one of the most divergent varieties, having almost four lobes in the leaf instead of three.
(FIGURE 142. Smilax sagittifera; Heer, Plate 30 Figure 7. Size 1/2 diameter. a. Leaf.
b. Flower magnified, one of the six petals wanting at d. Upper Miocene, Oeningen.
c. Smilax obtusifolia; Heer, Plate 30 Figure 9; natural size. Upper Miocene, Oeningen.)
(FIGURE 143. Fruit of the fossil and recent species of Hakea, a genus of Proteaceae.
a. Leaf of fossil species, Hakea salicina. Upper Miocene, Oeningen; Heer Plate 97 Figure 29. 1/3 diameter.
b. Impression of woody fruit of same, showing thick stalk. 2/3 diameter. c. Seed of same, natural size.
d. Fruit of living Australian species, Hakea saligna, R. Brown. 1/2 diameter. e. Seed of same, natural size.)
Among the conspicuous genera which abounded in the Miocene period in Europe is the plane-tree, Platanus, the fossil species being considered by Heer to come nearer to the American P. occidentalis than to P. orientalis of Greece and Asia Minor. In some of the fossil specimens the male flowers are preserved. Among other points of resemblance with the living plane-trees, as we see them in the parks and squares of London, fossil fragments of the trunk are met with, having pieces of their bark peeling off.
The vine of Oeningen, Vitis teutonica, Ad. Brong, is of a North American type. Both the leaves and seeds have been found at Oeningen, and bunches of compressed grapes of the same species have been met with in the brown coal of Wetteravia in Germany. No less than eight species of smilax, a monocotyledonous genus, occur at Oeningen and in other Upper Miocene localities, the flowers of some of them, as well as the leaves, being preserved; as in the case of the very common fossil, S. sagittifera, Figure 142, a.
Leaves of plants supposed to belong to the order Proteaceae have been obtained partly from Oeningen and partly from the lacustrine formation of the same age at Locle in the Jura. They have been referred to the genera Banksia, Grevillea, Hakea, and Persoonia. Of Hakea there is the impression of a supposed seed- vessel, with its characteristic thick stalk and seeds, but as the fruit is without structure, and has not yet been found attached to the same stem as the leaf, the proof is incomplete.
To whatever family the foliage hitherto regarded as proteaceous by many able palaeontologists may eventually be shown to belong, we must be careful not to question their affinity to that order of plants on those geographical considerations which have influenced some botanists. The nearest living Proteaceae now feel the in Abyssinia in latitude 20 degrees N., but the greatest number are confined to the Cape and Australia. The ancestors, however, of the Oeningen fossils ought not to be looked for in such distant regions, but from that European land which in Lower Miocene times bore trees with similar foliage, and these had doubtless an Eocene source, for cones admitted by all botanists to be proteaceous have been met with in one division of that older Tertiary group (see Figure 206 Chapter 16). The source of these last, again, must not be sought in the antipodes, for in the white chalk of Aix-la-Chapelle leaves like those of Grevillea and other proteaceous genera have been found in abundance, and, as we shall see in Chapter 17, in a most perfect state of preservation. All geologists agree that the distribution of the Cretaceous land and sea had scarcely any connection with the present geography of the globe.
(FIGURE 144. Glyptostrobus Europaeus. Branch with ripe fruit; Heer, Plate 20 Figure 1. Upper Miocene, Oeningen.)
In the same beds with the supposed Proteaceae there occurs at Locle a fan-palm of the American type Sabal (for genus see Figure 151), a genus which ranges throughout the low country near the sea from the Carolinas to Florida and Louisiana. Among the Coniferae of Upper Miocene age is found a deciduous cypress nearly allied to the Taxodium distichum of North America, and a Glyptostrobus (Figure 144), very like the Japanese G. heterophyllus, now common in our shrubberies.
Before the appearance of Heer’s work on the Miocene Flora of Switzerland, Unger and Goppert had already pointed out the large proportion of living North American genera which distinguished the vegetation of the Miocene period in Central Europe. Next in number, says Heer, to these American forms at Oeningen the European genera preponderate, the Asiatic ranking in the third, the African in the fourth, and the Australian in the fifth degree. The American forms are more numerous than in the Italian Pliocene flora, and the whole vegetation indicates a warmer climate than the Pliocene, though not so high a temperature as that of the older or Lower Miocene period.
The conclusions drawn from the insects are for the most part in perfect harmony with those derived from the plants, but they have a somewhat less tropical and less American aspect, the South European types being more numerous. On the whole, the insect fauna is richer than that now inhabiting any part of Europe. No less than 844 species are reckoned by Heer from the Oeningen beds alone, the number of specimens which he has examined being 5080. The entire list of Swiss species from the Upper and Lower Miocene together amount to 1322. Almost all the living families of Coleoptera are represented, but, as we might have anticipated from the preponderance of arborescent and ligneous plants, the wood-eating beetles play the most conspicuous part, the Buprestidae and other long-horned beetles being particularly abundant.
(FIGURE 145. Harpactor maculipes, Heer. Upper Miocene, Oeningen.)
The patterns and some remains of the colours both of Coleoptera and Hemiptera are preserved at Oeningen, as, for example in Harpactor (Figure 145), in which the antennae, one of the eyes, and the legs and wings are retained. The characters, indeed, of many of the insects are so well defined as to incline us to believe that if this class of the invertebrata were not so rare and local, they might be more useful than even the plants and shells in settling chronological points in geology.
MIDDLE OR MARINE MOLASSE (UPPER MIOCENE) OF SWITZERLAND.
It was before stated that the Miocene formation of Switzerland consisted of, first, the upper fresh-water molasse, comprising the lacustrine marls of Oeningen; secondly, the marine molasse, corresponding in age to the faluns of Touraine; and thirdly, the lower fresh-water molasse. Some of the beds of the marine or middle series reach a height of 2470 feet above the sea. A large number of the shells are common to the faluns of Touraine, the Vienna basin, and other Upper Miocene localities. The terrestrial plants play a subordinate part in the fossiliferous beds, yet more than ninety of them are enumerated by Heer as belonging to this falunian division, and of these more than half are common to subjacent Lower Miocene beds, while a proportion of about forty-five in one hundred are common to the overlying Oeningen flora. Twenty-six of the ninety-two species are peculiar.
UPPER MIOCENE OF THE BOLDERBERG, IN BELGIUM.
(FIGURE 146. Oliva Dufresnii, Bast. Bolderberg, Belgium; natural size. a. Front view.
b. Back view.)
In a small hill or ridge called the Bolderberg, which I visited in 1851, situated near Hasselt, about forty miles E.N.E. of Brussels, strata of sand and gravel occur, to which M. Dumont first called attention as appearing to constitute a northern representative of the faluns of Touraine. On the whole, they are very distinct in their fossils from the two upper divisions of the Antwerp Crag before mentioned (Chapter 13), and contain shells of the genera Oliva, Conus, Ancillaria, Pleurotoma, and Cancellaria in abundance. The most common shell is an Olive (Figure 146), called by Nyst Oliva Dufresnii; and constituting, as M. Bosquet observes, a smaller and shorter variety of the Bordeaux species.
So far as the shells of the Bolderberg are known, the proportion of recent species agrees with that in the faluns of Touraine, and the climate must have been warmer than that of the Coralline Crag of England.
UPPER MIOCENE BEDS OF THE VIENNA BASIN.
In South Germany the general resemblance of the shells of the Vienna tertiary basin with those of the faluns of Touraine has long been acknowledged. In the late Dr. Hornes’s excellent work on the fossil mollusca of that formation, we see accurate figures of many shells, clearly of the same species as those found in the falunian sands of Touraine.
According to Professor Suess, the most ancient and purely marine of the Miocene strata in this basin consist of sands, conglomerates, limestones, and clays, and they are inclined inward, or from the borders of the trough towards the centre, their outcropping edges rising much higher than the newer beds, whether Miocene or Pliocene, which overlie them, and which occupy a smaller area at an inferior elevation above the sea. M. Hornes has described no less than 500 species of gasteropods, of which he identifies one-fifth with living species of the Mediterranean, Indian, or African seas, but the proportion of existing species among the lamellibranchiate bivalves exceeds this average. Among many univalves agreeing with those of Africa on the eastern side of the Atlantic are Cypraea sanguinolenta, Buccinum lyratum, and Oliva flammulata. In the lowest marine beds of the Vienna basin the remains of several mammalia have been found, and among them a species of Dinotherium, a Mastodon of the Trilophodon family, a Rhinoceros (allied to R. megarhinus, Christol), also an animal of the hog tribe, Listriodon, von Meyer, and a carnivorous animal of the canine family. The Helix turonensis (Figure 38 Chapter 3), the most common land shell of the French faluns, accompanies the above land animals. In a higher member of the Vienna Miocene series are found Dinotherium giganteum (Figure 136 Chapter 14), Mastodon longirostris, Rhinoceros Schleiermacheri, Acerotherium incisivum, and Hippotherium gracile, all of them equally characteristic of an Upper Miocene deposit occurring at Eppelsheim, in Hesse Darmstadt; a locality also remarkable as having furnished in latitude 49 degrees 50 north the bone of a large ape of the Gibbon kind, the most northerly example yet discovered of a quadrumanous animal.
(FIGURE 147. Amphistegina Hauerina, d’Orbigny. Upper Miocene strata, Vienna.)
M. Alcide d’Orbigny has shown that the foraminifera of the Vienna basin differ alike from the Eocene and Pliocene species, and agree with those of the faluns, so far as the latter are known. Among the Vienna foraminifera, the genus Amphistegina (Figure 147) is very characteristic, and is supposed by d’Archiac to take the same place among the Rhizopods of the Upper Miocene era which the Nummulites occupy in the Eocene period.
The flora of the Vienna basin exhibits some species which have a general range through the whole Miocene period, such as Cinnamomum polymorphum (Figure 138 Chapter 14), and C. Scheuchzeri, also Planera Richardi, Mich., Liquidambar europaeum (Figure 135 Chapter 13) Juglans bilinica, Cassia ambigua, and C. lignitum. Among the plants common to the Upper Miocene beds of Oeningen, in Switzerland, are Platanus aceroides (Figure 141 Chapter 14), Myrica vindobonensis, and others.
UPPER MIOCENE STRATA OF ITALY.
We are indebted to Signor Michelotti for a valuable work on the Miocene shells of Northern Italy. Those found in the hill called the Superga, near Turin, have long been known to correspond in age with the faluns of Touraine, and they contain so many species common to the Upper Miocene strata of Bordeaux as to lead to the conclusion that there was a free communication between the northern part of the Mediterranean and the Bay of Biscay in the Upper Miocene period.
UPPER MIOCENE FORMATIONS OF GREECE.
