In 1842, the late Mr. Channing Pearce described, under the name of Belemnoteuthis antiquus, a naked (destitute of a shell,) cephalopod, which occurs in immense numbers in certain beds of the Oxford clay, especially at Christian Malford, in Wiltshire. This animal has at the lower apical part a conical osselet of a horny substance, and fibrous structure, enclosing a chambered siphunculated shell, which becomes gradually thinner at the upper part, and forms a cup-like receptacle, in which is placed the ink-bag. The soft body of an elongated oval form, with a pair of lateral palleal fins, two large sessile eyes, and with eight uncinated arms and a pair of long tentacula, are preserved in a more or less distinct and perfect state in several specimens that have lately been discovered. Mr. Channing Pearce, Mr. Cunnington, and other collectors of these interesting remains, were convinced that this cephalopod was entirely distinct from the animal to which the Belemnite belonged.

In 1844, Professor Owen laid before the Royal Society "A description of certain Belemnites preserved with a great proportion of their soft parts in the Oxford clay, at Christian Malford, Wilts."[84] In this memoir (for which one of the royal medals of the Society was awarded) the author describes as the soft parts of the Belemnite the remains of the animal which Mr. Channing Pearce had two years previously shown to belong to a different genus (Belemnoteuthis). Belying on the correctness of Professor Owen's views, I gave an abstract of this memoir in my "Medals of Creation," and stated that belemnites had been discovered with the osselet, receptacle, and ink-bag, in their natural position, and with remains of the mantle, body, fins, eyes, and the tentacula, with their horny rings and hooks.[85]

The discovery by my son (Mr. Reginald Neville Mantell) of some remarkably perfect specimens of belemnites in the Oxford clay, exposed in the railway works on which he was engaged, near Trowbridge, in Wilts, led me to examine the structure of the Belemnoteuthis with more attention than I had hitherto done, as well as the evidence adduced by Professor Owen in proof that the fossil osselet, the Belemnite, belonged to the same genus of cephalopoda. I found that no specimen had been obtained in which the phragmocone, or terminal chambered part of the Belemnoteuthis (of Pearce), was situated in the alveolus of a Belemnite; but Professor Owen having assumed that the osselet of the former must have originally been protected by a rostrum, or guard, described the soft parts as belonging to the animal of the Belemnite, conceiving that the phragmocone of the Belemnoteuthis was that of a Belemnite that had slipped out of the guard.

In a communication to the Royal Society, in 1848, I demonstrated how utterly at variance with the facts were these conclusions, and pointed out the essential distinctive characters that separated the two extinct genera, so far as the specimens then discovered would warrant.[86] Other illustrative examples of the Belemnite have since been obtained; and in a supplementary paper read before the Royal Society, February 14th, of the present year (1850), I have stated what appears to me to be the extent of our present knowledge of the organization of the Belemnite. I subjoin an abstract of that paper, which embodies the result of an examination of many hundred specimens of Belemnites and Belemnoteuthites. The annexed outline, or diagram, shows the known structures of the Belemnite; of the soft parts of the animal, a few imperfect carbonaceous traces, apparently of the mantle, around and between the shelly processes of the upper part of the phragmocone, are the only vestiges I have been able to detect. The most perfect Belemnite hitherto discovered consists of,

1. An external Capsule (e) which invested the osselet or sepiostaire, and extending upwards, constituted the external sheath of the receptacle.

2. The Osselet, characterized by its fibrous radiated structure, terminating distally in a solid rostrum or guard (i), having an alveolus, or conical hollow (g), to receive the apical portion of the chambered phragmocone, and expanding proximally into a thin cup, which became confluent with the capsule, and formed the receptacle (b, b,) for the viscera.

3. The Phragmocone (d), or chambered, siphunculated (c), internal shell; the apex of which occupied the alveolus (g) of the guard, and the upper part constituted a capacious chamber, from the basilar margin of which proceeded two long, flat, testaceous, processes (a, a,).

These structures comprise all that are at present known of the animal to which the fossil commonly called "Belemnite," belonged.

