The _Chondrites_ are, perhaps, fossil Algae, with thick, smooth branching fronds, pinnatifid, or divided into pairs, with smooth cylindrical divisions, and resembling _Chondrus_, _Dumontia_, and _Halymenia_ among living genera.

The _Sarga.s.sites_, finally, have been vaguely referred to the genus _Sarga.s.sum_, so abundant in tropical seas. These Algae are distinguished by a filiform, branched, or ramose stem, bearing foliaceous appendages, regular, often petiolate, and altogether like leaves, and globular vesicles, supported by a small stalk.

The rocks which actually represent the _Upper Cretaceous period_ divide themselves naturally into six series; but British and French geologists make some distinction: the former dividing them into 1, _Maestricht_ and _Faxoe_ beds, said not to occur in England; 2, _White Chalk_, with _flints_; 3, _White Chalk_, without _flint_s; 4, _Chalk Marl_; 5, _Upper Greensand_; and 6, _Gault_. The latter four are divided by foreign geologists into 1, _Turonian_; 2, _Senonian_; 3, _Danian_.

The _Gault_ is the lowest member of the Upper Cretaceous group. It consists of a bluish-black clay mixed with greensand, which underlies the Upper Greensand. Near Cambridge, where the Gault is about 200 feet thick, a layer of sh.e.l.ls, bones, and nodules, called the "Coprolite Bed," from nine inches to a foot thick, represents the Upper Greensand, and rests on the top of the Gault Clay. These nodules and fossils are extensively worked on account of the phosphatic matter they contain, and when ground and converted into superphosphate of lime they furnish a very valuable agricultural manure. The Gault attains a thickness of about 100 feet on the south-east coast of England. It extends into Devonshire, Mr. Sharpe considering the Black Down beds of that country as its equivalents. It shows itself in the Departments of the Pas-de-Calais, the Ardennes, the Meuse, the Aube, the Yonne, the Ain, the Calvados, and the Seine-Inferieure. It presents very many distinct mineral forms, among which two predominate: green sandstone and blackish or grey clays. It is important to know this formation, for it is at this level that the Artesian waters flow in the wells of Pa.s.sy and Grenelle, near Paris.

The _glaucous_ chalk, or Upper Greensand, which is represented typically in the departments of the Sarthe, of the Charente-Inferieure, of the Yonne and the Var, is composed of quartzose sand, clay, sandstone, and limestone. In this formation, at the mouth of the Charente, we find a remarkable bed, which has been described as a submarine forest. It consists of large trees with their branches imbedded horizontally in vegetable matter, containing kidney-shaped nodules of amber, or fossilised resin.

The _Turonian_ beds are so named because the province of Touraine, between Saumur and Montrichard, possesses the best-developed type of this strata. The mineralogical composition of the beds is a fine and grey marly chalk, as at Vitry-le-Francois; of a pure white chalk, with a very fine grain, slightly argillaceous, and poor in fossils, in the Departments of the Yonne, the Aube, and the Seine-Inferieure; granular tufaceous chalk, white or yellowish, mixed with spangles of mica, and containing Ammonites, in Touraine and a part of the Department of the Sarthe; white, grey, yellow, or bluish limestone, inclosing Hippurites and Radiolites. In England the Lower Chalk pa.s.ses also into Chalk Marl, with Ammonites, and then into beds known as the Upper Greensand, containing green particles of glauconite, mixed, in Hampshire and Surrey, with much calcareous matter. In the Isle of Wight this formation attains a thickness of 100 feet. The _Senonian_ beds take their name from the ancient _Senones_. The city of Sens is in the centre of the best-characterised portion of this formation; Epernay, Meudon, Sens, Vendome, Royau, Cognac, Saintes, are the typical regions of the formation in France. In the Paris basin, inclusive of the Tours beds, it attains a thickness of upwards of 1,500 feet, as was proved by the samples brought up, during the sinking of the Artesian well, at Grenelle, by the borings.

In its geographical distribution the Chalk has an immense range; fine Chalk of nearly similar aspect and composition being met with in all directions over hundreds of miles, alternating in its lower beds with layers of flints. In England the higher beds usually consist of a pure-white calcareous ma.s.s, generally too soft for building-stone, but sometimes pa.s.sing into a solid rock.

