CHAPTER XIV.

OLDER PLIOCENE AND MIOCENE FORMATIONS.

Strata of Suffolk termed Red and Coralline crag--Fossils, and proportion of recent species--Depth of sea and climate--Reference of Suffolk crag to the older Pliocene period--Migration of many species of shells southwards during the glacial period--Fossil whales--Sub- apennine beds--Asti, Sienna, Rome--Miocene formations--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--Miocene strata of Bordeaux and Piedmont--Molasse of Switzerland--Tertiary strata of Lisbon--Older Pliocene and Miocene formations in the United States--Sewalik Hills in India.

The older Pliocene strata, which next claim our attention, are chiefly confined, in Great Britain, to the eastern part of the county of Suffolk, where, like the Norwich beds already described, they are called "Crag," a provincial name given particularly to those masses of shelly sand which have been used from very ancient times in agriculture, to fertilize soils deficient in calcareous matter. The relative position of the "red crag" in Essex to the London clay, may be understood by reference to the accompanying diagram (fig. 142.).

These deposits, judging by the shells which they contain, appear, according to Professor Edward Forbes, to have been formed in a sea of moderate depth, generally from 15 to 25 fathoms deep, although in some few spots perhaps deeper. But they may, nevertheless, have been accumulated at the distance of 40 or 50 miles from land.

The Suffolk crag is divisible into two masses, the upper of which has been termed the Red, and the lower the Coralline Crag.[162-A] The upper deposit consists chiefly of quartzose sand, with an occasional intermixture of shells, for the most part rolled, and sometimes comminuted. The lower or Coralline crag is of very limited extent, ranging over an area about 20 miles in length, and 3 or 4 in breadth, between the rivers Alde and Stour. It is generally calcareous and marly--a mass of shells and small corals, passing occasionally into a soft building stone. At Sudbourn, near Orford, where it assumes this character, are large quarries, in which the bottom of it has not been reached at the depth of 50 feet. At some places in the neighbourhood, the softer mass is divided by thin flags of hard limestone, and corals placed in the upright position in which they grew.

The Red crag is distinguished by the deep ferruginous or ochreous colour of its sands and fossils, the Coralline by its white colour. Both formations are of moderate thickness; the red crag rarely exceeding 40, and the coralline seldom amounting to 20, feet. But their importance is not to be estimated by the density of the mass of strata or its geographical extent, but by the extraordinary richness of its organic remains, belonging to a very peculiar type, which seems to characterize the state of the living creation in the north of Europe during the older Pliocene era.

For a large collection of the fish, echinoderms, shells, and corals of the deposits in Suffolk, we are indebted to the labours of Mr. Searles Wood. Of testacea alone he has obtained from 230 species from the Red, and 345 from the Coralline crag, about 150 being common to each. The proportion of recent species in the new group is considered by Mr. Wood to be about 70[162-B] per cent., and that in the older or coralline about 60. When I examined these shells of Suffolk in 1835, with the assistance of Dr. Beck, Mr. George Sowerby, Mr. Searles Wood, and other eminent conchologists, I came to the opinion that the extinct species predominated very decidedly in number over the living. Recent investigations, however, have thrown much new light on the conchology of the Arctic, Scandinavian, British, and Mediterranean Seas. Many of the species formerly known only as fossils of the Crag, and supposed to have died out, have been dredged up in a living state from depths not previously explored. Other recent species, before regarded as distinct from the nearest allied Crag fossils, have been observed, when numerous individuals were procured, to be liable to much greater variation, both in size and form, than had been suspected, and thus have been identified. Consequently, the Crag fauna has been found to approach much more nearly to the recent fauna of the Northern, British, and Mediterranean Seas than had been imagined. The analogy of the whole group of testacea to the European type is very marked, whether we refer to the large development of certain genera in number of species or to their size, or to the suppression or feeble representation of others. The indication also afforded by the entire fauna of a climate not much warmer than that now prevailing in corresponding latitudes, prepares us to believe that they are not of higher antiquity than the Older Pliocene era.[163-A]