At Pikerme, near Athens, MM. Wagner and Roth have described a deposit in which they found the remains of the genera Mastodon, Dinotherium, Hipparion, two species of Giraffe, Antelope, and others, some living and some extinct. With them were also associated fossil bones of the Semnopithecus, showing that here, as in the south of France, the quadrumana were characteristic of this period. The whole fauna attests the former extension of a vast expanse of grassy plains where we have now the broken and mountainous country of Greece; plains, which were probably united with Asia Minor, spreading over the area where the deep Aegean Sea and its numerous islands are now situated. We are indebted to M. Gaudry, who visited Pikerme, for a treatise on these fossil bones, showing how many data they contribute to the theory of a transition from the mammalia of the Upper Miocene through the Pliocene and Post-pliocene forms to those of living genera and species.
UPPER MIOCENE OF INDIA. SIWALIK HILLS.
The Siwalik Hills lie at the southern foot of the Himalayan chain, rising to the height of 2000 and 3000 feet. Between the Jumna and the Ganges they consist of inclined strata of sandstone, shingle, clay, and marl. We are indebted to the indefatigable researches of Dr. Falconer and Sir Proby Cautley, continued for fifteen years, for the discovery in these marls and sandstones of a great variety of fossil mammalia and reptiles, together with many fresh-water shells. Out of fifteen species of shells of the genera Paludina, Melania, Ampullaria, and Unio, all are extinct or unknown species with the exception of four, which are still inhabitants of Indian rivers. Such a proportion of living to extinct mollusca agrees well with the usual character of an Upper Miocene or Falunian fauna, as observed in Touraine, or in the basin of Vienna and elsewhere.
The genera of mammalia point in the same direction. One of them, of the genus Chalicotherium (or Anisodon of Lartet), is a pachyderm intermediate between the Rhinoceros and Anoplothere, and characteristic of the Upper Miocene strata of Eppelsheim, and of the south of France. With it occurs also an extinct form of Hippopotamus, called Hexaprotodon, and a species of Hippotherium and pig, also two species of Mastodon, two of elephant, and three other elephantine proboscidians; none of them agreeing with any fossil forms of Europe, and being intermediate between the genera Elephas and Mastodon, constituting the sub-genus Stegodon of Falconer. With these are associated a monkey, allied to the Semnopithecus entellus, now living in the Himalaya, and many ruminants. Among these last, besides the giraffe, camel, antelope, stag, and others, we find a remarkable new type, the Sivatherium, like a gigantic four-horned deer. There are also new forms of carnivora, both feline and canine, the Machairodus among the former, also hyaenas, and a subursine form called the Hyaenarctos, and a genus allied to the otter (Enhydriodon), of formidable size.
The giraffe, camel, and a large ostrich may be cited as proofs that there were formerly extensive plains where now a steep chain of hills, with deep ravines, runs for many hundred miles east and west. Among the accompanying reptiles are several crocodiles, some of huge dimensions, and one not distinguishable, says Dr. Falconer, from a species now living in the Ganges (C. Gangeticus); and there is still another saurian which the same anatomist has identified with a species now inhabiting India. There was also an extinct species of tortoise of gigantic proportions (Colossochelys Atlas), the curved shell of which was twelve feet three inches long and eight feet in diameter, the entire length of the animal being estimated at eighteen feet, and its probable height seven feet.
Numerous fossils of the Siwalik type have also been found in Perim Island, in the Gulf of Cambay, and among these a species of Dinotherium, a genus so characteristic of the Upper Miocene period in Europe.
OLDER PLIOCENE AND MIOCENE FORMATIONS IN THE UNITED STATES.
Between the Alleghany Mountains, formed of older rocks, and the Atlantic, there intervenes, in the United States, a low region occupied principally by beds of marl, clay, and sand, consisting of the cretaceous and tertiary formations, and chiefly of the latter. The general elevation of this plain bordering the Atlantic does not exceed 100 feet, although it is sometimes several hundred feet high. Its width in the middle and southern states is very commonly from 100 to 150 miles. It consists, in the South, as in Georgia, Alabama, and South Carolina, almost exclusively of Eocene deposits; but in North Carolina, Maryland, Virginia, Delaware, more modern strata predominate, of the age of the English Crag and faluns of Touraine. (Proceedings of the Geological Society volume 4 part 3 1845 page 547.)
(FIGURE 148. Fulgur canaliculatus. Maryland.)
(FIGURE 149. Fusus quadricostatus, Say. Maryland.)
In the Virginian sands, we find in great abundance a species of Astarte (A. undulata, Conrad), which resembles closely, and may possibly be a variety of, one of the commonest fossils of the Suffolk Crag (A. Omalii); the other shells also, of the genera Natica, Fissurella, Artemis, Lucina, Chama, Pectunculus, and Pecten, are analagous to shells both of the English Crag and French faluns, although the species are almost all distinct. Out of 147 of these American fossils I could only find thirteen species common to Europe, and these occur partly in the Suffolk Crag, and partly in the faluns of Touraine; but it is an important characteristic of the American group, that it not only contains many peculiar extinct forms, such as Fusus quadricostatus, Say (see Figure 149), and Venus tridacnoides, abundant in these same formations, but also some shells which, like Fulgur carica of Say and F. canaliculatus (see Figure 148), Calyptraea costata, Venus mercenaria, Lam., Modiola glandula, Totten, and Pecten magellanicus, Lam., are recent species, yet of forms now confined to the western side of the Atlantic– a fact implying that some traces of the beginning of the present geographical distribution of mollusca date back to a period as remote as that of the Miocene strata.
Of ten species of corals which I procured on the banks of the James River, one agrees generically with a coral now living on the coast of the United States. Mr. Lonsdale regarded these corals as indicating a temperature exceeding that of the Mediterranean, and the shells would lead to similar conclusions. Those occurring on the James River are in the 37th degree of N. latitude, while the French faluns are in the 47th; yet the forms of the American fossils would scarcely imply so warm a climate as must have prevailed in France when the Miocene strata of Touraine originated.
(FIGURE 150. Astrangia lineata, Lonsdale. Syn. Anthophyllum lineatum. Williamsburg, Virginia.)
Among the remains of fish in these post-eocene strata of the United States are several large teeth of the shark family, not distinguishable specifically from fossils of the faluns of Touraine.
CHAPTER XV.
LOWER MIOCENE (OLIGOCENE OF BEYRICH).
Lower Miocene Strata of France.
Line between Miocene and Eocene.
Lacustrine Strata of Auvergne.
Fossil mammalia of the Limagne d’Auvergne. Lower Molasse of Switzerland.
Dense Conglomerates and Proofs of Subsidence. Flora of the Lower Molasse.
American Character of the Flora.
Theory of a Miocene Atlantis.
Lower Miocene of Belgium.
Rupelian Clay of Hermsdorf near Berlin. Mayence Basin.
Lower Miocene of Croatia.
Oligocene Strata of Beyrich.
Lower Miocene of Italy.
Lower Miocene of England.
Hempstead Beds.
Bovey Tracey Lignites in Devonshire. Isle of Mull Leaf-Beds.
Arctic Miocene Flora.
Disco Island.
Lower Miocene of United States.
Fossils of Nebraska.
LINE BETWEEN MIOCENE AND EOCENE FORMATIONS.
The marine faluns of the valley of the Loire have been already described as resting in some places on a fresh-water tertiary limestone, fragments of which have been broken off and rolled on the shores and in the bed of the Miocene sea. Such pebbles are frequent at Pontlevoy on the Cher, with hollows drilled in them in which the perforating marine shells of the Falunian period still remain. Such a mode of superposition implies an interval of time between the origin of the fresh-water limestone and its submergence beneath the waters of the Upper Miocene sea. The limestone in question forms a part of the formation called the Calcaire de la Beauce, which constitutes a large table-land between the basins of the Loire and the Seine. It is associated with marls and other deposits, such as may have been formed in marshes and shallow lakes in the newest part of a great delta. Beds of flint, continuous or in nodules, accumulated in these lakes, and aquatic plants called Charae, left their stems and seed-vessels imbedded both in the marl and flint, together with fresh-water and land shells. Some of the siliceous rocks of this formation are used extensively for mill- stones. The flat summits or platforms of the hills round Paris, and large areas in the forest of Fontainebleau, as well as the Plateau de la Beauce, already alluded to, are chiefly composed of these fresh-water strata. Next to these in the descending order are marine sands and sandstone, commonly called the Gres de Fontainebleau, from which a considerable number of shells, very distinct from those of the faluns, have been obtained at Etampes, south of Paris, and at Montmartre and other hills in Paris itself, or in its suburbs. At the bottom of these sands a green clay occurs, containing a small oyster, Ostrea cyathula, Lam., which, although of slight thickness, is spread over a wide area. This clay rests immediately on the Paris gypsum, or that series of beds of gypsum and gypseous marl from which Cuvier first obtained several species of Palaeotherium and other extinct mammalia. (Bulletin 1856 Journal volume 12 page 768.)
At this junction of the clay and the gypsum the majority of French geologists have always drawn the line between the Middle and Lower Tertiary, or between the Miocene and Eocene formations, regarding the Fontainebleau sands and the Ostrea cyathula clay as the base of the Miocene, and the gypsum, with its mammalia, as the top of the Eocene group. I formerly dissented from this division, but I now find that I must admit it to be the only one which will agree with the distribution of the Miocene mammalia, while even the mollusca of the Fontainebleau sands, which were formerly supposed to present at preponderance of affinities to an Eocene fauna, have since been shown to agree more closely with the fossils of certain deposits always regarded as Middle Tertiary at Mayence and in Belgium. In fact, we are now arriving at that stage of progress when the line, wherever it be drawn between Miocene and Eocene, will be an arbitrary one, or one of mere convenience, as I shall have an opportunity of showing when the Upper Eocene formations in the Isle of Wight are described in the sixteenth chapter.
LOWER MIOCENE OF CENTRAL FRANCE.
Lacustrine strata, belonging, for the most part, to the same Miocene system as the Calcaire de la Beauce, are again met with farther south in Auvergne, Cantal, and Velay. They appear to be the monuments of ancient lakes, which, like some of those now existing in Switzerland, once occupied the depressions in a mountainous region, and have been each fed by one or more rivers and torrents. The country where they occur is almost entirely composed of granite and different varieties of granitic schist, with here and there a few patches of Secondary strata, much dislocated, and which have suffered great denudation. There are also some vast piles of volcanic matter, the greater part of which is newer than the fresh-water strata, and is sometimes seen to rest upon them, while a small part has evidently been of contemporaneous origin. Of these igneous rocks I shall treat more particularly in the sequel.