Of the Belemnoteuthis, the cephalopod which Professor Owen considers to be a Belemnite, many examples of the body with eight uncinated arms and a pair of long tentacula, and with an ink-bag, and palleal fins, have been discovered. The osselet of this animal, like that of the Belemnite, has a fibro-radiated structure, investing a conical chambered shell; but this organ, for reasons fully detailed in the memoir, could never have been contained within the alveolus of a Belemnite.

No certain evidence has been obtained of the occurrence of an ink-bag in natural connexion with a Belemnite.

Diagram of the known Structures of the Belemnites Puzosianus, from Trowbridge.

a, a, dorsal processes.

b, b, the receptacle.

c, c, the siphuncle.

d, d, the phragmocone.

e, the capsule.

f, the inferior end of the phragmocone.

g, the alveolus of the guard.

h, vertical section of the guard.

i, the guard, or rostrum of the osselet.

k, sulcus, or furrow, on the ventral aspect of this species of Belemnite.

l, capsule, or periostricum.

m, the dorsal line.

n, transverse section, showing the fibrous radiated structure of the guard.

In the annexed outline the several parts are represented in their natural relative positions. The capsule, or most external investment, (e) is seen only in section, being removed to expose the rostrum or guard (the fossil body generally known as the Belemnite). The upper three-fourths of the rostrum are also taken away, to show the phragmocone which it originally enveloped. The straight transverse lines denote the chambers of the phragmocone; the latter is seen extending downwards till it terminates in a point or apex; that part of the cavity in the guard is called the alveolus. The siphuncle, or tube which extends through the entire series of chambers, and is situated on the ventral margin, is indicated at c, c. The dorsal processes (a, a) are seen on their inner aspect at the upper part; the diverging lines (m) between them indicate the impressions of the soft parts, of which some traces remain.

III. Fossil Remains of Birds.—The Moa, or Dinornis of New Zealand. The bones of birds are of extreme rarity in a fossil state. Throughout the immense series of the palæozoic and secondary formations—the accumulated sedimentary deposits of innumerable ages—no unquestionable indications of the existence of this class of highly organized beings have been brought to light.

In the Triassic, or New Red argillaceous sandstones of the valley of the Connecticut River, in North America, some very remarkable phenomena have, however, been discovered, and which in the opinions of many eminent observers render it highly probable, that at the period when these strata were deposited, numerous birds, some of colossal magnitude, abounded on the then dry land. When slabs of these sandstones are split asunder, or exposed, so as to exhibit the sedimentary surface which separates one layer from another, the foot-prints of many species of bipeds are perceived deeply impressed on the stone, and disposed in such manner as to prove that they are the tracks of animals that walked over the surface of the deposit when it was in a soft or plastic state. The close analogy of these imprints to those of birds' feet, not only in their general resemblance, but also in the disposition of the tracks, and in the relation of the distance of the stride, and the depth and shallowness of the impressions, to the size of the respective feet, tends to corroborate the inference first enunciated by Professor Hitchcock, and subsequently confirmed by other geologists, that these mysterious markings on the rock, are natural records of the existence of various tribes of birds during the Triassic period;[87] but unfortunately the only certain evidence of the correctness of this opinion—remains of the skeletons—is wanting; not a vestige of a vertebrated animal of a higher class than fishes and reptiles has been discovered.[88]

In the vast fluviatile formation—the Wealden—of the south-east of England, which abounds in the remains of terrestrial plants and reptiles, many fragments of bones of such tenuity as to indicate that they belonged to animals capable of flight, have from time to time been collected since my first discovery and announcement, in 1822, of supposed birds' bones in the strata of Tilgate Forest. Some of these relics were declared by Baron Cuvier, and subsequently by Professor Owen, to be unquestionably those of birds; probably some species of waders. But recent observations have rendered it doubtful whether all the specimens of this class from the Wealden, like those from Stonesfield, are not to be regarded as referable to flying reptiles (Pterodactyles).[89]

In the chalk of Kent several bones of a very large flying animal have been obtained from a quarry at Burham, near Maidstone; some of these are figured and described in Professor Owen's beautiful work on British Fossil Mammals and Birds, as those of a bird allied to the Albatross; but the occurrence in the same quarry of jaws with teeth, and other undoubted remains of a gigantic Pterodactyle,[90] and the absence in the specimens figured of osteological characters exclusively ornithic, seem to support the conclusion that these also must be ascribed to flying reptiles.

