impressions, (impressa, Linnéus; typolithi, Walher); casts, (redintegrata, Linnéus); and incrustations, (incrustata, Linnéus.)

Fossils naturally divide into vegetable and animal, according to which of those kingdoms they originally belonged: those of the vegetable kingdom shall be the first subjects of our inquiry.

The parts of vegetables confined in subterranean situations suffer, according to circumstances, either a complete resolution of composition, the lighter parts becoming volatilized, whilst the more fixed remain and form the substance which is termed mould (humus); or, as is supposed by Mr. Parkinson, it passes through another process, which he considers as fermentative, and becomes bituminous. Wood, thus changed, is called lignum fossile bituminosum, surturbrand, and Bovey coal. By the extension of this process, the same author supposes, that the substances termed bitumens, (naphtha, petroleum, and asphaltum), are formed. To the same process he also attributes the formation of amber, of which however no proof appears. That jet, cannel coal, and the common coal employed in domestic uses, have had a vegetable origin is rendered highly probable, from the frequency with which they manifest the impressions of various vegetable bodies.

Thus, perhaps, the formation of the bituminous fossils may be satisfactorily explained; but by far the greater number of vegetable fossils are of a lapideous nature, and necessarily owe their formation to very different processes; which the same author supposes are, in general, preceded by the process by which bitumen is formed. Many bodies which are evidently of vegetable origin may be now found existing in a lapideous state, either calcareous or silicious; and many others are found possessing certain marks of the presence of some metallic substance.

To explain these formations various opinions have been formed. Some have supposed the injection of the impregnating matter, in a state of fluidity, by ignition; whilst others have imagined the gradual abstraction of the original particles of the body, and the regular deposition of the impregnating particles in the spaces which have just been left by the original matter. Mr. Parkinson, who does not admit of this substitution, attributes the formation of this description of fossils to the impregnation of vegetable substances, which have undergone different degrees of bitumization with water, holding the earths or the metals in solution. Thus with lime is formed the calcareous wood or wood-marble of Oxfordshire and Dorsetshire, of Piedmont and of Bohemia; with silex is formed the calcedonified, agatified, and jasperified wood (holzstein); and with the addition of alumine, &c. the fossil woods which now partake of the nature of pitch-stone, and wax-opal (holzopal). In other situations metallic impregnations occur; as in such woods as are impregnat ed with the pyrites of iron, so frequently found in our islands; and the beautiful woods of Siberia, containing the hydrat and carbonat of copper.

Various parts of trees and plants (phytolithi) are found in a mineralized state. Not only fossil wood (lithoxylon), as has been just noticed, but the leaves (lithophylla or lithobiblia), and fruits (carpolithi) of different trees or plants are thus found. Of the woods, several, from their form and texture, have been supposed to have been originally oak, willow, and such trees as now exist

in a recent state; whilst others differ, in both these respects, from any species of wood which is now known.

The impressions of the stalks and leaves of plants are very frequently found in many parts of the world, in lofty mountains, as well as at a considerable depth below the surface; and not only the impressions, but the substance itself of different vegetables are also thus found; but in no situation more frequent than in the neighbourhood of coal mines.

In general these vegetable remains are found deposited in laminæ, in the schistose strata which accompany the coal; but the most perfect remains are commonly found in roundish nodular masses of ferruginous clay, which abound in the strata accompanying the coal. These are commonly termed catsheads by the workers of the coal mines, and contain pieces of fern, &c. very few, indeed, of which are found to agree with any known recent plants. The vegetable remains in these fossils appear to confirm the opinion above mentioned, of the bituminization of fossil vegetables; since these leaves are completely changed into a bituminous substance.

The remains of fruits are, perhaps, no where found so abundantly as in the Isle of Sheppey, where they are dug up in great variety; very few, however, being found which agree with any known recent fruits. Where any resemblance appears, it is with fruits which only grow in the warm Asiatic regions.

Fossil roots of plants of trees are very rarely found; a circumstance not very easily explained; since they possess (especially the roots of trees) that degree of solidity which appears to be favourable to the process of petrifaction. From the want of this necessary property it undoubtedly is that we possess so few remains of tender flower leaves, and none of pulpy fruits.