The study of these regions possesses a peculiar interest very distinct in kind from that derivable from the investigation either of the Parisian or English Tertiary areas. For we are presented in Auvergne with the evidence of a series of events of astonishing magnitude and grandeur, by which the original form and features of the country have been greatly changed, yet never so far obliterated but that they may still, in part at least, be restored in imagination. Great lakes have disappeared– lofty mountains have been formed, by the reiterated emission of lava, preceded and followed by showers of sand and scoriae– deep valleys have been subsequently furrowed out through masses of lacustrine and volcanic origin– at a still later date, new cones have been thrown up in these valleys– new lakes have been formed by the damming up of rivers– and more than one assemblage of quadrupeds, birds, and plants, Eocene, Miocene, and Pliocene, have followed in succession; yet the region has preserved from first to last its geographical identity; and we can still recall to our thoughts its external condition and physical structure before these wonderful vicissitudes began, or while a part only of the whole had been completed. There was first a period when the spacious lakes, of which we still may trace the boundaries, lay at the foot of mountains of moderate elevation, unbroken by the bold peaks and precipices of Mont Dor, and unadorned by the picturesque outline of the Puy de Dome, or of the volcanic cones and craters now covering the granitic platform. During this earlier scene of repose deltas were slowly formed; beds of marl and sand, several hundred feet thick, deposited; siliceous and calcareous rocks precipitated from the waters of mineral springs; shells and insects imbedded, together with the remains of the crocodile and tortoise, the eggs and bones of water-birds, and the skeletons of quadrupeds, most of them of genera and species characteristic of the Miocene period. To this tranquil condition of the surface succeeded the era of volcanic eruptions, when the lakes were drained, and when the fertility of the mountainous district was probably enhanced by the igneous matter ejected from below, and poured down upon the more sterile granite. During these eruptions, which appear to have taken place towards the close of the Miocene epoch, and which continued during the Pliocene, various assemblages of quadrupeds successively inhabited the district, among which are found the genera mastodon, rhinoceros, elephant, tapir, hippopotamus, together with the ox, various kinds of deer, the bear, hyaena, and many beasts of prey which ranged the forest or pastured on the plain, and were occasionally overtaken by a fall of burning cinders, or buried in flows of mud, such as accompany volcanic eruptions. Lastly, these quadrupeds became extinct, and gave place in their turn to the species now existing. There are no signs, during the whole time required for this series of events, of the sea having intervened, nor of any denudation which may not have been accomplished by currents in the different lakes, or by rivers and floods accompanying repeated earthquakes, or subterranean movements, during which the levels of the district have in some places been materially modified, and perhaps the whole upraised relatively to the surrounding parts of France.
AUVERGNE.
The most northern of the fresh-water groups is situated in the valley-plain of the Allier, which lies within the department of the Puy de Dome, being the tract which went formerly by the name of the Limagne d’Auvergne. The average breadth of this tract is about twenty miles; and it is for the most part composed of nearly horizontal strata of sand, sandstone, calcareous marl, clay, and limestone, none of which observe a fixed and invariable order of superposition. The ancient borders of the lake wherein the fresh-water strata were accumulated may generally be traced with precision, the granite and other ancient rocks rising up boldly from the level country. The actual junction, however, of the lacustrine beds and the granite is rarely seen, as a small valley usually intervenes between them. The fresh-water strata may sometimes be seen to retain their horizontality within a very slight distance of the border-rocks, while in some places they are inclined, and in few instances vertical. The principal divisions into which the lacustrine series may be separated are the following:– first, Sandstone, grit, and conglomerate, including red marl and red sandstone; secondly, Green and white foliated marls; thirdly, Limestone, or travertin, often oolitic in structure; fourthly, Gypseous marls.
The relations of these different groups can not be learnt by the study of any one section; and the geologist who sets out with the expectation of finding a fixed order of succession may perhaps complain that the different parts of the basin give contradictory results. The arenaceous division, the marls, and the limestone may all be seen in some places to alternate with each other; yet it can by no means be affirmed that there is no order of arrangement. The sands, sandstone, and conglomerate constitute in general a littoral group; the foliated white and green marl, a contemporaneous central deposit more than 700 feet thick, and thinly foliated, a character which often arises from the innumerable thin shells or carapace valves shed by the small crustacean called Cypris in the ancient lakes of Auvergne; and lastly the limestone is for the most part subordinate to the newer portions of both the above formations.
It seems that, when the ancient lake of the Limagne first began to be filled with sediment, no volcanic action had yet produced lava and scoriae on any part of the surface of Auvergne. No pebbles, therefore, of lava were transported into the lake– no fragments of volcanic rocks imbedded in the conglomerate. But at a later period, when a considerable thickness of sandstone and marl had accumulated, eruptions broke out, and lava and tuff were deposited, at some spots, alternately with the lacustrine strata. It is not improbable that cold and thermal springs, holding different mineral ingredients in solution, became more numerous during the successive convulsions attending this development of volcanic agency, and thus deposits of carbonate and sulphate of lime, silex, and other minerals were produced. Hence these minerals predominate in the uppermost strata. The subterranean movements may then have continued until they altered the relative levels of the country, and caused the waters of the lakes to be drained off, and the further accumulation of regular fresh-water strata to cease.
LOWER MIOCENE MAMMALIA OF THE LIMAGNE.
It is scarcely possible to determine the age of the oldest part of the fresh- water series of the Limagne, large masses both of the sandy and marly strata being devoid of fossils. Some of the lowest beds may be of Upper Eocene date, although, according to M. Pomel, only one bone of a Palaeotherium has been discovered in Auvergne. But in Velay, in strata containing some species of fossil mammalia common to the Limagne, no less than four species of Palaeothere have been found by M. Aymard, and one of these is generally supposed to be identical with Palaeotherium magnum, an undoubted Upper Eocene fossil, of the Paris gypsum, the other three being peculiar.
Not a few of the other mammalia of the Limagne belong undoubtedly to genera and species elsewhere proper to the Lower Miocene. Thus, for example, the Cainotherium of Bravard, a genus not far removed from the Anoplotherium, is represented by several species, one of which, as I learn from Mr. Waterhouse, agrees with Microtherium Renggeri of the Mayence basin. In like manner, the Amphitragulus elegans of Pomel, an Auvergne fossil, is identified by Waterhouse with Dorcatherium nanum of Kaup, a Rhenish species from Weissenau, near Mayence. A small species, also, of rodent, of the genus Titanomys of H. von Meyer, is common to the Lower Miocene of Mayence and the Limagne d’Auvergne, and there are many other points of agreement which the discordance of nomenclature tends to conceal. A remarkable carnivorous genus, the Hyaenodon of Laizer, is represented by more than one species. The same genus has also been found in the Upper Eocene marls of Hordwell Cliff, Hampshire, just below the level of the Bembridge Limestone, and therefore a formation older than the Gypsum of Paris. Several species of opossum (Didelphis) are met with in the same strata of the Limagne. The total number of mammalia enumerated by M. Pomel as appertaining to the Lower Miocene fauna of the Limagne and Velay falls little short of a hundred, and with them are associated some large crocodiles and tortoises, and some Ophidian and Batrachian reptiles.
LOWER MOLASSE OF SWITZERLAND.
The two upper divisions of the Swiss Molasse– the one fresh-water, the other marine– have already been described in the preceding chapter. I shall now proceed to treat of the third division, which is of Lower Miocene age. Nearly the whole of this Lower Molasse is fresh-water, yet some of the inferior beds contain a mixture of marine and fluviatile shells, the Cerithium margaritaceum, a well-known Lower Miocene fossil, being one of the marine species. Notwithstanding, therefore, that some of these Lower Miocene strata consist of old shingle-beds several thousand feet in thickness, as in the Rigi, near Lucerne, and in the Speer, near Wesen, mountains 5000 and 7000 feet above the sea, the deposition of the whole series must have begun at or below the sea- level.
The conglomerates, as might be expected, are often very unequal in thickness, in closely adjoining districts, since in a littoral formation accumulations of pebbles would swell out in certain places where rivers entered the sea, and would thin out to comparatively small dimensions where no streams or only small ones came down to the coast. For ages, in spite of a gradual depression of the land and adjacent sea-bottom, the rivers continued to cover the sinking area with their deltas; until finally, the subsidence being in excess, the sea of the Middle Molasse gained upon the land, and marine beds were thrown down over the dense mass of fresh-water and brackish-water deposit, called the Lower Molasse, which had previously accumulated.
FLORA OF THE LOWER MOLASSE.
In part of the Swiss Molasse, which belongs exclusively to the Lower Miocene period, the number of plants has been estimated at more than 500 species, somewhat exceeding those which were before enumerated as occurring in the two upper divisions. The Swiss Lower Miocene may best be studied on the northern borders of the Lake of Geneva, between Lausanne and Vevay, where the contiguous villages of Monod and Rivaz are situated. The strata there, which I have myself examined, consist of alternations of conglomerate, sandstone, and finely laminated marls with fossil plants. A small stream falls in a succession of cascades over the harder beds of pudding-stone, which resist, while the sandstone and plant-bearing shales and marls give way. From the latter no less than 193 species of plants have been obtained by the exertions of MM. Heer and Gaudin, and they are considered to afford a true type of the vegetation of the Lower Miocene formations of Switzerland– a vegetation departing farther in its character from that now flourishing in Europe than any of the higher members of the series before alluded to, and yet displaying so much affinity to the flora of Oeningen as to make it natural for the botanist to refer the whole to one and the same Miocene period. There are, indeed, no less than 81 species of these Older Miocene plants which pass up into the flora of Oeningen.
This fact is important as bearing on the propriety of classing the Lower Molasse of Switzerland as belonging to the Miocene rather than to the latter part of the Eocene period. There are, indeed, so many types among the fossils, both specific and generic, which have a wide range through the whole of the Molasse, that a unity of character is thereby stamped on the whole flora, in spite of the contrast between the plants of the uppermost and lowest formations, or between Oeningen and Monod. The proofs of a warmer climate, and the excess of arborescent over herbaceous plants, and of evergreen trees over deciduous species, are characters common to the whole flora, but which are intensified as we descend to the inferior deposits.
(FIGURE 151. Sabal major, Unger sp. Vevay. Lower Miocene; Heer, Plate 41.)
Nearly all the plants at Monod are contained in three layers of marl separated by two of soft sandstone. The thickness of the marls is ten feet, and vegetable matter predominates so much in some layers as to form an imperfect lignite. One bed is filled with large leaves of a species of fig (Ficus populina), and of a hornbeam (Carpinus grandis), the strength of the wind having probably been great when they were blown into the lake; whereas another contiguous layer contains almost exclusively smaller leaves, indicating, apparently, a diminished strength in the wind. Some of the upper beds at Monod abound in leaves of Proteaceae, Cyperaceae, and ferns, while in some of the lower ones Sequoia, Cinnamomum, and Sparganium are common. In one bed of sandstone the trunk of a large palm-tree was found unaccompanied by other fossils, and near Vevay, in the same series of Lower Miocene strata, the leaves of a palm of the genus Sabal (Figure 151), a genus now proper to America, were obtained.