The _Danian_ beds, which occupy the summit of the scale in the Cretaceous formation, are finely developed at Maestricht, on the Meuse; and in the Island of Zeeland, belonging to Denmark; where they are represented by a slightly yellowish, compact limestone, quarried for the construction of the city of Faxoe. It is slightly represented in the Paris basin at Meudon, and Laversines, in the Department of the Oise, by a white and often rubbly limestone known as _pisolitic limestone_. In this formation _Ammonites Danicus_ is found. The yellowish sandy limestone of Maestricht is referred to the _Danian_ type. Besides Molluscs, Polyps, and Polyzoa (Bryozoa), this limestone contains remains of Fishes, Turtles, and Crocodiles. But what has rendered this rock so celebrated was that it contained the remains of the _great animal of Maestricht_, the Maesasaurus.

At the close of the geological period, whose natural physiognomy we have thus traced, Europe was still far from displaying the configuration which it now presents. A map of the period would represent the great basin of Paris (with the exception of a zone of Chalk), the whole of Switzerland, the greater part of Spain and Italy, the whole of Belgium, Holland, Prussia, Hungary, Wallachia, and Northern Russia, as one vast sheet of water. A band of Jura.s.sic rocks still connected France and England at Cherbourg--which disappeared at a later period, and caused the separation of the British Islands from what is now France.

[Ill.u.s.tration: Fig. 147.--Exogym conica. Upper Greensand and Gault, from Blackdown Hill.]

TERTIARY PERIOD.

A new organic creation makes its appearance in the Tertiary period; nearly all the animal life is changed, and what is most remarkable in this new development is the appearance, in larger numbers, of the great cla.s.s of Mammifera.

During the Primary period, Crustaceans and Fishes predominated in the animal kingdom; in the Secondary period the earth was a.s.signed to Reptiles; but during the Tertiary period the Mammals were kings of the earth; nor do these animals appear in small number, or at distant intervals of time; great numbers of these beings appear to have lived on the earth, and at the same moment; many of them being, so to say, unknown and undescribed.

If we except the Marsupials, the first created Mammals would appear to have been the Pachyderms, to which the Elephant belongs. This order of animals long held the first rank; it was almost the only representative of the Mammal during the first of the three periods which const.i.tute the Tertiary epoch. In the second and third periods Mammals appear of species which have now become extinct, and which were alike curious from their enormous proportions, and from the singularity of their structure.

Of the species which appeared during the latter part of the epoch, the greater number still exist. Among the new Reptiles, some Salamanders, as large as Crocodiles, and not very distinct from existing forms, are added to the animal creation during the three periods of the Tertiary epoch. Chelonians were abundant within the British area during the older epoch. During the same epoch Birds are present, but in much fewer numbers than the Mammalia; here songsters, there birds of prey, in other cases domestic--or, rather, some appear to wait the yoke and domestication from man, the future supreme lord of the earth.

The seas were inhabited by a considerable number of beings of all cla.s.ses, and nearly as varied as those now living; but we no longer find in the Tertiary seas those Ammonites, Belemnites, and Hippurites which peopled the seas and multiplied with such astonishing profusion during the Secondary period. Henceforth the testaceous Mollusca approximate in their forms to those of the present time. The older and newer Tertiary Series contain few peculiar genera. But genera now found in warmer climates were greatly developed within the British area during the earlier Tertiary times, and _species_ of cold climates mark the close of the later Tertiaries.

What occurs to us, however, as most remarkable in the Tertiary epoch is the prodigious increase of animal life; it seems as if it had then attained its fullest extension. Swarms of testaceous Mollusca of microscopic proportions--Foraminifera and Nummulites--must have inhabited the seas, crowding together in ranks so serried that the agglomerated remains of their sh.e.l.ls form, in some places, beds hundreds of feet thick. It is the most extraordinary display which has appeared in the whole range of creation.

Vegetation during the Tertiary period presents well-defined characteristics. The Tertiary flora approaches, and is sometimes nearly identical with, that of our days. The cla.s.s of dicotyledons shows itself there in its fullest development; it is the epoch of flowers. The surface of the earth is embellished by the variegated colours of the flowers and fruits which succeed them. The white spikes of the Gramineae display themselves upon the verdant meadows without limit; they seem provocative of the increase of Insects, which now singularly multiply.