From the same cause, the great proneness to decomposition, the number of animal fossils is considerably limited: those substances being only preserved in a mineralized state, which originally possessed a considerable degree of solidity; such are the bones, teeth, horns, shells, scales, &c. The animal, however, far exceeds the vegetable king dom in the number and variety of fossils which it yields, as well as in the distinctness of form, and excellency of preservation, in which they are found.

Adopting in a great measure the arrangement of Waller, we shall commence our examination of the animal fossils with those which have derived their origin from corals. These fossils are, of course, merely the remains of the dwellings which have been formed by the various coral insects, and which are so frequently found in the cabinets of the curious.

Immediately on commencing this examination, we are struck with a similar want of agreement between the recent and fossil corals, with that which has been noticed between recent and fossil vegetables. Of the genus tubipora it does not appear, at least by the observations made in Mr. Parkinson's second volume of The Organic Remains of a former World, that a single species which is known recent has been found as a fossil. Several fossil species are, however, described, of which nothing similar is known in a recent state. The most striking of these is the tubipora catenularia, or chain coral, the surface of which, in consequence of the tubes being in contact at their sides, has frequently a very curious reticulated or

catenulated appearance. Tubipora fascicularis, T. stellata, T. repens, and T. strues, which have been described by different authors, and which are unlike to any known recent tubipore, give reason for supposing that the number of species of fossil tabipores exceeds that of the recent species.

The fossil madrepores are not less rich in variety, nor less comparatively numerous, than the fossils of the preceding genus. The forms of several species of the fossil madrepores do frequently approach to those of the different recent species; but in a considerable number of the fossil madre pores no resemblance is discoverable, except in their stelliform openings, with any recent coral. So great indeed is this departure in some instances from the general characters of our, present known madrepores, that it has been deemed difficult to determine, whether some fossil specimens should be considered as madrepores or as alcyonies. It is impossible, without the aid of numerous figures, to give satisfactory notions of the forms of the several fossil madrepores which have been hitherto discovered; the most interesting only will therefore be here particularized.

The madrepores consisting of a single star appear to be much more numerous in a mineral than in a recent state. These are either of a discoidal form, having a concave superior and a convex inferior surface; of a pyramidal top-like form, terminating in a pedicle; or of a lengthened pyramidal form, bearing in some, from a slight curvature, the appearance of the horn of an animal; whilst others are cylindrical for a considerable part of their length.

The first of these, madrepora porpita, the shirtbutton madrepore, has been long known to the collectors of fossils in this kingdom. Dr. Woodward describes several of them, as mycetita discoides. The second species (madrepora turbinata) is also frequently found in different parts of Great Britain, as well as in Sweden, Norway, and in several parts of France, Switzerland, and Italy. These latter fossils have been termed by Dr. Woodward mycetita conoides seu calyciformes. When they have acquired somewhat of a hornlike shape, they have been distinguished by the term ceratites; and when they have possessed more of the cylindrical form, they have been termed columelli lapidei et hippurite; and from a supposed resemblance, they have been also considered as the petrified roots of briony. Some of the single starred corals are found united at their pedicle, and approaching towards each other at their summits, though disjoined nearly through their whole length. These, from their resemblance to petrified reeds, have been named junci lapidei.

It would be useless to attempt, in this sketch, to specify the considerable variety of fossil madrepores formed of aggregated circular stars, and which have been designated as astroites, &c. Those which are composed of angulated stars are, perhaps, not so numerous: many of these, however, are very different in their appearance from those which are known in a recent state. The one most known in these islands is the lithostrotion, sive basaltes striatus et stellatus, of Llwyd. The exact union of the sides of the polygons giving a tolerably correct idea of minute basaltes. The compound madrepores, the stelliform part of which are extended in undulating labyrinthean forms, appear to be much less numerous as fossils than any of the other corals: their existence in a silicious state very rarely occurs.