Among other genera of the same class is a Flabellaria occurring near Lausanne, and a magnificent Phoenicites allied to the date palm. When these plants flourished the climate must have been much hotter than now. The Alps were no doubt much lower, and the palms now found fossil in strata elevated 2000 feet above the sea grew nearly at the sea-level, as is demonstrated by the brackish- water character of some of the beds into which they were carried by winds or rivers from the adjoining coast.
(FIGURE 152. Banksia.
a. Fruit of fossil Banksia.
b. Leaf of Banksia Deekiana.)
In the same plant-bearing deposits of the Lower Molasse in Switzerland leaves have been found which have been ascribed to the order Proteaceae already spoken of as well represented in the Oeningen beds (see Chapter 14). The Proteas and other plants of this family now flourish at the Cape of Good Hope; while the Banksias, and a set of genera distinct from those of Africa, grow most luxuriantly in the southern and temperate parts of Australia. They were probably inhabitants, says Heer, of dry hilly ground, and the stiff leathery character of their leaves must have been favourable to their preservation, allowing them to float on a river for great distances without being injured, and then to sink, when water-logged, to the bottom. It has been objected that the fruit of the Proteaceae is of so tough and enduring a texture that it ought to have been more commonly met with; but in the first place we must not forget the numerous cones found in the Eocene strata of Sheppey, which all admit to be proteaceous and to belong to at least two species (see Chapter 14). Secondly, besides the fruit of Hakea before mentioned (Chapter 14), Heer found associated with fossil leaves, having the exact form and nervation of Banksia, fruit precisely such as may have come from a cone of that plant, and lately he has received another similar fruit from the Lower Miocene strata of Lucerne. They may have fallen out of a decayed cone in the same way as often happens to the seeds of the spruce fir, Pinus abies, found scattered over the ground in our woods. It is a known fact that among the living Proteaceae the cones are very firmly attached to the branches, so that the seeds drop out without the cone itself falling to the ground, and this may perhaps be the reason why, in some instances in which fossil seeds have been found, no traces of the cone have been observed.
(FIGURE 153. Sequoia Langsdorfii. Ad. Brong., 1/3 natural size. Rivaz, near Lausanne; Heer, Plate 21 Figure 4. Upper and Lower Miocene and Lower Pliocene, Val d’Arno.
a. Branch with leaves.
b. Young cone.)
Among the Coniferae the Sequoia here figured is common at Rivaz, and is one of the most universal plants in the Lowest Miocene of Switzerland, while it also characterises the Miocene Brown Coals of Germany and certain beds of the Val d’Arno, which I have called Older Pliocene, Chapter 13.
(FIGURE 154. Lastraea stiriaca, Unger; Heer’s Flora, Plate 143 Figure 8. Natural size. Lower and Upper Miocene, Switzerland. a. Specimen from Monod, showing the position of the sori on the middle of the tertiary nerves.
b. More common appearance, where the sori remain and the nerves are obliterated.)
Among the ferns met with in profusion at Monod is the Lastraea stiriaca, Unger, which has a wide range in the Miocene period from strata of the age of Oeningen to the lowest part of the Swiss Molasse. In some specimens, as shown in Figure 154, the fructification is distinctly seen.
(FIGURE 155. Cinnamomum Rossmassleri, Heer. Daphnogene cinnamomifolia, Unger. Upper and Lower Miocene, Switzerland and Germany.)
Among the laurels several species of Cinnamomum are very conspicuous. Besides the C. polymorphum, before figured, Chapter 14, another species also ranges from the Lower to the Upper Molasse of Switzerland, and is very characteristic of different deposits of Brown Coal in Germany. It has been called Cinnamomum Rossmassleri by Heer (see Figure 155). The leaves are easily recognised as having two side veins, which run up uninterruptedly to their point.
AMERICAN CHARACTER OF THE FLORA.
If we consider not merely the number of species but those plants which constitute the mass of the Lower Miocene vegetation, we find the European part of the fossil flora very much less prominent than in the Oeningen beds, while the foreground is occupied by American forms, by evergreen oaks, maples, poplars, planes, Liquidambar, Robinia, Sequoia, Taxodium, and ternate-leaved pines. There is also a much greater fusion of the characters now belonging to distinct botanical provinces than in the Upper Miocene flora, and we shall find this fusion still more strikingly exemplified as we go back to the antecedent Eocene and Cretaceous periods.
Professor Heer has advocated the doctrine, first advanced by Unger to explain the large number of American genera in the Miocene flora of Europe, that the present basin of the Atlantic was occupied by land over which the Miocene flora could pass freely. But other able botanists have shown that it is far more probable that the American plants came from the east and not from the west, and instead of reaching Europe by the shortest route over an imaginary Atlantis, migrated in an opposite direction, crossing the whole of Asia.
ARCTIC MIOCENE FLORA.
But when we indulge in speculations as to the geographical origin of the Miocene plants of Central Europe, we must take into account the discoveries recently made of a rich terrestrial flora having flourished in the Arctic Regions in the Miocene period from which many species may have migrated from a common centre so as to reach the present continents of Europe, Asia, and America. Professor Heer has examined the various collections of fossil plants that have been obtained in North Greenland (latitude 70 degrees), Iceland, Spitzbergen, and other parts of the Arctic regions, and has determined that they are of Miocene age and indicate a temperate climate. (Heer “Miocene baltische Flora” and “Fossil-flora von Alaska” 1869.) Including the collections recently brought from Greenland by Mr. Whymper, the Arctic Miocene flora now comprises 194 species, and that of Greenland 137 species, of which 46, or exactly one-third, are identical with plants found in the Miocene beds of Central Europe. Considerably more than half the number are trees, which is the more remarkable since, at the present day, trees do not exist in any part of Greenland even 10 degrees farther south.
More than thirty species of Coniferae have been found, including several Sequoias (allied to the gigantic Wellingtonia of California), with species of Thujopsis and Salisburia now peculiar to Japan. There are also beeches, oaks, planes, poplars, maples, walnuts, limes, and even a magnolia, two cones of which have recently been obtained, proving that this splendid evergreen not only lived but ripened its fruit within the Arctic circle. Many of the limes, planes, and oaks were large-leaved species, and both flowers and fruit, besides immense quantities of leaves, are in many cases preserved. Among the shrubs were many evergreens, as Andromeda, and two extinct genera, Daphnogene and M’Clintockia, with fine leathery leaves, together with hazel, blackthorn, holly, logwood, and hawthorn. A species of Zamia (Zamites) grew in the swamps, with Potamogeton, Sparganium, and Menyanthes, while ivy and vines twined around the forest trees and broad-leaved ferns grew beneath their shade. Even in Spitzbergen, as far north as latitude 78 degrees 56′, no less than ninety-five species of fossil plants have been obtained, including Taxodium of two species, hazel, poplar, alder, beech, plane-tree, and lime. Such a vigorous growth of trees within 12 degrees of the pole, where now a dwarf willow and a few herbaceous plants form the only vegetation, and where the ground is covered with almost perpetual snow and ice, is truly remarkable.
The identity of so many of the fossils with Miocene species of Central Europe and Italy not only proves that the climate of Greenland was much warmer than it is now, but also renders it probable that a much more uniform climate prevailed over the entire northern hemisphere. This is also indicated by the whole character of the Upper Miocene flora of Central Europe, which does not necessitate a mean temperature very much greater than exists at present, if we suppose such absence of winter cold as is proper to insular climates. Professor Heer believes that the mean temperature of North Greenland must have been at least 30 degrees higher than at present, while an addition of 10 degrees to the mean temperature of Central Europe would probably be as much as was required. The chief locality where this wonderful flora is preserved is at Atanekerdluk in North Greenland (latitude 70 degrees), on a hill at an elevation of about 1200 feet above the sea. There is here a considerable succession of sedimentary strata pierced by volcanic rocks. Fossil plants occur in all the beds, and the erect trunks as thick as a man’s body which are sometimes found, together with the abundance of specimens of flowers and fruit in good preservation, sufficiently prove that the plants grew where they are now found. At Disco island and other localities on the same part of the coast, good coal is abundant, interstratified with beds of sandstone, in some of which fossil plants have also been found, similar to those at Atanekerdluk.
LOWER MIOCENE, BELGIUM.
(FIGURE 156. Leda (Nucula) Deshayesiana, Nyst.)
(FIGURE 157. Vanessa pluto; natural size. Lower Miocene, Radaboj, Croatia.)
The Upper Miocene Bolderberg beds, mentioned in Chapter 14, rest on a Lower Miocene formation called the Rupelian of Dumont. This formation is best seen at the villages of Rupelmonde and Boom, ten miles south of Antwerp, on the banks of the Scheldt and near the junction with it of a small stream called the Rupel. A stiff clay abounding in fossils is extensively worked at the above localities for making tiles. It attains a thickness of about 100 feet, and though very different in age, much resembles in mineral character the “London clay,” containing, like it, septaria or concretions of argillaceous limestone traversed by cracks in the interior, which are filled with calc-spar. The shells, referable to about forty species, have been described by MM. Nyst and De Koninck. Among them Leda (or Nucula) Deshayesiana (see Figure 156) is by far the most abundant; a fossil unknown as yet in the English tertiary strata, but when young much resembling Leda amygdaloides of the London Clay proper (see Figure 213 Chapter 16). Among other characteristic shells are Pecten Hoeninghausii, and a species of Cassidaria, and several of the genus Pleurotoma. Not a few of these testacea agree with English Eocene species, such as Actaeon simulatus, Sowb, Cancellaria evulsa, Brander, Corbula pisum (Figure 157), and Nautilus (Aturia) ziczac. They are accompanied by many teeth of sharks, as Lamna contortidens, Ag., Oxyrhinaxiphodon, Ag., Carcharodon angustidens (see Figure 196 Chapter 16), Ag., and other fish, some of them common to the Middle Eocene strata.
KLEYN SPAWEN BEDS.
The succession of the Lower Miocene strata of Belgium can be best studied in the environs of Kleyn Spawen, a village situated about seven miles west of Maestricht, in the old province of Limburg in Belgium. In that region, about 200 species of testacea, marine and fresh-water, have been obtained, with many foraminifera and remains of fish. In none of the Belgian Lower Miocene strata could I find any nummulites; and M. d’Archiac had previously observed that these foraminifera characterise his “Lower Tertiary Series,” as contrasted with the Middle, and they therefore serve as a good test of age between Eocene and Miocene, at least in Belgium and the North of France. (D’Archiac Monograph pages 79, 100.) Between the Bolderberg beds and the Rupelian clay there is a great gap in Belgium, which seems, according to M. Beyrich, to be filled up in the North of Germany by what he calls the Sternberg beds, and which, had Dumont found them in Belgium, he might probably have termed Upper Rupelian.