In the most ancient tertiary strata unquestionable vestiges of birds occur; in the Sub-Himalaya eocene deposits, they are associated with bones of the extinct elephantine mammalia of India; in those of the Paris basin with the remains of the Palæotheria, &c. In the miocene and pliocene formations, the bones and even egg-shells of several species and genera have been detected. The remains of birds, however, even in comparatively recent deposits, were of such rare occurrence as to be ranked by the collector of fossils among the most precious of his acquisitions; but a few years ago, a most extraordinary discovery in our Antipodean colony. New Zealand, astonished and delighted the palæontologist, by placing before him hundreds of bones of numerous extinct genera of birds, some of which far exceed in magnitude those of the most gigantic living species, the Ostrich.

In various localities of the maritime districts of New Zealand, there had been observed in the beds of rivers and streams, fossil bones of birds of colossal magnitude, belonging to many species and several genera, associated with similar relics of smaller species. These bones had attracted the attention of the natives long ere the country was visited by Europeans; and traditions are rife among the New Zealanders that this race formerly existed in great numbers, and served as food to their remote ancestors. They also believe that some of the largest species have been seen alive within the memory of man; and even affirm that individuals still exist in the unfrequented and inaccessible parts of the interior of the country. They call the bird Moa, and state that its head and tail were adorned with magnificent plumes of feathers, which were worn by their ancient chiefs as ornaments of distinction.

Nine years since, a fragment of a thigh-bone of a bird larger than that of the Ostrich was brought to England by Mr. Rule, and submitted to the examination of Professor Owen, who pronounced it to belong to a gigantic bird of the Struthious (Ostrich) order. A few years afterwards several collections of vertebræ, bones of the extremities, &c. were transmitted to England by Messrs. Williams, Wakefield, Earle, &c., which corroborated that opinion, and proved that there formerly existed in the islands of New Zealand, colossal birds of a type distinct from any known in other parts of the world. In 1846 and 1847, my eldest son, Mr. Walter Mantell, who has resided in New Zealand several years, made an extensive and highly interesting collection of these fossil remains, which arrived in England in 1848. This series contains skulls, with the mandibles or beaks, bones of other parts of the skeleton, and portions of the egg-shells, of several extinct species and genera of birds; presenting remarkable deviations from the previously known types to which they are most nearly allied.

This valuable accession to our knowledge of the osteology of this extinct race of Ostrich-like birds—some individuals of which must have attained a height of from ten to twelve feet—has yielded important results as to the form, structure, and economy, of these colossal bipeds, and the prevailing characters of the terrestrial fauna of New Zealand in very remote periods. The collection, consisting of above 700 specimens, is now in the British Museum: it was obtained chiefly from a bed of menaccanite or titaniferous iron-sand, that had evidently been washed down by torrents from the volcanic region of Mount Egmont; that snow-capped ridge which forms so striking a feature in the physical geography of the North Island, and is the source of the fresh-water streams that discharge themselves into the ocean along the western shore. The tract of sand from which my son dug up these relics, is on the coast near the embouchure of a small river called Waingongoro, between Wanganui and Waimate. That stream evidently once flowed into the sea far from its present course, for lines of cliffs extend inland from the now dry sand-spit, and bear marks of the erosive action of currents.[91] A few months since, I received from my son another most interesting collection of fossil bones (comprising above 500 specimens), chiefly obtained from the eastern shores of the Middle Island of New Zealand, when engaged as Government Commissioner for the settlement of native claims. These were dug up from a morass of small extent, lying in a little creek or bay at Waikouaiti, some twenty miles north of Otago. This swamp, which is only visible at low water, is composed of vegetable fibres (apparently of the Phormium tenax), sand, and animal matter. The bones are of a deep brown colour, and almost as fresh as if recently taken from a tar-pit. Among the specimens are crania and mandibles, and bones of enormous size. The most remarkable are the entire series of phalangeals, and the two tarso-metatarsals, (26 in number,) of the right and left foot of the same individual bird (Dinornis robustus), which were found standing erect, one a yard in advance of the other; as if the bird had sunk into the mire, and unable to extricate itself, had perished on the spot. These bones were carefully exhumed and numbered seriatim, and are the only instances of the bones of the foot and metatarsus found in natural connexion; they are, consequently, the first certain examples known of the structure of the feet of the colossal birds of New Zealand. The foot of the Moa, to which these bones belonged, must have been 16 inches long, and 18 inches wide; and the height of the bird about ten feet. (See the Frontispiece.)