The position of the red crag in Essex to the subjacent London clay and chalk has been already pointed out (fig. 142.). Whenever the two divisions are met with in the same district, the red crag lies uppermost; and, in some cases, as in the section represented in fig. 143., it is observed that the older or coralline mass _b_ had suffered denudation before the newer formation _a_ was thrown down upon it. At D there is not only a distinct cliff, 8 or 10 feet high, of coralline crag, running in a direction N.E. and S.W., against which the red crag abuts with its horizontal layers; but this cliff occasionally overhangs. The rock composing it is drilled everywhere by _Pholades_, the holes which they perforated having been afterwards filled with sand and covered over when the newer beds were thrown down. As the older formation is shown by its fossils to have accumulated in a deeper sea (15, and sometimes 25, fathoms deep or more), there must no doubt have been an upheaval of the sea-bottom before the cliff here alluded to was shaped out. We may also conclude that so great an amount of denudation could scarcely take place, in such incoherent materials, without many of the fossils of the inferior beds becoming mixed up with the overlying crag, so that considerable difficulty must be occasionally experienced by the palaeontologist in deciding which species belong severally to each group. The red crag being formed in a shallower sea, often resembles in structure a shifting sand bank, its layers being inclined diagonally, and the planes of stratification being sometimes directed in the same quarry to the four cardinal points of the compass, as at Butley. That in this and many other localities, such a structure is not deceptive or due to any subsequent concretionary re-arrangement of particles, or to mere lines of colour, is proved by each bed being made up of flat pieces of shell which lie parallel to the planes of the smaller strata.

Some fossils, which are very abundant in the red crag, have never been found in the white or coralline division; as, for example, the _Fusus contrarius_ (fig. 144.), and several species of _Buccinum_ (or _Nassa_) and _Murex_ (see figs. 145, 146.), which two genera seem wanting in the lower crag.

[4 Illustrations: Fossils characteristic of the Red Crag.

Fig. 144. _Fusus contrarius._

Fig. 145. _Murex alveolatus._

Fig. 146. _Nassa granulata._

Fig. 147. _Cypraea coccinelloides._

Fig. 144. half nat. size; the others nat. size.]

Among the bones and teeth of fishes are those of large sharks (_Carcharias_), and a gigantic skate of the extinct genus _Myliobates_, and many other forms, some common to our seas, and many foreign to them.

The distinctness of the fossils of the coralline crag arises in part from higher antiquity, and, in some degree, from a difference in the geographical conditions of the submarine bottom. The prolific growth of corals, echini, and a prodigious variety of testacea, implies a region of deeper and more tranquil water; whereas, the red crag may have formed afterwards on the same spot, when the water was shallower. In the mean time the climate may have become somewhat cooler, and some of the zoophytes which flourished in the first period may have disappeared, so that the fauna of the red crag acquired a character somewhat more nearly resembling that of our northern seas, as is implied by the large development of certain sections of the genera _Fusus_, _Buccinum_, _Purpura_, and _Trochus_, proper to higher latitudes, and which are wanting or feebly represented in the inferior crag.

Some of the corals of the lower crag of Suffolk belong to genera unknown in the living creation, and of a very peculiar structure; as, for example, that represented in the annexed fig. (148.), which is one of several species having a globular form. The great number and variety of these zoophytes probably indicate an equable climate, free from intense cold in winter. On the other hand, that the heat was never excessive is confirmed by the prevalence of northern forms among the testacea, such as the _Glycimeris_, _Cyprina_, and _Astarte_. Of the genus last mentioned (see fig. 149.) there are about fourteen species, many of them being rich in individuals; and there is an absence of genera peculiar to hot climates, such as _Conus_, _Oliva_, _Mitra_, _Fasciolaria_, _Crassatella_, and others. The cowries (_Cypraea_, fig. 147.), also, are small, and belong to a section (_Trivia_) now inhabiting the colder regions. A large volute, called _Voluta Lamberti_ (fig. 150.), may seem an exception; but it differs in form from the volutes of the torrid zone, and may, like the living _Voluta Magellanica_, have been fitted for an extra-tropical climate.

The occurrence of a species of _Lingula_ at Sutton is worthy of remark, as these _Brachiopoda_ seem now confined to more equatorial latitudes, and the same may be said still more decidedly of a species of _Pyrula_, allied to _P. reticulata_. Whether, therefore, we may incline to the belief that the mean annual temperature was higher or lower than now, we may at least infer that the climate and geographical conditions were by no means the same at the period of the Suffolk crag as those now prevailing in the same region.

Of the echinoderms of the coralline crag about eleven species are known, but some of these are in too fragmentary a condition to admit of exact comparison. Of six which are the most perfect, Prof. E. Forbes has been able to identify three with recent species: one of which, of the genus _Echinus_, is British; a second, _Echinocyamus_, British and Mediterranean; and a third, _Echinus monilis_, a Mediterranean species, also found fossil in the faluns of Touraine.