LOWER MIOCENE OF GERMANY.
RUPELIAN CLAY OF HERMSDORF, NEAR BERLIN.
Professor Beyrich has described a mass of clay, used for making tiles, within seven miles of the gates of Berlin, near the village of Hermsdorf, rising up from beneath the sands with which that country is chiefly overspread. This clay is more than forty feet thick, of a dark bluish-grey colour, and, like that of Rupelmonde, contains septaria. Among other shells, the Leda Deshayesiana, before mentioned (Figure 156), abounds, together with many species of Pleurotoma, Voluta, etc., a certain proportion of the fossils being identical in species with those of Rupelmonde.
MAYENCE BASIN.
An elaborate description has been published by Dr. F. Sandberger of the Mayence tertiary area, which occupies a tract from five to twelve miles in breadth, extending for a great distance along the left bank of the Rhine from Mayence to the neighbourhood of Manheim, and which is also found to the east, north, and south-west of Frankfort. M. De Koninck, of Liege, first pointed out to me that the purely marine portion of the deposit contained many species of shells common to the Kleyn Spawen beds, and to the clay of Rupelmonde, near Antwerp. Among these he mentioned Cassidaria depressa, Tritonium argutum, Brander (T. flandricum, De Koninck), Tornatella simulata, Aporrhais Sowbyi, Leda Deshayesiana (Figure 156), Corbula pisum, (Figure 158) and others.
LOWER MIOCENE BEDS OF CROATIA.
The Brown Coal of Radaboj, near Angram in Croatia, not far from the borders of Styria, is covered, says Von Buch, by beds containing the marine shells of the Vienna basin, or, in other words, by Upper Miocene or Falunian strata. They appear to correspond in age to the Mayence basin, or to the Rupelian strata of Belgium. They have yielded more than 200 species of fossil plants, described by the late Professor Unger. These plants are well preserved in a hard marlstone, and contain several palms; among them the Sabal, Figure 151, and another genus allied to the date-palm Phoenicites spectabilis. The only abundant plant among the Radaboj fossils which is characteristic of the Upper Miocene period is the Populus mutabilis, whereas no less than fifty of the Radaboj species are common to the more ancient flora of the Lower Molasse of Switzerland.
The insect fauna is very rich, and, like the plants, indicates a more tropical climate than do the fossils of Oeningen presently to be mentioned. There are ten species of Termites, or white ants, some of gigantic size, and large dragon- flies with speckled wings, like those of the Southern States in North America; there are also grasshoppers of considerable size, and even the Lepidoptera are not unrepresented. In one instance, the pattern of a butterfly’s wing has escaped obliteration in the marl-stone of Radaboj; and when we reflect on the remoteness of the time from which it has been faithfully transmitted to us, this fact may inspire the reader with some confidence as to the reliable nature of the characters which other insects of a more durable texture, such as the beetles, may afford for specific determination. The Vanessa above figured retains, says Heer, some of its colours, and corresponds with Vanessa Hadena of India.
Professor Beyrich has made known to us the existence of a long succession of marine strata in North Germany, which lead by an almost gradual transition from beds of Upper Miocene age to others of the age of the base of the Lower Miocene. Although some of the German lignites called Brown Coal belong to the upper parts of this series, the most important of them are of Lower Miocene date, as, for example, those of the Siebengebirge, near Bonn, which are associated with volcanic rocks.
Professor Beyrich confines the term “Miocene” to those strata which agree in age with the faluns of Touraine, and he has proposed the term “Oligocene” for those older formations called Lower Miocene in this work.
LOWER MIOCENE OF ITALY.
In the hills of which the Superga forms a part there is a great series of Tertiary strata which pass downward into the Lower Miocene. Even in the Superga itself there are some fossil plants which, according to Heer, have never been found in Switzerland so high as the marine Molasse, such as Banksia longifolia, and Carpinus grandis. In several parts of the Ligurian Apennines, as at Dego and Carcare, the Lower Miocene appears, containing some nummulites, and at Cadibona, north of Savona, fresh-water strata of the same age occur, with dense beds of lignite inclosing remains of the Anthracotherium magnum and Anthracotherium minimum, besides other mammalia enumerated by Gastaldi. In these beds a great number of the Lower Miocene plants of Switzerland have been discovered.
LOWER MIOCENE OF ENGLAND– HEMPSTEAD BEDS.
We have already stated that the Upper Miocene formation is nowhere represented in the British Isles; but strata referable to the Lower Miocene period are found both in England, Scotland, and Ireland. In the Hampshire basin these occupy a very small superficial area, having been discovered by the late Edward Forbes at Hempstead near Yarmouth, in the northern part of the Isle of Wight, where they are 170 feet thick, and rich in characteristic marine shells. They overlie the uppermost of an extensive series of Eocene deposits of marine, brackish, and fresh-water formations, which rest on the Chalk and terminate upward in strata corresponding in age to the Paris gypsum, and containing the same extinct genera of quadrupeds, Palaeotherium, Anoplotherium, and others which Cuvier first described. The following is the succession of these Lower Miocene strata, most of them exposed in a cliff east of Yarmouth:
(FIGURE 158. Corbula pisum. Hempstead Beds, Isle of Wight.)
(FIGURE 159. Cyrena semistriata. Hempstead Beds.)
1. The uppermost or Corbula beds, consisting of marine sands and clays, contain Voluta Rathieri, a characteristic Lower Miocene shell; Corbula pisum (Figure 158), a species common to the Upper Eocene clay of Barton; Cyrena semistriata (Figure 159), several Cerithia, and other shells peculiar to this series.
(FIGURE 160. Cerithium plicatum, Lam., Hempstead.)
(FIGURE 161. Cerithium elegans. Hempstead.)
(FIGURE 162. Rissoa Chastelii, Nyst, sp. Hempstead, Isle of Wight.)
(FIGURE 163. Paludina lenta. Hempstead Bed.)
2. Next below are fresh-water and estuary marls and carbonaceous clays in the brackish-water portion of which are found abundantly Cerithium plicatum, Lam. (Figure 160), Cerithium elegans (Figure 161), and Cerithium tricinctum; also Rissoa Chastelii (Figure 162), a very common Kleyn Spawen shell, and which occurs in each of the four subdivisions of the Hempstead series down to its base, where it passes into the Bembridge beds. In the fresh-water portion of the same beds Paludina lenta (Figure 163) occurs; a shell identified by some conchologists with a species now living, Paludina unicolor; also several species of Lymneus, Planorbis, and Unio.
3. The next series, or middle fresh-water and estuary marls, are distinguished by the presence of Melania fasciata, Paludina lenta, and clays with Cypris; the lowest bed contains Cyrena semistriata (Figure 159), mingled with Cerithia and a panopaea.
4. The lower fresh-water and estuary marls contain Melania costata, Sowerby, Melanopsis, etc. The bottom bed is carbonaceous, and called the “Black band,” in which Rissoa Chastelii (Figure 162), before alluded to, is common. This bed contains a mixture of Hempstead shells with those of the underlying Upper Eocene or Bembridge series. The mammalia, among which is Hyopotamus bovinus, differ, so far as they are known, from those of the Bembridge beds. Among the plants, Professor Heer has recognised four species common to the lignite of Bovey Tracey, a Lower Miocene formation presently to be described: namely, Sequoia Couttsiae, Heer; Andromeda reticulata, Ettings.; Nelumbium (Nymphoea) doris, Heer; and Carpolithes Websteri, Brong. (Pengelly, preface to The Lignite Formation of Bovey Tracey page 17. London 1863.) The seed-vessels of Chara medicaginula, Brong, and Chara helicteres are characteristic of the Hempstead beds generally.
The Hyopotamus belongs to the hog tribe, or the same family as the Anthracotherium, of which seven species, varying in size from the hippopotamus to the wild boar, have been found in Italy and other part of Europe associated with the lignites of the Lower Miocene period.
LIGNITES AND CLAYS OF BOVEY TRACEY, DEVONSHIRE.
Surrounded by the granite and other rocks of the Dartmoor hills in Devonshire, is a formation of clay, sand, and lignite, long known to geologists as the Bovey Coal formation, respecting the age of which, until the year 1861, opinions were very unsettled. This deposit is situated at Bovey Tracey, a village distant eleven miles from Exeter in a south-west, and about as far from Torquay in a north-west direction. The strata extend over a plain nine miles long, and they consist of the materials of decomposed and worn-down granite and vegetable matter, and have evidently filled up an ancient hollow or lake-like expansion of the valleys of the Bovey and Teign.
The lignite is of bad quality for economical purposes, as there is a great admixture in it of iron pyrites, and it emits a sulphurous odour, but it has been successfully applied to the baking of pottery, for which some of the fine clays are well adapted. Mr. Pengelly has confirmed Sir H. De la Beche’s opinion that much of the upper portion of this old lacustrine formation has been removed by denudation. (Philosophical Transactions 1863. Paper by W. Pengelly F.R.S. and Dr. Oswald Heer.)
At the surface is a dense covering of clay and gravel with angular stones probably of the Post-pliocene period, for in the clay are three species of willow and the dwarf birch, Betula nana, indicating a climate colder than that of Devonshire at the present day.
Below this are Lower Miocene strata about 300 feet in thickness, in the upper part of which are twenty-six beds of lignite, clay, and sand, and at their base a ferruginous quartzose sand, varying in thickness from two to twenty-seven feet. Below this sand are forty-five beds of alternating lignite and clay. No shells or bones of mammalia, and no insect, with the exception of one fragment of a beetle (Buprestis); in a word, no organic remains, except plants, have as yet been found. These plants occur in fourteen of the beds– namely, in two of the clays, and the rest in the lignites. One of the beds is a perfect mat of the debris of a coniferous tree, called by Heer Sequoia Couttsiae, intermixed with leaves of ferns. The same Sequoia (before mentioned as a Hempstead fossil) is spread through all parts of the formation, its cones, and seeds, and branches of every age being preserved. It is a species supplying a link between Sequoia Langsdorfii (see Figure 153) and Sequoia Sternbergi, the widely spread fossil representatives of the two living trees Sequoia sempervirens and Sequoia gigantea (or Wellingtonia), both now confined to California. Another bed is full of the large rhizomes of ferns, while two others are rich in dicotyledonous leaves. In all, Professor Heer enumerates forty-nine species of plants, twenty of which are common to the Miocene beds of the Continent, a majority of them being characteristic of the Lower Miocene. The new species, also of Bovey, are allied to plants of the older Miocene deposits of Switzerland, Germany, and other Continental countries. The grape-stones of two species of vine occur in the clays, and leaves of the fig and seeds of a water-lily. The oak and laurel have supplied many leaves. Of the triple-nerved laurels several are referred to Cinnamomum. There are leaves also of a palm of which the genus is not determined. Leaves also of proteaceous forms, like some of the Continental fossils before mentioned, occur, and ferns like the well-known Lastraea stiriaca (Figure 154), displaying at Bovey, as in Switzerland, its fructification.