It would extend this article far beyond the limits assigned to this work, were I to attempt even a cursory account of all the facts and inferences connected with these discoveries. The anatomical and physiological characters of many species and genera will be found in the admirable Memoirs on the Dinornis, Palapteryx, Notornis, &c. by Prof. Owen, in the Transactions of the Zoological Society.[92]

From the facts at present known as to the position of the ossiferous deposits of New Zealand, there is reason to conclude that they bear the same relation to the present state of the country, as the alluvial loam and clay containing the bones of mammoths, Irish Elks, &c. to that of Great Britain. I think we may safely infer that at a period geologically recent, but historically very remote, those islands were densely peopled by tribes of ostrich-like birds of species and genera which have long since become extinct; that many species existed contemporary with the Maories or native human inhabitants, and that the last of the family were exterminated, like the Irish Elk, and the Dodo, by man. If, as the natives affirm, some of the race still exist in the unfrequented parts of the country, they are probably diminutive species, like the Apteryx or Kivi-Kivi, which is the only living representative known to naturalists, of this once numerous tribe of colossal Struthionidæ. The only fossil osseous remains from New Zealand not referable to birds are bones of two species of Seals, and one femur and a few other bones of a Dog. Associated with the relics of the Dinornis and other extinct genera, and unquestionably coeval with them, are crania, mandibles, and other bones, of the living species of Apteryx, Albatross, Penguin, Notornis, Nestor, Water-hen, &c.

The fragments of egg-shells of Dinornis, from Rangatapu, belong to three distinct types, each of very large size; my son, to convey an idea of the magnitude of one egg, of which he dug up a large portion, says, "a gentleman's hat would make a capital egg-cup for it." The markings on the surface of the shells bear a greater resemblance to those on the eggs of the Rhea and Cassowary than of the Ostrich.

A remarkable fact mentioned by my son throws some light as to the comparatively recent extirpation of the Moa. In one spot the natives pointed out some little mounds covered with herbage, as consisting of heaps of ashes and bones, the refuse of the fires and feasts left by their remote ancestors. Upon digging into them, a quantity of burnt bones was discovered: these belonged to Man, Moa, and Dog, and were promiscuously intermingled. These calcined bones present no traces whatever either of the earthy powder or manaccanite sand which the cells and pores of the fossil bones invariably contain. If, as the natives affirm, these are the rejectamenta of the feasts of the aborigines, the practice of cannibalism by the New Zealanders must have been of very ancient date, and could not have originated, as Professor Owen supposed, from the want of animal food in consequence of the extirpation of the colossal birds. (See ante, p. xi.)

IV. Botanical arrangement of Fossil Vegetables.—Mr. Artis, in the Introduction of his work, offers some judicious observations as to the proper method in which the study of Fossil Botany should be pursued. He remarks, "that from the imperfect state in which fossil vegetables are generally found, the ordinary characters by which recent plants are referred to their congeners, can scarcely ever be detected in them. The sexual organs on which the systems of Linnæus and Jussieu are founded, and even the integuments of those organs while in the state of flowering, have uniformly perished. The external parts of the seed or fruit exist, indeed, in a fossil state, but they are almost always insulated from the other organs. If leaves are found, it is almost certain that scarcely any portion of the stem will be attached to them; if the external parts of a trunk, then very rarely any vestiges of the branches and foliage. And when traces of the internal structure can be discovered, it is seldom that the external character of the stem remains.