The millepores do not appear to be nearly so frequently found in a mineral as in a recent state. Several fossils have been placed among the mille. pores which undoubtedly should rank with the madrepores: such are the millepora simplex turbinata, and the millepora simplex discoides, of Waller and Gesner; a careful examination shewing, that these differ from the porpital and turbinated madrepores, only in their being formed of numerous tubes, possessing an internal stellated structure.

Of the genus isis one species only appears to be known as a fossil. This species was earliest described by Scilla, who at first conjectured it to be the leg-bone of some animal. Specimens are frequently found in the Calabrian mountains, and have lately been also found in some parts of Wiltshire. Of the genera cellepora, antipathes, and Gorgonia, fossil specimens appear to be rather uncommon.

The corallo-fungite of Waller are evidently the fossil remains of the alcyony. These have been long described by Volkmann, Scheuchzer, and others, as fossil fruits, and have obtained, from their re semblance to figs, &c. the appellations of ficoides, caricoides, &c.; whilst others of a different form have been named lycoperditæ, fungitæ pilcati, &c. A fossil alcyony has even been described by Volkmann and Scheuchzer as a fossil nutmeg.

The encrini and pentacrini have been always, and very properly, considered as the most curious of the fossil zoophytes. The encrinus (Plate LXXX. Nat. Hist.) possesses the distinguishing character of having its spine, or, as it has been generally called, its tail, composed of cylindrical or orbicular vertebræ, pierced through their centre, and marked with diverging striæ on their articulating surfaces. On the superior termination of these is placed the base of the body of the animal, formed of five trapezoidal bodies, termed by Rosinus articuli trapezoides, which inclose five small bodies, which form the center of the base; the whole of these forming that which Rosinus denominated the pentagonal base. From each of these proceed six other bodies, on the two last of each series of which are placed the arms of the animal, which divide into fingers; from the internal surface of these proceed almost innumerable articulated tentacula. This fossil has long possessed the name of the encrinus, or stone lily: its resemblance to that flower having led to the suspicion that it was a petrifaction of a Bower, approximating in its form to the lily: its animal origin is however now completely ascertained. Indeed, if a doubt had remained, it would have been removed by the circumstance of the animal membrane, or cartilage, having been actually discovered in the fossil. (Organic Remains of a former World, vol. ii. p. 166.) Several other species of this animal are also described in the work just referred to; but hitherto no recent animal bas been found which can be referred to this genus.

The fossil pentacrinus differs from the encrinus, in its vertebræ being of a pentagonal form, and in its arms, fingers, and tentacula being capable of being much more widely spread and extended than are those of the encrinus. It appears from Mr. Parkinson's account, that there are several species of this fossil, the existence of some recent species of which have been also ascertained.

The encrinital vertebræ have been hitherto termed trochite when separate, and entrochi when connected in a series. The single vertebræ of the pentacrinus have been distinguished as asteria,

Of the asteriæ, or stellæ marinæ, some very few specimens have been found fossil; but they occur very rarely, and have, in general, been found in a condition too imperfect to allow of any positive opinion being formed, respecting the species to which they belong.

The fossil echini are very numerous, upwards of forty species, known only as fossils, being enumerated by the illustrious Linnéus; to delineate, therefore, even those most deserving of notice could not be here well accomplished, a circumstance, however, which is not so much to be regretted, since, through materially different, they approach very nearly in their general form to the recent species. Those which possess a hemispherical, or a nearly orbicular form, with large mamilla-like protuberances, and the anus disposed vertically, have been distinguished as the turban echini (echini cidares); those which resemble a shield or buckler in their figure are termed the shield echin (clypei, Kleinii), and one of the largest of these has been named the polar stone by Dr. Plot. (Plot's Oxfordshire, p. 91.) When of a depressed circular form, with the anus in the edge of the inferior part, they are the fibula of Klein; of a conical form, the eaglestone of the Germans (conuli, Kleinii); with a circular base, the quoit echinus (discoidei, Kleinii). When the base is an acute oral, the mouth and anus being at the opposite ends, they are termed the belinet echinis, (cassides et galer, Kleinii); and when heart-shaped, with a sulcated superior surface, they are called suake's hearts (spatangi, Kleinii).