The croziers of some of the young ferns are very perfect, and were at first mistaken by collectors for shells of the genus Planorbis. On the whole, the vegetation of Bovey implies the existence of a sub-tropical climate in Devonshire, in the Lower Miocene period.
SCOTLAND: ISLE OF MULL.
In the sea-cliffs forming the headland of Ardtun, on the west coast of Mull, in the Hebrides, several bands of tertiary strata containing leaves of dicotyledonous plants were discovered in 1851 by the Duke of Argyll. (Quarterly Geological Journal 1851 page 19.) From his description it appears that there are three leaf-beds, varying in thickness from 1 1/2 to 5 1/2 feet, which are interstratified with volcanic tuff and trap, the whole mass being about 130 feet in thickness. A sheet of basalt 40 feet thick covers the whole; and another columnar bed of the same rock, ten feet thick, is exposed at the bottom of the cliff. One of the leaf-beds consists of a compressed mass of leaves unaccompanied by any stems, as if they had been blown into a marsh where a species of Equisetum grew, of which the remains are plentifully imbedded in clay.
It is supposed by the Duke of Argyll that this formation was accumulated in a shallow lake or marsh in the neighbourhood of a volcano, which emitted showers of ashes and streams of lava. The tufaceous envelope of the fossils may have fallen into the lake from the air as volcanic dust, or have been washed down into it as mud from the adjoining land. Even without the aid of organic remains we might have decided that the deposit was newer than the chalk, for chalk- flints containing cretaceous fossils were detected by the duke in the principal mass of volcanic ashes or tuff. (Quarterly Geological Journal 1851 page 90.)
The late Edward Forbes observed that some of the plants of this formation resembled those of Croatia, described by Unger, and his opinion has been confirmed by Professor Heer, who found that the conifer most prevalent was the Sequoia Langsdorfii (Figure 153), also Corylus grossedentata, a Lower Miocene species of Switzerland and of Menat in Auvergne. There is likewise a plane-tree, the leaves of which seem to agree with those of Platanus aceroides (Figure 141 Chapter 14), and a fern which is as yet peculiar to Mull, Filicites hebridica, Forbes.
These interesting discoveries in Mull led geologists to suspect that the basalt of Antrim, in Ireland, and of the celebrated Giant’s Causeway, might be of the same age. The volcanic rocks that overlie the chalk, and some of the strata associated with and interstratified between masses of basalt, contain leaves of dicotyledonous plants, somewhat imperfect, but resembling the beech, oak, and plane, and also some coniferae of the genera pine and Sequoia. The general dearth of strata in the British Isles, intermediate in age between the formation of the Eocene and Pliocene periods, may arise, says Professor Forbes, from the extent of dry land which prevailed in that vast interval of time. If land predominated, the only monuments we are likely ever to find of Miocene date are those of lacustrine and volcanic origin, such as the Bovey Coal in Devonshire, the Ardtun beds in Mull, or the lignites and associated basalts in Antrim.
LOWER MIOCENE, UNITED STATES: NEBRASKA.
In the territory of Nebraska, on the Upper Missouri, near the Platte River, latitude 42 degrees N., a tertiary formation occurs, consisting of white limestone, marls, and siliceous clay, described by Dr. D. Dale Owen (David Dale Owen Geological Survey of Wisconsin etc. Philadelphia 1852.), in which many bones of extinct quadrupeds, and of chelonians of land or fresh-water forms, are met with. Among these, Dr. Leidy describes a gigantic quadruped, called by him Titanotherium, nearly allied to the Palaeotherium, but larger than any of the species found in the Paris gypsum. With these are several species of the genus Oreodon, Leidy, uniting the characters of pachyderms and ruminants also; Eucrotaphus, another new genus of the same mixed character; two species of rhinoceros of the sub-genus Acerotherium, a Lower Miocene form of Europe before mentioned; two species of Archaeotherium, a pachyderm allied to Chaeropotamus and Hyracotherium; also Paebrotherium, an extinct ruminant allied to Dorcatherium, Kaup; also Agriochoerus, of Leidy, a ruminant allied to Merycopotamus of Falconer and Cautley; and, lastly, a large carnivorous animal of the genus Machairodus, the most ancient example of which in Europe occurs in the Lower Miocene strata of Auvergne, but of which some species are found in Pliocene deposits. The turtles are referred to the genus Testudo, but have some affinity to Emys. On the whole, the Nebraska formation is probably newer than the Paris gypsum, and referable to the Lower Miocene period, as above defined.
CHAPTER XVI.
EOCENE FORMATIONS.
Eocene Areas of North of Europe.
Table of English and French Eocene Strata. Upper Eocene of England.
Bembridge Beds.
Osborne or St. Helen’s Beds.
Headon Series.
Fossils of the Barton Sands and Clays. Middle Eocene of England.
Shells, Nummulites, Fish and Reptiles of the Bracklesham Beds and Bagshot Sands. Plants of Alum Bay and Bournemouth.
Lower Eocene of England.
London Clay Fossils.
Woolwich and Reading Beds formerly called “Plastic Clay.” Fluviatile Beds underlying Deep-sea Strata. Thanet Sands.
Upper Eocene Strata of France.
Gypseous Series of Montmartre and Extinct Quadrupeds. Fossil Footprints in Paris Gypsum.
Imperfection of the Record.
Calcaire Silicieux.
Gres de Beauchamp.
Calcaire Grossier.
Miliolite Limestone.
Soissonnais Sands.
Lower Eocene of France.
Nummulitic Formations of Europe, Africa, and Asia. Eocene Strata in the United States.
Gigantic Cetacean.
EOCENE AREAS OF THE NORTH OF EUROPE.
(FIGURE 164. Map of the principal Eocene areas of North-western Europe, showing: Shaded dotted: Hypogene rocks and strata older than the Devonian. Shaded horizontal lines: Eocene formations. NB.– the space left blank is occupied by fossiliferous formations from the Devonian to the chalk inclusive.)
The strata next in order in the descending series are those which I term Eocene.
In the map in Figure 164, the position of several Eocene areas in the north of Europe is pointed out. When this map was constructed I classed as the newer part of the Eocene those Tertiary strata which have been described in the last chapter as Lower Miocene, and to which M. Beyrich has given the name of Oligocene. None of these occur in the London Basin, and they occupy in that of Hampshire, as we have seen in Chapter 15, too insignificant a superficial area to be noticed in a map on this scale. They fill a larger space in the Paris Basin between the Seine and the Loire, and constitute also part of the northern limits of the area of the Netherlands which are shaded in the map.
TABLE 16.1. TABLE OF ENGLISH AND FRENCH EOCENE STRATA.
COLUMN 1: NAME OF STRATA.
COLUMN 2: ENGLISH SUBDIVISIONS.
COLUMN 3: FRENCH EQUIVALENTS.
UPPER EOCENE.
A.1: Bembridge series, Isle of Wight: Gypseous series of Montmartre.
A.2: Osborne or St. Helen’s series, Isle of Wight: Calcaire siliceux, or Travertin Inferieur.
A.3: Headon series, Isle of Wight: Calcaire siliceux, or Travertin Inferieur.
A.4: Barton series. Sands and clays of Barton Cliff, Hants: Gres de Beauchamp, or Sables Moyens.
MIDDLE EOCENE.
B.1: Bracklesham series: Calcaire Grossier.
B.2: Alum Bay and Bournemouth beds: Wanting in France?
B.2: Wanting in England?: Soissonnais Sands, or Lits Coquilliers.
LOWER EOCENE.
C.1: London Clay: Argile de Londres, Cassel, near Dunkirk.
C.2: Woolwich and Reading series: Argile plastique and lignite.
C.3: Thanet sands: Sables de Bracheux.
It is in the northern part of the Isle of Wight that we have the uppermost beds of the true Eocene best exhibited– namely, those which correspond in their fossils with the celebrated gypsum of the Paris basin before alluded to in Chapter 15 (see Table 16.1). That gypsum has been selected by almost all Continental geologists as affording the best line of demarkation between the Middle and Lower Tertiary, or, in other words, between the Lower Miocene and Eocene formations.
In reference to Table 16.1 I may observe, that the correlation of the French and English subdivisions here laid down is often a matter of great doubt and difficulty, notwithstanding their geographical proximity. This arises from various circumstances, partly from the former prevalence of marine conditions in one basin simultaneously with fluviatile or lacustrine in the other, and sometimes from the existence of land in one area causing a break or absence of all records during a period when deposits may have been in progress in the other basin. As bearing on this subject, it may be stated that we have unquestionable evidence of oscillations of level shown by the superposition of salt or brackish-water strata to fluviatile beds; and those of deep-sea origin to strata formed in shallow water. Even if the upward and downward movements were uniform in amount and direction, which is very improbable, their effect in producing the conversion of sea into land or land into sea would be different, according to the previous shape and varying elevation of the land and bottom of the sea. Lastly, denudation, marine and subaerial, has frequently caused the absence of deposits in one basin of corresponding age to those in the other, and this destructive agency has been more than ordinarily effective on account of the loose and unconsolidated nature of the sands and clays.
UPPER EOCENE OF ENGLAND.
BEMBRIDGE SERIES, A.1.
These beds are about 120 feet thick, and, as stated in Chapter 15, lie immediately under the Hempstead beds, near Yarmouth, in the Isle of Wight, being conformable with those Lower Miocene strata. They consist of marls, clays, and limestones of fresh-water, brackish, and marine origin. Some of the most abundant shells, as Cyrena semistriata var., and Paludina lenta, Figure 163 Chapter 15, are common to this and to the overlying Hempstead series; but the majority of the species are distinct. The following are the subdivisions described by the late Professor Forbes:
(FIGURE 165. Melania turritissima, Forbes. Bembridge.)
a. Upper marls, distinguished by the abundance of Melania turritissima, Forbes (Figure 165).
(FIGURE 166. Fragment of carapace of Trionyx. Bembridge Beds, Isle of Wight.)
b. Lower marls, characterised by Cerithium mutabile, Cyrena pulchra, etc., and by the remains of Trionyx (see Figure 166).
c. Green marls, often abounding in a peculiar species of oyster, and accompanied by Cerithium, Mytilus, Arca, nucula, etc.)