"In consequence of this deficiency of the essential characters on which the determinations of the botanist are founded, there exists a necessity for examining more minutely and accurately than has yet been done, the internal structure of recent plants; their habits of growth, the cicatrices or scars left on the stem by the leaves that are spontaneously shed, the different appearances which their fruits exhibit in their various stages of development—all these points must be minutely studied before we can obtain any certainty as to the identity of fossil and living species of plants.

"It is not by publishing detached and unconnected delineations and descriptions of fossil plants, as they occasionally occur, that the knowledge of them can be considerably promoted. A systematic arrangement must be formed; and the first step to this is the accurate determination of the species. Hoc opus, hic labor est."

"It will be seen," he observes, "in the course of this work, how easy it would be to imagine parts of the same specimen to be different species, when they happen to be broken and dispersed. I can confidently assert, that in at least a thousand different specimens which I have had in my possession, not more than a hundred distinct species can be recognised. Furthermore, still fewer indeed can be referred to any living species; for it is not the fern-like leaf of a plant, the palm-like cicatrix, or the cane-like joint of a stem, that will suffice to identify them with those tribes of the vegetable kingdom. The whole anatomy of the plant must be studied. The subject has, indeed, been begun by Professor Martins, in his comparison of certain fossil stems of plants with those of the living plants growing in the Brazils, but the study is as yet too new to afford certain results. Accordingly, several of that professor's opinions are at variance with those of M. Adolphe Brongniart, who has also compared the recent and fossil vegetables together on this plan. But by following up the comparison, which has been so successfully adopted by Baron Cuvier, in the study of fossil animals,[93] similar results may be expected, and a knowledge of the extinct plants be at length attained."

Mr. Artis then gives an abstract of the systems of Baron Schlotheim, Count Sternberg, Professor Martins, and M. Adolphe Brongniart, which I am Induced to subjoin as a useful record of the state of fossil botany twelve years ago:—

"The Baron Schlotheim, who published in 1804 the first part of a Flora der Vorwelt, followed up his researches of this kind by a catalogue of his cabinet, under the title of 'Die Petrefactenkunde auf ihrem jetzigen Standpunkte erläutert,' published in 1820, to which two Appendices have since been added in 1822 and 1823.

"The arrangement made by the Baron, so far as regards the vegetable part of his cabinet, is as follows. His specimens are first divided into five Sections, or Orders:—

1. Dendrolithes, containing the remains of trees, which are subdivided into three sub-sections.

A. Lithoxylites, of which no characters are given, but from the specimens mentioned by him, he evidently arranges in this place the wood-stone and wood-opal of the mineralogists.

B. Lithanthracites, in which are placed the bituminized stems, and other parts of trees.

C. Bibliolithes.—Fossil leaves, mostly of the later formations.

2. Botanolithes.—Comprising those kinds of fossil plants which cannot be considered either as trees or shrubs, nor as belonging to the plants of the old coal formation.

All the specimens belonging to the preceding sections are merely enumerated, and not distinguished by generic and trivial names, as is the case with the following.

Phytotypolithes.—Fossil plants of the stone-coal formation. These are divided systematically into genera and species. The genera are as follow:—

a. Palmacites, containing fifteen species.
b. Casuarinites, " five.
c. Calamites, " ten.
d. Filicites, " twenty-three.
e. Lycopodiolithes, " five.
f. Poacites, " four.

In the whole sixty-two species.

4. Carpolithes.—Of which he enumerates fifteen species as present in his collection. This division is considered as a genus, as is also the next.