The attempt to particularize the various species of fossil shells which have been found would require a large volume: all that can be here done is to notice some of those which totally differ from any which exist in a recent state, and to offer some few remarks on those which approximate, or are perhaps similar to some of the species which are known in a recent state.

With respect to the state in which fossil shells are found, it is necessary to remark, that in some situations, shells which have been buried for ages, by the natural changes which the surface of the earth has undergone, are found very little changed, except from the loss of colour, and having been rendered extremely fragile; that in other situations the substance of the shell has been so injured, as to be reduced to very small fragments, and even to a fine powder, leaving in some instances a stony, correctly moulded, cast of the cavity of the shell; that very frequently the substance of the shell is entirely altered, having become a calcareous stone, or a silicious or pyritous mass, and that the shells of a former world are frequently found in masses of marble, which is called lumachelli, or shelly marble.

Of the multivalves, the chitou does not appear to have been found in a mineralized state; and although several species of lepas have been found in a mineral state, they are by no means frequent fossils. Lepas anserifera is said to have been found fossil, as well as lepas diadema; these must, however, be exceedingly rare fossils.

Fossil shells of the phloas are by no means common; the phloas crispata has been, however, found among the Harwich fossils.

Fossil bivalves are very common fossils; they are, as might be expected, very seldom found in pairs, except when united by a lapideous mass, which prevents the examination of their hinge, or

are objects highly worthy of examination.

The mya pictorum is described by Solander as existing among our Hampshire fossils: a fossil mya of three or four inches in length is found also in the rocks near Bognor. Remains of the Solen siliqua; and of the Solen ensis, have been found at Harwich, and a small fossil shell, named by Solander Solen ficus, has been found between Lymington and Christchurch.

Fossil shells of the genus tellina, as well as of cardium, mactra, donax, venus, spondylus, chama, arca, and particularly ostrea, have been found of many species. But no bivalve exists as a fossil in such prodigious numbers, and in such various species, as those of the genus anomia. These shells are characterized by the beak of the largest or under valve, which is perforated, being greatly produced, rising or curving over the beak of the smaller or upper valve. Anomia lacunosa is one of the most abundant of these species. They are found in considerable quantities in different parts of England, particularly in Lincolnshire, Warwickshire, and Gloucestershire. Anomia terebratula, is another fossil of this genus, which exists in different counties in this island, in great abundance.

Of the genus mytilus several species are known as fossils, some of which approach very near to those which are known recent: one in particular appears to differ very little indeed from mytilus modiolus. Fossil shells of the genus pinna, in any tolerable state of preservation, are not frequently found: the shells are in general so fragile as to render it very difficult to obtain them tolerably perfect; or so that but little information can be yielded respecting the species to which they belong.

No fossil shell appears yet to have been found which can with certainty be placed under the genus argonauta. But of the genus nautilus, specimens are very frequent. These have been found in several parts of this island: some very fine specimens have been found at Lime in Dorsetshire, in different parts of Wiltshire, and at Whitby in Yorkshire. The finest specimens are perhaps found in the neighbourhood of Bath, and in the isle of Sheppey in Kent, at which latter place they are found exceedingly large, and still retaining a resplendent pearly shell.

The cornu ammonis, which, if we except the extremely minute shells of this kind which have been seen by Plancus, and others, in the sea sand on the Venetian shores, may be said to be only known to us in a fossil state.

Like the nautilus, the cornu ammonis is divided into compartments, by regularly disposed partitions, and these partitions are perforated, as are those of the nautilus, although it is by no means easy to point this out, except in very few speci

mens.

There are none of the fossil shells, except per haps the anomiæ, which can vie in the variety of their species with the cornu ammonis. The sbell of some is perfectly smooth over its whole surface; in others smooth at the sides, but ridged or beset with spines at the back; and others, though smooth at the side, are crenulated at the back. The species most commonly met with have the shell variously ridged; some with small close striæ, and others with large and round ridges. In some the ridges are single, in others bifurcated, and in others trifurcated. In some, and these are least common, the shell is tuberculated: these tuberculæ differing considerably in different