(FIGURE 167. Bulimus ellipticus, Sowerby. Bembridge Limestone. 1/2 natural size.)
(FIGURE 168. Helix occlusa, Edwards. Bembridge Limestone, Isle of Wight.)
(FIGURE 169. Paludina orbicularis. Bembridge.)
(FIGURE 170. Planorbis discus, Edwards. Bembridge. 1/2 diameter.)
(FIGURE 171. Lymnea longiscata, Brand. Natural size.)
(FIGURE 172. Chara tuberculata, seed-vessel. Bembridge Limestone, Isle of Wight.)
d. Bembridge limestones, compact cream-coloured limestones alternating with shales and marls, in all of which land-shells are common, especially at Sconce, near Yarmouth, as described by Mr. F. Edwards. The Bulimus ellipticus, Figure 167, and Helix occlusa, Figure 168, are among its best known land-shells. Paludina orbicularis, Figure 169, is also of frequent occurrence. One of the bands is filled with a little globular Paludina. Among the fresh-water pulmonifera, Lymnea longiscata (Figure 171) and Planorbis discus (Figure 170) are the most generally distributed: the latter represents or takes the place of the Planorbis euomphalus (see Figure 175) of the more ancient Headon series. Chara tuberculata (Figure 172) is the characteristic Bembridge gyrogonite or seed-vessel.
(FIGURE 173. Anoplotherium commune. Binstead, Isle of Wight. Lower molar tooth, natural size.)
(FIGURE 174. Palaeotherium magnum, Cuvier.)
(FIGURE 175. Planorbis euomphalus, Sowerby. Headon Hill. 1/2 diameter.)
From this formation on the shores of Whitecliff Bay, Dr. Mantell obtained a fine specimen of a fan palm, Flabellaria Lamanonis, Brong., a plant first obtained from beds of corresponding age in the suburbs of Paris. The well-known building- stone of Binstead, near Ryde, a limestone with numerous hollows caused by Cyrenae which have disappeared and left the moulds of their shells, belongs to this subdivision of the Bembridge series. In the same Binstead stone Mr. Pratt and the Reverend Darwin Fox first discovered the remains of mammalia characteristic of the gypseous series of Paris, as Palaeotherium magnum (Figure 174), Palaeotherium medium, Palaeotherium minus, Palaeotherium minimum, Palaeotherium curtum, Palaeotherium crassum; also Anoplotherium commune (Figure 173), Anoplotherium secundarium, Dichobune cervinum, and Chaeropotamus Cuvieri. The Palaeothere above alluded to resembled the living tapir in the form of the head, and in having a short proboscis, but its molar teeth were more like those of the rhinoceros. Palaeotherium magnum was of the size of a horse, three or four feet high. The woodcut, Figure 174, is one of the restorations which Cuvier attempted of the outline of the living animal, derived from the study of the entire skeleton. As the vertical range of particular species of quadrupeds, so far as our knowledge extends, is far more limited than that of the testacea, the occurrence of so many species at Binstead, agreeing with fossils of the Paris gypsum, strengthens the evidence derived from shells and plants of the synchronism of the two formations.
OSBORNE OR ST. HELEN’S SERIES, A.2.
This group is of fresh and brackish-water origin, and very variable in mineral character and thickness. Near Ryde, it supplies a freestone much used for building, and called by Professor Forbes the Nettlestone grit. In one part ripple-marked flagstones occur, and rocks with fucoidal markings. The Osborne beds are distinguished by peculiar species of Paludina, Melania, and Melanopsis, as also of Cypris and the seeds of Chara.
HEADON SERIES A.3.
These beds are seen both in Whitecliff Bay, Headon Hill, and Alum Bay, or at the east and west extremities of the Isle of Wight. The upper and lower portions are fresh-water, and the middle of mixed origin, sometimes brackish and marine. Everywhere Planorbis euomphalus, Figure 175, characterises the fresh-water deposits, just as the allied form, Planorbis discus, Figure 170, does the Bembridge limestone. The brackish-water beds contain Potamomya plana, Cerithium mutabile, and Potamides cinctus (Figure 37 Chapter 3), and the marine beds Venus (or Cytherea) incrassata, a species common to the Limburg beds and Gres de Fontainebleau, or the Lower Miocene series. The prevalence of salt-water remains is most conspicuous in some of the central parts of the formation.
(FIGURE 176. Helix labyrinthica, Say. Headon Hill, Isle of Wight; and Hordwell Cliff, Hants– also recent.)
(FIGURE 177. Neritina concava, Sowerby. Headon series.)
(FIGURE 178. Lymnea caudata, Edw. Headon series.)
(FIGURE 179. Cerithium concavum, Sowerby. Headon series.)
Among the shells which are widely distributed through the Headon series are Neritina concava (Figure 177), Lymnea caudata (Figure 178), and Cerithium concavum (Figure 179). Helix labyrinthica, Say (Figure 176), a land-shell now inhabiting the United States, was discovered in this series by Mr. Searles Wood in Hordwell Cliff. It is also met with in Headon Hill, in the same beds. At Sconce, in the Isle of Wight, it occurs in the Bembridge series, and affords a rare example of an Eocene fossil of a species still living, though, as usual in such cases, having no local connection with the actual geographical range of the species. The lower and middle portion of the Headon series is also met with in Hordwell Cliff (or Hordle, as it is often spelt), near Lymington, Hants. Among the shells which abound in this cliff are Paludina lenta and various species of Lymnea, Planorbis, Melania, Cyclas, Unio, Potamomya, Dreissena, etc.
Among the chelonians we find a species of Emys, and no less than six species of Trionyx; among the saurians an alligator and a crocodile; among the ophidians two species of land-snakes (Paleryx, Owen); and among the fish Sir P. Egerton and Mr. Wood have found the jaws, teeth, and hard shining scales of the genus Lepidosteus, or bony pike of the American rivers. This same genus of fresh-water ganoids has also been met with in the Hempstead beds in the Isle of Wight. The bones of several birds have been obtained from Hordwell, and the remains of quadrupeds of the genera Palaeotherium (Palaeotherium minus), Anoplotherium, Anthracotherium, Dichodon, Dichobune, Spalacodon, and Hyaenodon. The latter offers, I believe, the oldest known example of a true carnivorous animal in the series of British fossils, although I attach very little theoretical importance to the fact, because herbivorous species are those most easily met with in a fossil state in all save cavern deposits. In another point of view, however, this fauna deserves notice. Its geological position is considerably lower than that of the Bembridge or Montmartre beds, from which it differs almost as much in species as it does from the still more ancient fauna of the Lower Eocene beds to be mentioned in the sequel. It therefore teaches us what a grand succession of distinct assemblages of mammalia flourished on the earth during the Eocene period.
Many of the marine shells of the brackish-water beds of the above series, both in the Isle of Wight and Hordwell Cliff, are common to the underlying Barton Clay: and, on the other hand, there are some fresh-water shells, such as Cyrena obovata, which are common to the Bembridge beds, notwithstanding the intervention of the St. Helen’s series. The white and green marls of the Headon series, and some of the accompanying limestones, often resemble the Eocene strata of France in mineral character and colour in so striking a manner as to suggest the idea that the sediment was derived from the same region or produced contemporaneously under very similar geographical circumstances.
(FIGURE 180. Solenastraea cellulosa, Duncan. Brockenhurst.)
At Brockenhurst, near Lyndhurst, in the New Forest, marine strata have recently been found containing fifty-nine shells, of which many have been described by Mr. Edwards. These beds rest on the Lower Headon, and are considered as the equivalent of the middle part of the Headon series, many of the shells being common to the brackish-water or Middle Headon beds of Colwell and Whitecliff Bays, such as Cancellaria muricata, Sowerby, Fusus labiatus, Sowerby, etc. In these beds at Brockenhurst, corals, ably described by Dr. Duncan, have recently been found in abundance and perfection; see Figure 180, Solenastraea cellulosa.
Baron von Konen has pointed out that no less than forty-six out of the fifty- nine Brockenhurst shells, or a proportion of 78 per cent, agree with species occurring in Dumont’s Lower Tongrian formation in Belgium. (Quarterly Geological Journal volume 20 page 97 1864.) This being the case, we might fairly expect that if we had a marine equivalent of the Bembridge series or of the contemporaneous Paris gypsum, we should find it to contain a still greater number of shells common to the Tongrian beds of Belgium, but the exact correlation of these fresh-water groups of France, Belgium, and Britain has not yet been fully made out. It is possible that the Tongrian of Dumont may be newer than the Bembridge series, and therefore referable to the Lower Miocene. If ever the whole series should be complete, we must be prepared to find the marine equivalent of the Bembridge beds, or the uppermost Eocene, passing by imperceptible shades into the inferior beds of the overlying Miocene strata.
Among the fossils found in the Middle Headon are Cytherea incrassata and Cerithium plicatum (Figure 160 Chapter 15). These shells, especially the latter, are very characteristic of the Lower Miocene, and their occurrence in the Headon series has been cited as an objection to the line proposed to be drawn between Miocene and Eocene. But if we were to attach importance to such occasional passages, we should soon find that no lines of division could be drawn anywhere, for in the present state of our knowledge of the Tertiary series there will always be species common to beds above and below our boundary-lines.
BARTON SERIES (SANDS AND CLAYS), A.4 TABLE 16.1.)
(FIGURE 181. Chama squamosa, Eichw. Barton.)
Both in the Isle of Wight, and in Hordwell Cliff, Hants, the Headon beds, above- mentioned, rest on white sands usually devoid of fossils, and used in the Isle of Wight for making glass. In one of these sands Dr. Wright found Chama squamosa, a Barton Clay shell, in great plenty, and certain impressions of marine shells have been found in sands supposed to be of the same age in Whitecliff Bay. These sands have been called Upper Bagshot in the maps of our Government Survey, but this identification of a fossiliferous series in the Isle of Wight with an unfossiliferous formation in the London Basin can scarcely be depended upon. The Barton Clay, which immediately underlies these sands, is seen vertical in Alum Bay, Isle of Wight, and nearly horizontal in the cliffs of the mainland near Lymington. This clay, together with the Bracklesham beds, presently to be described, has been termed Middle Bagshot by the Survey. In Barton Cliff, where it attains a thickness of about 300 feet, it is rich in marine fossils.