5. Anthotypolithes.—The cabinet contains only one species, namely the Anthotypolithes ranunculiformis."

In 1820, Gaspard Count Sternberg published in German, the first number of a work which has been translated by the Comte de Bray, under the title of "Essai d'un Exposé Geognostico-Botanique de la Flore du Monde Primitif." Of this translation a second and third part appeared in 1823 and 1824. In these successive numbers the Count has communicated the state of his knowledge as it grew up under his hands, in consequence of his own labours and those of his friend, Baron Schlotheim. The genera, as they are successively developed in the work, are the following:—

This genus is subdivided in the first number into two sub-genera, but this division is not noticed in the additional species quoted in the succeeding numbers.

Lepidotæ.—Scales convex.

Alveolariæ.—Scales sub-concave.

In the second number the following genera are given:—

The third number contains the following additional genera:—

The genera thus successively established, may be arranged in the following order:—

In November 1821, Professor Martins read to the Botanical Society of Ratisbon, a paper which was afterwards published in its Memoirs for 1822. This paper was entitled, "De Plantis nonnullis Antediluvianis ope specierum inter tropicos viventium illustrandis;" in it several of the species mentioned by Baron Schlotheim and Count Sternberg are referred to the orders and genera of recent plants; and the following genera are proposed:—

M. Adolphe Brongniart has given the following classification of fossil plants, in his Essay "Sur la Classification et la Distribution de Végétaux Fossiles" inserted in the "Mémoires du Muséum d'Histoire Naturelle;" and also printed separately in quarto, Paris, 1822:—

STEMS.

Class I.—Stems whose internal organization is recognisable.

Class II.—Stems whose internal organization is no longer distinct, but which are characterised by their external form.

FOLIAGE.

This genus is subdivided into four sections, as follow:—

Class III.—11. Filicites.—Frond disposed on a flat surface, symmetrical; secondary rib simple, forked, or rarely anastomosing.

These are divided Into five sub-genera:—

Class IV. Organs of fructification.

Order I. Carpolithes.—Fruits or seeds.

Order II. Antholithes.—Flowers.[103]

The numerous additions and modifications, which subsequent experience and discoveries have led M. Brongniart to introduce into his classification, will be found in an article recently published (1849) in the "Dictionnaire Universel d'Histoire Naturelle," under the title of "Tableau des Genres de Végétaux Fossiles, considérés sous le point de vue de leur classification botanique et de leur distribution géologique."

V. Fossil Cephalopoda, Nautilus, Ammonite, &c.—The fossil remains of the molluscous animals, named Cephalopoda, from their organs of prehension being arranged around the head or upper part of the body, are the most ancient, numerous, and interesting, of this class of animated nature in the mineral kingdom. These relics are among the most varied and striking of the extinct beings that occur in the sedimentary strata, from the most ancient secondary formations, to the most recent tertiary. The living species are but a feeble representation of the countless myriads which must have swarmed in the ancient seas.

The animal of the Cephalopods is composed of a body, which is either enclosed in a shell, as in the Nautilus, or contains a calcareous osselet or support, as in the Sepia or Cuttle-fish; it has a distinct head, and eyes as perfect as in the vertebrated animals, with complicated organs of hearing, and a powerful masticating apparatus, surrounded by arms or tentacula. Below the head there is a tube which acts as a locomotive instrument, to propel the animal backwards, by the forcible ejection of the water that has served the purpose of respiration, and which can be ejected with considerable force by the contraction of the body.

Their fossil remains consist of the external shell and the internal osselet; and in the naked tribes, of the soft parts of the body, the ink-bag, &c., as noticed in the account of the Belemnite and Belemnoteuthis.

The shell varies exceedingly in the different genera. In the group characterised by smooth septa, and a medial or submedial siphuncle, as the Nautilus, the earliest or most ancient type is straight, as in the Orthoceras (Plate LVIII. fig. 14) of the palæozoic formations; the intermediate forms present various modifications of the spiral, and terminate in the completely discoidal shell of the living genus; while the other group, that with sinuous or foliated septa and a dorsal siphuncle, commences in a discoidal type—the Ammonite, which gradually passes through the various modifications of Crioceras, Scaphites (Plate LXI. fig. 10), Hamites (Plate LXI. fig. 3), Turrilites (Plate LXI. fig. 12), &c.; and finally becomes extinct in the straight Baculites (Plate LX. fig. 2).