One of the most interesting conclusions deduced from a careful comparison of the shells of these British Older Pliocene strata and those now inhabiting our seas, has been pointed out by Prof. E. Forbes. It appears that, during the glacial period, a period intermediate, as we have seen, between that of the crag and our own times, many shells, previously established in the temperate zone, retreated southwards to avoid an uncongenial climate. The Professor has given a list of fifty shells which inhabited the British seas while the coralline and red crag were forming, and which are wanting in the Pleistocene or glacial deposits. They must, therefore, after their migration to the south, have made their way northwards again. In corroboration of these views, it is stated that all these fifty species occur fossil in the Newer Pliocene strata of Sicily, Southern Italy, and the Grecian Archipelago, where they may have enjoyed, during the era of floating icebergs, a climate resembling that now prevailing in higher European latitudes.[166-A]

In the red crag at Felixstow, in Suffolk, Professor Henslow has found the ear-bones of no less than four species of cetacea, which, according to Mr. Owen, are the remains of true whales of the family _Balaenidae_. Mr. Wood is of opinion that these cetacea may be of the age of the red crag, or if not that they may be derived from the destruction of beds of coralline crag. I agree with him that the supposition of their having been washed out of the London clay, in which no _Balaenidae_ have yet been met with, is improbable.

Strata containing fossil shells, like those of the Suffolk crag, above described, have been found at Antwerp, and on the banks of the Scheldt below that city. In 1840 I observed a small patch of them near Valognes, in Normandy; and there is also a deposit containing similar fossils at St. George Bohon, and several places a few leagues to the S. of Carentan, in Normandy; but they have never been traced farther southwards.

_Subapennine strata._--The Apennines, it is well known, are composed chiefly of secondary rocks, forming a chain which branches off from the Ligurian Alps and passes down the middle of the Italian peninsula. At the foot of these mountains, on the side both of the Adriatic and the Mediterranean, are found a series of tertiary strata, which form, for the most part, a line of low hills occupying the space between the older chain and the sea. Brocchi, as we have seen (p. 105.), was the first Italian geologist who described this newer group in detail, giving it the name of the Subapennines; and he classed all the tertiary strata of Italy, from Piedmont to Calabria, as parts of the same system. Certain mineral characters, he observed, were common to the whole; for the strata consist generally of light brown or blue marl, covered by yellow calcareous sand and gravel. There are also, he added, some species of fossil shells which are found in these deposits throughout the whole of Italy.

We have now, however, satisfactory evidence that the Subapennine beds of Brocchi belong, at least, to three periods. To the Miocene we can refer a portion of the strata of Piedmont, those of the hill of the Superga, for example; to the Older Pliocene, part of the strata of northern Italy, of Tuscany, and of Rome; while the tufaceous formations of Naples, of Ischia, and the calcareous strata of Otranto, are referable to the Newer Pliocene, and in great part to the Post-Pliocene period.

That there is a considerable correspondence in the mineral composition of these different Italian groups is undeniable; but not that exact resemblance which should lead us to assume a precise identity of age, unless the fossil remains agreed very closely. It is now indispensable that a new scrutiny should be made in each particular district, of the fossils derived from the upper and lower beds--especially such localities as Asti and Parma, where the formation attains a great thickness; and at Sienna, where the shells of the incumbent yellow sand are generally believed to approach much more nearly, as a whole, to the recent fauna of the Mediterranean than those in the subjacent blue marl.

The greyish brown or blue marl of the Subapennine formation is very aluminous, and usually contains much calcareous matter and scales of mica. Near Parma it attains a thickness of 2000 feet, and is charged throughout with marine shells, some of which lived in deep, others in shallow water, while a few belong to freshwater genera, and must have been washed in by rivers. Among these last I have seen the common _Limnea palustris_ in the blue marl, filled with small marine shells. The wood and leaves, which occasionally form beds of lignite in the same deposit, may have been carried into the sea by similar causes. The shells, in general, are soft when first taken from the marl, but they become hard when dried. The superficial enamel is often well preserved, and many shells retain their pearly lustre, part of their external colour, and even the ligament which unites the valves. No shells are more usually perfect than the microscopic foraminifera, which abound near Sienna, where more than a thousand full-grown individuals may be sometimes poured out of the interior of a single univalve of moderate dimensions.

The other member of the Subapennine group, the yellow sand and conglomerate, constitutes, in most places, a border formation near the junction of the tertiary and secondary rocks. In some cases, as near the town of Sienna, we see sand and calcareous gravel resting immediately on the Apennine limestone, without the intervention of any blue marl. Alternations are there seen of beds containing fluviatile shells, with others filled exclusively with marine species; and I observed oysters attached to many limestone pebbles. This appears to have been a point where a river, flowing from the Apennines, entered the sea when the tertiary strata were formed.