In the woods crowded with flowering trees, with rounded tops, like our oak and birch, Birds become more numerous. The atmosphere, purified and disembarra.s.sed of the veil of vapour which has. .h.i.therto pervaded it, now permits animals with such delicate pulmonary organs to live and multiply their race.

During the Tertiary period the influence of the central heat may have ceased to make itself felt, in consequence of the increased thickness of the terrestrial crust. By the influence of the solar heat, climates would be developed in the various lat.i.tudes; the temperature of the earth would still be nearly that of our present tropics, and at this epoch, also, cold would begin to make itself felt at the poles.

Abundant rains would, however, continue to pour upon the earth enormous quant.i.ties of water, which would give rise to important rivers; new lacustrine deposits of fresh water were formed in great numbers; and rivers, by means of their alluvial deposits, began to form new land. It is, in short, during the Tertiary epoch that we trace an alternate succession of beds containing organic beings of marine origin, with others peculiar to fresh water. It is at the end of this period that continents and seas take their respective places as we now see them, and that the surface of the earth received its present form.

The Tertiary epoch, or series, embraces three very distinct periods, to which the names of _Eocene_, _Miocene_, and _Pliocene_ have been given by Sir Charles Lyell. The etymology of these names is derived--Eocene, from the Greek ???, _dawn_, and ?a????, _recent_; Miocene, from e???, _less_, ?a????, _recent_; and Pliocene, from p?e???, _more_, ?a????, _recent_; by which it is simply meant to express, that each of these periods contains a minor or greater proportion of recent species (of Testacea), or is more or less remote from the dawn of life and from the present time;[81] the expressions are in one sense forced and incorrect, but usage has consecrated them, and they have obtained universal currency in geological language, from their convenience and utility.

[81] Lyell's "Elements of Geology," p. 187.

[Ill.u.s.tration: Fig. 148.--Trigonia margaritacea. (Living form.)]

THE EOCENE PERIOD.

During this period _terra firma_ has vastly gained upon the domain of the sea; furrowed with streams and rivers, and here and there with great lakes and ponds, the landscape of this period presented the same curious mixture which we have noted in the preceding age, that is to say, a combination of the vegetation of the primitive ages with one a.n.a.logous to that of our own times. Alongside the birch, the walnut, the oak, the elm, and the alder, rise lofty palm-trees, of species now extinct, such as _Flabellaria_ and _Palmacites_; with many evergreen trees (Conifers), for the most part belonging to genera still existing, as the _firs_, the _pines_, the _yews_, the _cypresses_, the _junipers_, and the _thuyas_ or tree of life.

The _Cupanioides_, among the Sapindaceae; the _Cuc.u.mites_, among the Cucurbitaceae (species a.n.a.logous to our bryony), climb the trunks of great trees, and hang in festoons of aerial garlands from their branches.

The Ferns were still represented by the genera _Pecopteris_, by the _Taeniopteris_, _Asplenium_, _Polypodium_. Of the mosses, some _Hepaticas_ formed a humble but elegant and lively vegetation alongside the terrestrial and frequently ligneous plants which we have noted.

_Equiseta_ and _Charae_ would still grow in marshy places and on the borders of rivers and ponds.

It is not without some surprise that we observe here certain plants of our own epoch, which seem to have had the privilege of ornamenting the greater watercourses. Among these we may mention the Water Caltrop, _Trapa natans_, whose fine rosettes of green and dentated leaves float so gracefully in ornamental ponds, supported by their spindle-shaped petioles, its fruit a hard coriaceous nut, with four h.o.r.n.y spines, known in France as _water-chestnuts_, which enclose a farinaceous grain not unpleasant to the taste; the pond-weed, _Potamogeton_, whose leaves form thick tufts of green, affording food and shelter to the fishes; _Nympheaceae_, which spread beside their large round and hollow leaves, so admirably adapted for floating on the water, now the deep-yellow flowers of the _Nenuphar_ now the pure white flowers of the _Nymphaea_.