In argillaceous strata, as the Kimmeridge and Oxford clay, London clay, &c., the shells of Cephalopoda are oftentimes beautifully preserved; the chambers are frequently filled with the solid matrix, but in many instances these cavities are lined either with brilliant pyrites or spar. Stony or sparry casts of the cells or chambers, the shell having perished, are another common state in which vestiges of these animals occur. Sometimes the cast of each chamber is isolated, so as to present a series from the innermost to the outermost cell. Sections of those casts, in which the chambers are filled up with spar, constitute specimens of great beauty and interest. The so-called snake-stones are, of course, mere casts of Ammonites;[104] those of Whitby, from the lias limestone, are well known to every collector; the casts of a very large species are common in the oolite, especially at Swindon, in Wiltshire, and in the neighbourhood of Bath.

VI. The Carboniferous Deposits, or Coal Measures.—The various deposits of Coal have manifestly been formed under different local circumstances. Some have been peat-bogs, to which repeated additions have been made by successive subsidences of the land; others have been deposited at the bottom of lakes and rivers, and these are associated with remains of fresh-water shells and Crustacea; others have accumulated in the abyss of the ocean, having been formed by the drifting and engulfing of immense rafts of trees and other vegetable matter, like those of the Mississippi; others in inland seas, the successive layers of vegetables having been supplied by periodical land-floods. There can be no doubt that coal has been, and may be, produced under all these conditions; and at different periods, and in various localities, all these causes may have been in operation. But the great series of ancient coal-formations present a remarkable uniformity of character, not only throughout Europe, but also in America and other parts of the world. A coal-field (as a group of strata of this kind is commonly termed), is generally composed of a series of layers of coal, clay, shale, and sand, of variable thicknesses, based on grit or limestone, abounding in marine shells and corals; and the most remarkable phenomenon is the constant presence beneath every bed of coal, of a thick stratum of earthy clay, and of a layer of shale or slaty clay above it. One of the series of triple deposits of which a coal-field consists, presents therefore the following characters:—

1. Under-clay; the lowermost stratum. This is a tough argillaceous earth or clay, which on drying becomes of a grey colour, and very friable; it is occasionally black, from an intermixture of carbonaceous matter. This bed almost invariably contains an abundance of Stigmariæ (see Plates XXII. XXIII.), of considerable length, with their rootlets attached, and which extend in every direction through the clay (as shown in the figures 1, 2, 6, pp. 199, 201). These roots commonly lie parallel with the planes of the stratum, and nearer to the top than to the bottom.

2. Coal.—A carbonized mass, in which the external forms of the plants and trees composing it are obliterated, but the internal structure, in many instances, remains. Large trunks, and stems, and leaves, are rarely found in it.

3. The Roof, or upper bed.—This consists of slaty clay, abounding in leaves, trunks and branches, fruit, &c.; it includes layers and nodules of ironstone, inclosing leaves, insects, Crustacea, &c. In some localities beds of fresh-water shells, in others of marine shells, are intercalated with the shale; finely laminated clay, micaceous sand, grit, and pebbles of limestone, sandstone, &c. are also often interstratified. The principal illustrative specimens of the leaves, fruit, &c. (as those in Plate XXX. to Plate XXXIV.) are found in this bed.

Thus an uninterrupted series of strata, in which triple deposits of this kind are repeated, (often thirty or forty times, and through a thickness of several thousand feet,) constitutes the predominant character of the ancient coal formations wherever they have been explored. The difficulties attending a satisfactory solution of this problem, are fully stated in the last edition of my Wonders of Geology (Vol. ii. Lecture vii.), and to that work I must refer the reader for a more extended consideration of this highly interesting subject.