Chapter VI: Fossil Vegetables (1)

In the present section of this work, I propose to explain the botanical arrangement and nomenclature of fossil plants; and figure and describe one or more species of the genera that are most likely to come under the observation of the student, either in public or private collections, or in the course of his researches in the field.

To determine the botanical relations of fossil leaves and stems, reference must be had to works expressly devoted to the subject; namely, the "_British Fossil Flora_," by Dr. Lindley and Mr. Hutton, and the "_Histoire des Végétaux Fossiles_," by M. Adolphe Brongniart. The classification of the last-named eminent botanist is here adopted, as the most easy of application.

With regard to the nomenclature, it may be necessary to remark, that when a fossil plant undoubtedly belongs to a recent genus, the usual botanical name is employed: for example, _Equisetum Lyellii_; when the fossil does not possess all the generic characters, yet is evidently allied to a recent genus, the term _ites_ (from λιθος, _lithos_, stone), is added--as _Equisetites_, _Palmacites_, &c.; and this termination is invariably adopted by some authors. When the fossil plant differs altogether from any known type, it is distinguished by some arbitrary generic name, as _Bucklandia_, _Sigillaria_, &c.

There are also a few provisional genera for the reception of fossil leaves, fruits, and stems, whose characters and relations are but imperfectly known; as Carpolithes, Endogenites, &c. Upon these principles the present arrangement has been founded: the progress of discovery will, of course, be continually adding to the list, and the classification require to be modified.

[Sidenote: FOSSIL CRYPTOGAMIA.]

The following account of the principal types of the ancient floras whose relics are preserved in the mineral kingdom, though commencing with those of the most simple structure, the _Cryptogamia_, and advancing to the higher orders, is not strictly botanical; for it was found convenient, in some instances, to notice certain species and genera of different orders under the same head, from their occurrence in the same geological formations.

It is estimated that not more than two thousand species of plants have been discovered in a fossil state, while the known recent species amount to upwards of eighty thousand.

Cellular Cryptogamia; Algæ.--The plants designated by botanists _Algæ_, and commonly known as sea-weeds, lavers, and fresh-water mosses, are of the most simple structure--mere aggregations of cells--but present innumerable varieties of form and magnitude: many species are mere vesicles of such minuteness as to be invisible to the unassisted eye, except accumulated in countless myriads, when they appear as a green, purple, or reddish, slime in the water; or as a film on wood or stone, or on the ground, in damp situations; while others are tough branched marine plants, many fathoms in length.

The Algæ form three principal groups: 1. the _jointless_, as the Fuci, the Dulses, Tangles, and Lavers: 2. the _jointed_, which are composed of thread-like articulated tubes; such are the fresh-water Confervæ: 3. the _disjointed_, or Brittle-worts, so called from their spontaneous self-division, which is in some kinds complete, in others only partial; and these, by separating transversely, and leaving each cell or frustule attached at the angles, produce those beautiful chains of angular green transparent cases, so constantly seen under the microscope when substances from fresh-water streams or lakes are submitted to examination.

As many of these forms are endowed with spontaneous motion, and possess other properties common to animal organization, it is not surprising that their vegetable nature was doubted, and that even so profound a naturalist as M. Ehrenberg placed them in the animal kingdom: the greater number being comprised in his family of _Bacillariæ_, were described in the former edition of this work, as Infusoria or Animalcules; in conformity with the classification of the illustrious microscopist, whose splendid works and indefatigable labours have so greatly promoted the advancement of microscopical investigation.[61]

[61] The whole of the objects called _Infusoria_ in the first edition of "The Medals of Creation" belong to various kinds of Diatomaceæ.

[Sidenote: FOSSIL DIATOMACEÆ.]

These minute vegetable organisms are placed by botanists in two tribes, the _Diatomaceæ_ or the _Brittle-worts_, and the _Desmidieæ_. The latter are exclusively inhabitants of fresh-water, while a large proportion of the former are marine plants. Some naturalists (M. Brébisson) restrict the name _Diatomaceæ_ to those species which secrete siliceous envelopes; and that of _Desmidieæ_ to those whose structures are not siliceous, and are reducible by heat to carbon. As the durable parts of these plants alone concern the geologist, the name _Diatomaceæ_ will be employed as a general term in reference to their fossil remains.

These tribes of Algæ abound in every lake and stream of fresh-water, in every pool or bay, and throughout the ocean from the equator to the poles. Certain kinds of sea-weeds secrete carbonate of lime; but the Diatomaceæ have the power of separating silex, or the earth of flint, from the water, by some unknown process, and their tissues are composed of pure quartz: hence, under the microscope, their remains, consisting wholly of rock crystal, exhibit the most exquisite forms, elaborately fretted and ornamented (see _Lign. 4_). After the death and decomposition of these plants, their durable frustules or cases appear as colourless discs, cups, spheres, shields, &c., and these accumulate at the bottom of the water in such inconceivable numbers, as to form strata of great thickness and extent. Slowly, imperceptibly, and incessantly, are the vital energies of these atoms separating from the element in which they live the most refractory and enduring of mineral substances, silex, and elaborating it into imperishable structures, and thus adding enormous contributions to the accumulations of detritus, which make up the sedimentary rocks of the crust of the globe.