Listen to Lecoq, as he describes the vegetation of the period:--"The Lower Tertiary period," he says, "constantly reminds us of the tropical landscapes of the present epoch, in localities where water and heat together impress on vegetation a power and majesty unknown in our climates. The Algae, which have already been observed in the marine waters at the close of the Cretaceous period, represented themselves under still more varied forms, in the earlier Tertiary deposits, when they have been formed in the sea. Hepaticas and Mosses grew in the more humid places; many pretty Ferns, as _Pecopteris_, _Taeniopteris_, and the _Equisetum stellare_ (Pomel) vegetated in cool and humid places. The fresh waters are crowded with _Naiades_, _Chara_, _Potamogeton_, _Caulinites_, with _Zosterites_, and with _Halochloris_. Their leaves, floating or submerged, like those of our aquatic plants, concealed legions of Molluscs whose remains have also reached us.

"Great numbers of Conifers lived during this period. M. Brongniart enumerates forty-one different species, which, for the most part, remind us of living forms with which we are familiar--of Pines, Cypresses, Thuyas, Junipers, Firs, Yews, and Ephedra. Palms mingled with these groups of evergreen trees; the _Flabellaria Parisiensis_ of Brongniart, _F. raphifolia_ of Sternberg, _F. maxima_ of Unger; and some _Palmacites_, raised their widely-spreading crowns near the magnificent _Hightea_; Malvaceae, or _Mallows_, doubtless arborescent, as many among them, natives of very hot climates, are in our days.

"Creeping plants, such as the _Cuc.u.mites variabilis_ (Brongn.), and the numerous species of _Cupaniodes_--the one belonging to the Cucurbitaceae, and the other to the Sapindaceae--twined their slender stems round the trunks, doubtless ligneous, of various Leguminaceae.

"The family of Betulaceae of the order Cupuliferae show the form, then new, of _Quercus_, the Oak; the Juglandeae, and Ulmaceae mingle with the Proteaceae, now limited to the southern hemisphere. _Dermatophyllites_, preserved in amber, seem to have belonged to the family of the Ericineae, and _Tropa Arcturae_ of Unger, of the group nothereae, floated on the shallow waters in which grew the _Chara_ and the _Potamogeton_.

"This numerous flora comprises more than 200 known species, of which 143 belonged to the Dicotyledons, thirty-three to the Monocotyledons, and thirty-three to the Cryptogams.

"Trees predominate here as in the preceding period, but the great numbers of aquatic plants of the period are quite in accordance with the geological facts, which show that the continents and islands were intersected by extensive lakes and inland seas, while vast marine bays and arms of the sea penetrated deeply into the land."

[Ill.u.s.tration: Fig. 149.--Branch of Eucalyptus restored.]

It is moreover a peculiarity of this period that the whole of Europe comprehended a great number of those plants which are now confined to Australasia, and which give so strange an aspect to that country, which seems, in its vegetation, as in its animals, to have preserved in its warm lat.i.tudes the last vestiges of the organic creations peculiar to the primitive world. As a type of dicotyledonous trees of the epoch, we present here a restored branch of _Eucalyptus_ (Fig. 149), with its flowers. All the family of the Proteaceae, which comprehends the _Banksia_, the _Hakea_, the _Gerilea protea_, existed in Europe during the Tertiary period. The family of Mimosas, comprising the _Acacia_ and _Inga_, which in our age are only natives of the southern hemisphere, abounded in Europe during the same geological period. A branch of _Banksia_, with its fructification, taken from impressions discovered in rocks of the period, is represented in Fig. 150--it is different from any species of Banksia living in our days.

[Ill.u.s.tration: Fig. 150.--Fruit-branch of Banksia restored.]

Mammals, Birds, Reptiles, Fishes, Insects, and Molluscs, form the terrestrial fauna of the Eocene period. In the waters of the lakes, whose surfaces are deeply ploughed by the pa.s.sage of large Pelicans, lived Molluscs of varied forms, as _Physa_, _Limnaea_, _Planorbis_; and Turtles swam about, as _Trionyx_ and the _Emides_. Snipes made their retreat among the reeds which grew on the sh.o.r.e; sea-gulls skimmed the surface of the waters or ran upon the sands; owls hid themselves in the cavernous trunks of old trees; gigantic buzzards hovered in the air, watching for their prey; while heavy crocodiles slowly dragged their unwieldy bodies through the high marshy gra.s.ses. All these terrestrial animals have been discovered in England or in France, alongside the overthrown trunks of palm-trees. The temperature of these countries was then much higher than it is now. The Mammals which lived under the lat.i.tudes of Paris and London are only found now in the warmest countries of the globe.

