The Tuscan blue marls of various localities, from which the abovementioned flora was obtained, have yielded 36 species of marine mollusca, in which 16, according to M. Karl Mayer, are recent.

Aralo-Caspian formations.-This name has been given by Sir R. Murchison and M. de Verneuil to the limestone and associated sandy beds of brackish-water origin, which have been traced over a very extensive area, surrounding the Caspian, Azof, and Aral Seas, and parts of the northern and western coasts of the Black Sea. The fossil shells are partly, freshwater, as Paludina, Neritina, &c., and partly marine, of the family Cardiacia and Mytili. The species are identical, in great part, with those now inhabiting the Caspian; and when not living, they are analogous to forms now found in the inland seas of Asia, rather than to oceanic types. The limestone rises occasionally to the height of several hundred feet above the sea, and is supposed to indicate the former existence of a vast inland sheet of brackish water as large as the Mediterranean, or larger.

The proportion of recent species agreeing with the fauna of the Caspian is so considerable, as to leave no doubt in the minds of the geologists above cited that this rock, also called by them the "Steppe Limestone," belongs to the Pliocene period.*

*Geol. of Russia, p. 279.

CHAPTER XIV.

MIOCENE PERIOD.

Upper Miocene strata of France-Faluns of Touraine-Depth of sea and littoral character of fauna-Tropical climate implied by the testacea-Proportion of recent species of shells-Faluns more ancient than the Suffolk Crag-Varieties of Voluta Lamberti peculiar to Faluns and to Suffolk Crag-The same species are common to more than one geological Period-Lower Miocene strata of France-Remarks on classification, and where to draw the line of separation between Miocene and Eocene strata-Relations of the Grès de Fontainebleau to the Faluns and to the Calcaire Grossier-Lower Miocene strata of Central France-Lacustrine strata of Auvergne-Indusial limestone-Fossil mammalia of the Limagne d'Auvergne-Freshwater strata of the Cantal-Its resemblance in some places to white chalk with flints-Proofs of gradual deposition-Miocene strata of Bordeaux and South of France-Upper Miocene strata of GersDryopithecus-Belgian and British Miocene formations-Edeghem beds near Antwerp-Diest sands of Belgium and contemporaneous iron-sands of North Downs-Upper Miocene beds of Belgium-Bolderberg-Lower Miocene strata of Kleyn Spawen-Hempstead beds, Isle of Wight-Bovey Tracey Lignites in Devonshire-Isle of Mull Leaf-beds-Miocene formations of GermanyMayence basin-Upper Miocene beds of Vienna basin-Lower Miocene of Croatia-Fossil Lepidoptera-Oligocene strata of Professor Beyrich-Miocene strata of Italy.

MIOCENE STRATA OF FRANCE.-UPPER MIOCENE FALUNS OF

TOURAINE.-MIOCENE FORMATIONS.

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. The latter were classed by me in former editions of this work as Upper Eocene, and the reasons which have induced me to alter this classification will be fully explained to the reader in this and the following chapter. The term "faluns" is given provincially by French agriculturists to shelly sand and marl spread over the land in Touraine, just as the "crag" was formerly much used to fertilize the soil in Suffolk. Isolated masses of such faluns occur from near the mouth of the Loire, in the neighborhood of Nantes, to as far inland as a district south of Tours. They are also found at Pontlevoy, on the Cher, about 70 miles above the junction of that river with the Loire, and 30 miles S.E. 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 Doué, in the department of Maine and Loire, 10 miles S. W. 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 50 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, clayslate, various secondary formations, including the chalk; and, lastly, upon the upper freshwater limestone of the Parisian tertiary series, which, as before mentioned (p. 183), stretches continuously from the basin of the Seine to that of the Loire.

Fig. 162 a.

At some points, as at Louans, south of Tours, the shells are stained of a ferruginous color, 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 (fig. 45, p. 30) is the most abundant. Remains of terrestrial quadrupeds are here and there intermixed, belonging to the genera Deinotherium (fig. 162 a), Mastodon, Rhinoceros, Hippopotamus, Chæropotamus, Dichobune, Deer, and others, and these are accompanied by cetacea, such as the Lamantine, Morse, Sea-Calf, and Dolphin, all of extinct species.

Professor E. Forbes, after studying the fossil testacea which I obtained from these beds, informs me that he has no doubt they 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 molluscous fauna of the "faluns" is on the whole much more littoral than that of the 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 Cypræa, 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 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, Bossée, and other villages twenty miles south of Tours; and at Savigné, about fifteen miles northwest 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 testaceous mollusca from the faluns, in my possession, is 302; of which forty-five only were found by Mr. Wood to be common to the Suffolk Crag. The number of corals, including bryozoa and zoantharia, obtained by me at Doué, 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. Only one has, as yet, been identified with a living species. But it is difficult, notwithstanding the advances recently made by MM. Dana, Milne Edwards, Haime, and Lonsdale, to institute a satisfactory comparison between recent and fossil zoantharia and bryozoa. Some of the genera occurring fossil in Touraine, as the Astrea, Dendrophyllia, 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 endeavored to reconcile this marked difference in species with the supposed coexistence 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, 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 southwards 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 cli

mate.

On a comparison of 280 Mediterranean shells with 600 British species, made for me by an experienced conchologist in 1841, 160 were found to be common to both collections, which is in the proportion of fifty-seven per cent., a fourfold greater specific resemblance than between the seas of the crag and the faluns, notwithstanding the greater geographical distance between England and the Mediterranean than between Suffolk and the Loire. The principal grounds, however, for referring the English crag to the Older Pliocene and the French faluns to the 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 neighboring seas, while the accompanying extinct species are of genera such as characterize 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.

Among the conspicuous shells which are common to the faluns of the Loire and the Suffolk Crag is the Voluta Lamberti, before mentioned, page 204. All 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 the annexed figures.

Pliocene.

Variety characteristic of Faluns Variety characteristic of Suffolk Crag.
of Touraine. Miocene.

Mr. Searles Wood has fully appreciated these constant differences, but has, I think, with propriety regarded the two forms as mere varieties, or races of one and the same species. It is remarkable, however, that the late Alcide d'Orbigny, who so often founded species on very fine distinctions, should have coincided in this view. It may, I think, be fairly assumed that he would not have done so had he not imagined the Suffolk Crag to be identical in age with the

* A. d'Orbigny, Cours Elémentaire de Paléontologie, vol. ii. pp. 793, 797, 1852.