The sand passes in some districts into a calcareous sandstone, as at San Vignone. Its general superposition to the marl, even in parts of Italy and Sicily where the date of its origin is very distinct, may be explained if we consider that it may represent the deltas of rivers and torrents, which gained upon the bed of the sea where blue marl had previously been deposited. The latter, being composed of the finer and more transportable mud, would be conveyed to a distance, and first occupy the bottom, over which sand and pebbles would afterwards be spread, in proportion as rivers pushed their deltas farther outwards. In some large tracts of yellow sand it is impossible to detect a single fossil, while in other places they occur in profusion. Occasionally the shells are silicified, as at San Vitale, near Parma, from whence I saw two individuals of recent species, one freshwater and the other marine (_Limnea palustris_, and _Cytherea concentrica_, Lam.), both perfectly converted into flint.

_Rome._--The seven hills of Rome are composed partly of marine tertiary strata, those of Monte Mario, for example, of the Older Pliocene period, and partly of superimposed volcanic tuff, on the top of which are usually cappings of a fluviatile and lacustrine deposit. Thus, on Mount Aventine, the Vatican, and the Capitol, we find beds of calcareous tufa with incrusted reeds, and recent terrestrial shells, at the height of about 200 feet above the alluvial plain of the Tiber. The tusk of the mammoth has been procured from this formation, but the shells appear to be all of living species, and must have been embedded when the summit of the Capitol was a marsh, and constituted one of the lowest hollows of the country as it then existed. It is not without interest that we thus discover the extremely recent date of a geological event which preceded an historical era so remote as the building of Rome.

MIOCENE FORMATIONS.

_Faluns of Touraine._--The Miocene strata, corresponding with those named by many geologists "Middle Tertiary," will next claim our attention. Near the towns of Dinan and Rennes, in Brittany, and again in the provinces bordering the Loire, a tertiary formation, containing another assemblage of fossils, is met with, to which the name of _Faluns_ has been long given by the French agriculturists, who spread the shelly sand and marl over the land, in the same manner as the crag was formerly much used in Suffolk. Isolated masses of these faluns occur from near the mouth of the Loire, near Nantes, as far 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. I have visited all the localities above mentioned, and found the beds 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, 10 miles S.W. of Saumur, they form a soft building-stone, chiefly composed of an aggregate of broken shells, 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, clay-slate, and various secondary formations, including the chalk; and, lastly, upon the upper freshwater limestone of the Parisian tertiary series, which, as before mentioned (p. 106.), stretches continuously from the basin of the Seine to that of the Loire.

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_ (fig. 45. p. 30.) is the most abundant. Remains of terrestrial quadrupeds are here and there intermixed, belonging to the genera Deinotherium, Mastodon, Rhinoceros, Hippopotamus, Chaeropotamus, 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 10 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 _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 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 20 miles south of Tours; and at Savigne, about 15 miles north-west of that place; 72 only could be identified with recent species, which is in the proportion of 25 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 mollusca from the faluns, in my possession, is 302, of which 45 only were found by Mr. Wood to be common to the Suffolk crag. The number of corals obtained by me at Doue, and other localities before adverted to, amounts to 43, as determined by Mr. Lonsdale, of which 7 agree specifically with those of the Suffolk crag. Only one has, as yet, been identified with a living species. But it is difficult, if not impossible, to institute at present a satisfactory comparison between fossil and recent _Polyparia_, from the deficiency of our knowledge of the living species. Some of the genera occurring fossil in Touraine, as the _Astrea_, _Lunulites_, and _Dendrophyllia_, have not been found in European seas north of the Mediterranean; nevertheless the _Polyparia_ 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, 45 only were found to be common to both, which is in the proportion of only 15 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, 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 70 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.

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 57 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 neighbouring 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 many of them, like the associated extinct testacea, are much less European in character, and point to the prevalence of a warmer climate,--in other words, to a state of things receding farther from the present condition of Europe, geographically and climatologically, and doubtless, therefore, receding farther in time.

_Bordeaux._--A great extent of country between the Pyrenees and the Gironde is overspread by tertiary deposits, which have been more particularly studied in the environs of Bordeaux and Dax, from whence about 700 species of shells have been obtained. A large proportion of these shells belong to the same zoological type as those of Touraine; but many are peculiar, and the whole may possibly constitute a somewhat older division of the Miocene period than the faluns of the Loire. We must wait, however, for farther investigations, in order to decide this question with accuracy.

_Piedmont._--Many of the shells peculiar to the hill of the Superga, near Turin, agree with those found at Bordeaux and Dax; but the proportion of recent species is much less. The strata of the Superga consist of a bright green sand and marl, and a conglomerate with pebbles, chiefly of green serpentine, and are inclined at an angle of more than 70 deg.. This formation, which attains a great thickness in the valley of the Bormida, is probably one of the oldest Miocene groups hitherto discovered.