The Pachyderms (from the Greek pa???, _thick_, de?a, _skin_) seem to have been amongst the earliest Mammals which appeared in the Eocene period, and they held the first rank from their importance in number of species as well as in size. Let us pause an instant over these Pachyderms. Their predominance over other fossil Mammals, which exceed considerably the number now living, is a fact much insisted on by Cuvier. Among them were a great number of intermediate forms, which we seek for in vain in existing genera. In fact, the Pachyderms are separated, in our days, by intervals of greater extent than we find in any other mammalian genera; and it is very curious to discover among the animals of the ancient world the broken link which connects the chain of these beings, which have for their great tomb the plaster-quarries of Paris, Montmartre and Pantin being their latest refuge.

Each block taken from those quarries encloses some fragment of a bone of these Mammals; and how many millions of these bones had been destroyed before attention was directed to the subject! The _Palaeotherium_ and the _Anoplotherium_ were the first of these animals which Cuvier restored; and subsequent discoveries of other fragments of the same animals have only served to confirm what the genius of the great naturalist divined.

His studies in the quarries of Montmartre gave the signal, as they became the model, for similar researches and restorations of the animals of the ancient world, all over Europe--researches which, in our age, have drawn geology from the state of infancy in which it languished, in spite of the magnificent and persevering labours of Steno, Werner, Hutton, and Saussure.

[Ill.u.s.tration: Fig. 151.--Palaeotherium magnum restored.]

The _Palaeotherium_, _Anoplotherium_, and _Xiphodon_ were herbivorous animals, which must have lived in great herds. They appear to have been intermediate, according to their organisation, between the Rhinoceros, the Horse, and the Tapir. There seem to have existed many species of them, of very different sizes. After the labours of Cuvier, nothing is easier than to represent the _Palaeotherium_ as it lived: the nose terminating in a muscular fleshy trunk, or rather snout, somewhat like that of the Tapir; the eye small, and displaying little intelligence; the head enormously large; the body squat, thick, and short; the legs short and very stout; the feet supported by three toes, enclosed in a hoof; the size, that of a large horse. Such was the great Palaeotherium, peaceful flocks of which must have inhabited the valleys of the plateau which surrounds the ancient basin of Paris; in the lacustrine formations of Orleans and Argenton; in the Tertiary formations of Issil and Puy-en-Velay, in the department of the Gironde; in the Tertiary formations near Rome; and in the beds of limestone[82] at the quarries of Binsted, in the Isle of Wight. Fig. 151 represents the great Palaeotherium, after the design, in outline, given by Cuvier in his work on _fossil bones_.

[82] This limestone belongs to the Bembridge beds, and forms part of the Fluvio-marine series. See "Survey Memoir on the Geology of the Isle of Wight," by H. W. Bristow.

[Ill.u.s.tration: Fig. 152.--Skull of Palaeotherium magnum.]

The discovery and re-arrangement of these and other forms, now swept from the face of the globe, are the n.o.blest triumphs of the great French zoologist, who gathered them, as we have seen, from heaps of confused fragments, huddled together pell-mell, comprising the bones of a great many species of animals of a former age of the world, all unknown within the historic period. The generic characters of Palaeotherium give them forty-four teeth, namely, twelve _molars_, two _canines_, and twenty-eight others, three toes, a short proboscis, for the attachment of which the bones of the nose were shortened, as represented in Fig.

153, leaving a deep notch below them. The molar teeth bear considerable resemblance to those of the Rhinoceros. In the structure of that part of the skull intended to support the short proboscis, and in the feet, the animal seems to have resembled the Tapir.

[Ill.u.s.tration: Fig. 153.--Skeletons of the Palaeotherium magnum (_a_) and minimum (_b_) restored.]