It was formerly confounded with the London Clay, an older Eocene deposit of very similar mineral character, to be mentioned below, which contains many shells in common, but not more than one-fourth of the whole. In other words, there are known at present 247 species in the London Clay and 321 in that of Barton, and only 70 common to the two formations. Fifty-six of these have been found in the intermediate Bracklesham beds, and the reappearance of the other 14 may imply a return of similar conditions, whether of temperature or depth or of a muddy argillaceous bottom, common to the two periods of the London and Barton Clays. According to M. Hebert, the most characteristic Barton Clay fossils correspond to those of the Gres de Beauchamp, or Sables Moyens, of the Paris Basin, but it also contains many common to the older Calcaire Grossier.
SHELLS OF THE BARTON CLAY.
(FIGURE 182. Mitra scabra, Sowerby.)
(FIGURE 183. Voluta ambigua, Sol.)
(FIGURE 184. Typhis pungens, Brand.)
(FIGURE 185. Voluta athleta, Sol. Barton and Bracklesham.)
(FIGURE 186. Terebellum fusiforme, Lam. Barton and Bracklesham.)
(FIGURE 187. Terebellum sopita, Brand.)
(FIGURE 188. Cardita sulcata, Brand. Barton.)
(FIGURE 189. Crassatella sulcata, Sowerby. Bracklesham and Barton.)
(FIGURE 190. Nummulites variolaria, Lam. Var. of Nummulites radiata, Sowerby. Middle Eocene, Bracklesham Bay.
a. Natural size.
b. Magnified.)
Certain foraminifera called Nummulites begin, when we study the Tertiary formations in a descending order, to make their first appearance in these beds. A small species called Nummulites variolaria, Figure 190, is found both on the Hampshire coast and in beds of the same age in Whitecliff Bay, in the Isle of Wight. Several marine shells, such as Corbula pisum (Figure 158), are common to the Barton beds and the Hempstead or Lower Miocene series, and a still greater number, as before stated, are common to the Headon series.
MIDDLE EOCENE, ENGLAND.
BRACKLESHAM BEDS AND BAGSHOT SANDS (B.1, TABLE 16.1).
(FIGURE 191. Cardita (Venericardia) planicosta, Lam.)
(FIGURE 192. Nummulites (Nummularia) laevigata. Bracklesham. Dixon’s Fossils of Sussex, Plate 8.
a. Section of nummulite.
b. Group, with an individual showing the exterior of the shell.)
Beneath the Barton Clay we find in the north of the Isle of Wight, both in Alum and Whitecliff Bays, a great series of various coloured sands and clays for the most part unfossiliferous, and probably of estuarine origin. As some of these beds contain Cardita planicosta (Figure 191) they have been identified with the marine beds much richer in fossils seen in the coast section in Bracklesham Bay near Chichester in Sussex, where the strata consist chiefly of green clayey sands with some lignite. Among the Bracklesham fossils besides the Cardita, the huge Cerithium giganteum is seen, so conspicuous in the Calcaire Grossier of Paris, where it is sometimes two feet in length. The Nummulites laevigata (see Figure 192), so characteristic of the lower beds of the Calcaire Grossier in France, where it sometimes forms stony layers, as near Compiegne, is very common in these beds, together with Nummulites scabra and Nummulites variolaria. Out of 193 species of testacea procured from the Bagshot and Bracklesham beds in England, 126 occur in the Calcaire Grossier in France. It was clearly, therefore, coeval with that part of the Parisian series more nearly than with any other.
(FIGURE 193. Palaeophis typhoeus, Owen; an Eocene sea-serpent. Bracklesham. a, b. Vertebra, with long neural spine preserved. c. Two vertebrae articulated together.)
(FIGURE 194. Defensive spine of Ostracion. Bracklesham.)
(FIGURE 195. Dental plates of Myliobates Edwardsi. Bracklesham Bay. Dixon’s Fossils of Sussex, Plate 8.)
According to tables compiled from the best authorities by Mr. Etheridge, the number of mollusca now known from the Bracklesham beds in Great Britain is 393, of which no less than 240 are peculiar to this subdivision of the British Eocene series, while 70 are common to the Older London Clay, and 140 to the Newer Barton Clay. The volutes and cowries of this formation, as well as the lunulites and corals, favour the idea of a warm climate having prevailed, which is borne out by the discovery of a serpent, Palaeophis typhoeus (see Figure 193), exceeding, according to Professor Owen, twenty feet in length, and allied in its osteology to the Boa, Python, Coluber, and Hydrus. The compressed form and diminutive size of certain caudal vertebrae indicate so much analogy with Hydrus as to induce Professor Owen to pronounce this extinct ophidian to have been marine. (Palaeontological Society Monograph Reptiles part 2 page 61.) Among the companions of the sea-snake of Bracklesham was an extinct crocodile (Gavialis Dixoni, Owen), and numerous fish, such as now frequent the seas of warm latitudes, as the Ostracion of the family Balistidae, of which a dorsal spine is figured (see Figure 194), and gigantic rays of the genus Myliobates (see Figure 195).
(FIGURE 196. Carcharodon angustidens, Agassiz.)
(FIGURE 197. Otodus obliquus, Agassiz.)
(FIGURE 198. Lamna elegans, Agassiz.)
(FIGURE 199. Galeocerdo latidens, Agassiz.)
The teeth of sharks also, of the genera Carcharodon, Otodus, Lamna, Galeocerdo, and others, are abundant. (See Figures 196, 197, 198, 199.)
MARINE SHELLS OF BRACKLESHAM BEDS.
ALUM BAY AND BOURNEMOUTH BEDS. (LOWER BAGSHOT OF ENGLISH SURVEY), B.2, TABLE 16.1.)
(FIGURE 200. Pleurotoma attenuata, Sowerby.)
(FIGURE 201. Voluta Selseiensis, Edwards.)
(FIGURE 202. Turritella multisulcata, Lam.)
(FIGURE 203. Lucina serrata, Sowerby. Magnified.)
(FIGURE 204. Conus deperditus, Brug.)
To that great series of sands and clays which intervene between the equivalents of the Bracklesham Beds and the London Clay or Lower Eocene, our Government Survey has given the name of the Lower Bagshot sands, for they are supposed to agree in age with the inferior unfossiliferous sands of the country round Bagshot in the London Basin. This part of the series is finely exposed in the vertical beds of Alum bay, in the Isle of Wight, and east and west of Bournemouth, on the south coast of Hampshire. In some of the close and white compact clays of this locality, there are not only dicotyledonous leaves, but numerous fronds of ferns allied to Gleichenia which are well preserved with their fruit.
None of the beds are of great horizontal extent, and there is much cross- stratification in the sands, and in some places black carbonaceous seams and lignite. In the midst of these leaf-beds in Studland Bay, Purbeck shells of the genus Unio attest the fresh-water origin of the white clay.
No less than forty species of plants are mentioned by MM. de la Harpe and Gaudin from this formation in Hampshire, among which the Proteaceae (Dryandra, etc.) and the fig tribe are abundant, as well as the cinnamon and several other laurineae, with some papilionaceous plants. On the whole, they remind the botanist of the types of subtropical India and Australia. (Heer Climat et Vegetation du Pays Tertiaire page 172.)
Heer has mentioned several species which are common to this Alum Bay flora and that of Monte Bolca, near Verona, so celebrated for its fossil fish, and where the strata contain nummulites and other Middle Eocene fossils. He has particularly alluded to Aralia primigenia (of which genus a fruit has since been found by Mr. Mitchell at Bournemouth), Daphnogene Veronensis, and Ficus granadilla, as among the species common to and characteristic of the Isle of Wight and Italian Eocene beds; and he observes that in the flora of this period these forms of a temperate climate which constitute a marked feature in the European Miocene formations, such as the willow, poplar, birch, alder, elm, hornbeam, oak, fir, and pine, are wanting. The American types are also absent, or much more feebly represented than in the Miocene period, although fine specimens of the fan-palm (Sabal) have been found in these Eocene clays at Studland. The number of exotic forms which are common to the Eocene and Miocene strata of Europe, like those to be alluded to in the sequel which are common to the Eocene and Cretaceous fauna, demonstrate the remoteness of the times in which the geographical distribution of living plants originated. A great majority of the Eocene genera have disappeared from our temperate climates, but not the whole of them; and they must all have exerted some influence on the assemblages of species which succeeded them. Many of these last occurring in the Upper Miocene are indeed so closely allied to the flora now surviving as to make it questionable, even in the opinion of naturalists opposed to the doctrine of transmutation, whether they are not genealogically related the one to the other.
LOWER EOCENE FORMATIONS, ENGLAND.
LONDON CLAY (C.1, TABLE 16.1).
This formation underlies the preceding, and sometimes attains a thickness of 500 feet. It consists of tenacious brown and bluish-grey clay, with layers of concretions called septaria, which abound chiefly in the brown clay, and are obtained in sufficient numbers from sea-cliffs near Harwich, and from shoals off the coast of Essex and the Isle of Sheppey, to be used for making Roman cement. The total number of British fossil mollusca known at present (January, 1870) in this formation are 254, of which 166 are peculiar, or not found in other Eocene beds in this country. The principal localities of fossils in the London clay are Highgate Hill, near London, the Island of Sheppey at the mouth of the Thames, and Bognor on the Sussex coast. Out of 133 fossil shells, Mr. Prestwich found only 20 to be common to the Calcaire Grossier (from which 600 species have been obtained), while 33 are common to the “Lits Coquilliers” (see below), in which 200 species are known in France.
In the Island of Sheppey near the mouth of the Thames, the thickness of the London Clay is estimated by Mr. Prestwich to be more than 500 feet, and it is in the uppermost 50 feet that a great number of fossil fruits were obtained, being chiefly found on the beach when the sea has washed away the clay of the rapidly wasting cliffs.
(FIGURE 205. Nipadites ellipticus, Bowerbank. Fossil fruit of palm, from Sheppey.)
Mr. Bowerbank, in a valuable publication on these fossil fruits and seeds, has described no less than thirteen fruits of palms of the recent type Nipa, now only found in the Molucca and Philippine Islands, and in Bengal (see Figure 205). In the delta of the Ganges, Dr. Hooker observed the large nuts of Nipa fruticans floating in such numbers in the various arms of that great river, as to obstruct the paddle-wheels of steamboats. These plants are allied to the cocoanut tribe on the one side, and on the other to the Pandanus, or screw-pine. There are also met with three species of Anona, or custard-apple; and cucurbitaceous fruits (of the gourd and melon family), and fruits of various species of Acacia.
Besides fir-cones or fruit of true Coniferae there are cones of Proteaceae in abundance, and the celebrated botanist the late Robert Brown pointed out the affinity of these to the New Holland types Petrophila and Isopogon. Of the first there are about fifty, and of the second thirty described species now living in Australia.
(FIGURE 206. Eocene Proteaceous Fruit. Petrophiloides Richardsoni. London Clay, Sheppey. Natural size. a. Cone.