_Molasse of Switzerland._--If we cross the Alps, and pass from Piedmont to Savoy, we find there, at the northern base of the great chain, and throughout the lower country of Switzerland, a soft green sandstone much resembling some of the beds of the basin of the Bormida, above described, and associated in a similar manner with marls and conglomerate. This formation is called in Switzerland "molasse," said to be derived from "mol," "_soft_" because the stone is easily cut in the quarry. It is of vast thickness, and probably divisible into several formations. How large a portion of these belong to the Miocene period cannot yet be determined, as fossil shells are often entirely wanting. In some places a decided agreement of the fossil fishes of the molasse and faluns has been observed. Among those common to both, M. Agassiz pointed out to me _Lamna contortidens_, _Myliobates Studeri_, _Spherodus cinctus_, _Notidanus primigenius_, and others.

_Lisbon._--Marine tertiary strata near Lisbon contain shells which agree very closely with those of Bordeaux, and are therefore referred to the Miocene era. Thus, out of 112 species collected by Mr. Smith of Jordanhill, between 60 and 70 were found to be common to the strata of Bordeaux and Dax, the recent species being in the proportion of 21 per cent.

_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, and Delaware, more modern strata predominate, which I have assimilated in age to the English crag and Faluns of Touraine.[172-A] If, chronologically speaking, they can be truly said to be the representatives of these two European formations, they may range in age from the Older Pliocene to the Miocene epoch, according to the classification of European strata adopted in this chapter.

The proportion of fossil shells agreeing with recent, out of 147 species collected by me, amounted to about 17 per cent., or one-sixth of the whole; but as the fossils so assimilated were almost always the same as species now living in the neighbouring Atlantic, the number may hereafter be augmented, when the recent fauna of that ocean is better known. In different localities, also, the proportion of recent species varied considerably.

On the banks of the James River, in Virginia, about 20 miles below Richmond, in a cliff about 30 feet high, I observed yellow and white sands overlying an Eocene marl, just as the yellow sands of the crag lie on the blue London clay in Suffolk and Essex in England. In the Virginian sands, we find a profusion of an Astarte (_A. undulata_, Conrad), which resembles closely, and may possibly be a variety of, one of the commonest fossils of the Suffolk crag (_A. bipartita_); the other shells also, of the genera _Natica_, _Fissurella_, _Artemis_, _Lucina_, _Chama_, _Pectunculus_, and _Pecten_, are analogous 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 13 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 fig. 152.), and _Venus tridacnoides_, abundant in these same formations, but also some shells which, like _Fulgur carica_ of Say, and _F. canaliculatus_ (see fig. 151.), _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 the beginning of the present geographical distribution of mollusca dates back to a period as remote as that of the Miocene strata.

Of ten species of zoophytes which I procured on the banks of the James River, two were identical with species of the Faluns of Touraine. With respect to climate, Mr. Lonsdale regards 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.

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, and the Maltese tertiaries.

_India._--The freshwater deposits of the Sub-Himalayan or Sewalik Hills, described by Dr. Falconer and Captain Cautley, may perhaps be regarded as Miocene. Like the faluns of Touraine, they contain the Deinotherium and Mastodon. Whether any of the associated freshwater and land shells are of recent species is not yet determined. The occurrence in them of a fossil giraffe and hippopotamus, genera now only living in Africa, as well as of a camel, implies a geographical state of things very different from that now established in the same parts of India. The huge Sivatherium of the same era appears to have been a ruminating quadruped bigger than the rhinoceros, and provided with a large upper lip, or probably a short proboscis, and having two pair of horns, resembling those of antelopes. Several species of monkey belonged to the same fauna; and among the reptiles, several crocodiles, larger than any now living, and an enormous tortoise, _Testudo Atlas_, the curved shell of which measured 20 feet across.

FOOTNOTES:

[162-A] See paper by E. Charlesworth, Esq.; London and Ed. Phil. Mag. No. xxxviii. p. 81., Aug. 1835.

[162-B] See Monograph on the Crag Mollusca. Searles Wood, Paleont. Soc. 1848.

[163-A] In regarding the Suffolk crag, both red and coralline, as older Pliocene instead of Miocene, I am only returning to the classification adopted by me in the Principles and Elements of Geology up to the year 1838.

[166-A] E. Forbes, Mem. Geol. Survey, Gt. Brit., vol. i. 386.

[172-A] Proceedings of the Geol. Soc. vol. iv. part 3. 1845, p. 547.