The extent of this infinitesimal flora throughout regions where no other forms of vegetation are known, is strikingly demonstrated by the observations of our eminent botanical traveller. Dr. Joseph Hooker, in his account of the Antarctic regions.[62]

[62] "On the Botany of the South Polar Regions;" in Sir J. Ross's Voyage of Discovery.

"Everywhere," Dr. Hooker states, "the waters and the ice alike abound in these microscopic vegetables. Though too small to be visible to the unassisted eye, their aggregated masses stained the iceberg and pack-ice wherever the latter were washed by the sea, and imparted a pale ochreous colour to the ice. From the south of the belt of ice which encircles the globe, to the highest latitudes reached by man, this vegetation is everywhere conspicuous, from the contrast between its colour and that of the white snow and ice in which it is imbedded.

"In the 80° of south latitude all the surface ice carried along by currents, and the sides of every berg, and the base of the great Victoria barrier itself--a perpendicular wall of ice, from one to two hundred feet above the sea level--were tinged brown from this cause, as if the waters were charged with oxide of iron. The majority of these plants consist of simple vegetable cells enclosed in indestructible silex; and it is obvious that the death of such multitudes must form sedimentary deposits of immense extent.

"The universal existence of such an invisible vegetation as that of the Antarctic Ocean is a truly wonderful fact, and the more so from its being unaccompanied by plants of a high order. This ocean swarms with mollusca, and entomostracous crustaceans, small whales, and porpoises; and the sea with penguins and seals, and the air with birds; the animal kingdom is everywhere present, the larger creatures preying on the smaller, and these again on those more minute; all living nature seems to be carnivorous. This microscopic vegetation is the sole nutrition of the herbivorous animals; and it may likewise serve to purify the atmosphere, and thus execute in the Antarctic latitudes the office of the trees and grasses of the temperate regions, and the broad foliage of the palms of the tropics."

Dr. Hooker also remarks that the siliceous envelopes of the same kinds of diatomaceæ now living in the waters of the South Polar Ocean, have contributed in past ages to the formation of European strata; for the tripoli and the phonolite stones of the Rhine, contain the siliceous envelopes of identical species.

Such are the comments of one of our most distinguished botanists, on the phenomena under review. The reader will perhaps ask, what then are the essential characters which separate the animal from the vegetable kingdom? To this question it is impossible to give a satisfactory reply: perhaps the only distinction that will be generally admitted by zoologists and botanists is the following:--_animals require organic substances for their support; vegetables derive their sustenance from inorganic matter_.

[Sidenote: RECENT DIATOMACEÆ.]

Recent Diatomaceæ. _Plate IV._--To familiarize the reader with the nature of these vegetable organisms, a few recent species are represented in Plate IV., coloured as they appear when alive, under the microscope; the figures are magnified as expressed by the fractions.

_Xanthidium._ _Plate IV. figs. 1, 2, 3, 4, 5._--The case or frustule of this genus consists of a hollow, siliceous globe, beset with spines. The increase of the Xanthidia by self-division, produces the double appearance in the figures, all of which are in the progress of separation.[63]

[63] The organisms so abundant in the flint and chalk, and which were referred by M. Ehrenberg to this genus, and consequently described under the name of Xanthidia by myself and others, are certainly in nowise related to the recent forms: they are flexible envelopes, and probably belong to zoophytes; as will be shown in the sequel.

_Pyxidiculum._ _Plate IV. fig. 2._--The case is a little saucer-shaped box, and is invested by a membrane.

_Bacillaria._ _Plate IV. fig. 6._--A simple siliceous frustule, of a prismatic shape, forming a brilliant chain, which often appears in zigzag, in consequence of incomplete self-division. An immense number and variety of forms are placed in this family by Ehrenberg, with a multitude of generic and specific names. The fresh-water species inhabit every pond and lake, and the marine every sea. Fossil species are equally abundant.

_Cocconeis._ _Plate IV. fig. 7._--This is a very elegant type; the frustule consists of a simple siliceous case, with a central opening; it never occurs in chains like the former. It has been found fossil near Cassel.

_Navicula._ _Plate IV. figs. 8, 9, 14, 15._--The plants of this genus are free, and float in the water apparently by the agency of cilia. Their case is a boat-like envelope with six openings, composed of pure silex, and in many species is exquisitely ornamented. Figs. 8 and 9. show a living _Navicula_, viewed in front, and in profile: in _fig. 9_ are represented the currents produced when the body is moving through the water; after Ehrenberg. Fossil _Naviculæ_ abound in many tertiary strata.

_Galionella._ _Plate IV. figs. 10, 11._--These algæ are free, and the frustules of a cylindrical, globular, or discoidal form; they occur in chains, in consequence of the self-division being imperfect, and the new individuals remaining attached to the old. The _Galionellæ_ are most abundant and prolific, and inhabit every pool, stream, and lake: fossil species occur in the Virginian marls, and other strata.

_Synhedra._ _Plate IV. fig. 12._--The frustules are siliceous, and of a slender, elongated form. The plant is attached by the base (_fig. 12 a._) in youth, and afterwards becomes free. It is found fossil in the Mountain-meal of Santa Flora, and many other deposits.

_Podosphenia._ _Plate IV. fig. 13._--The frustule is cruciform, or wedge-shaped, and attached in youth by the small end, but afterwards becomes free. These plants are often arranged in clusters, as in the figure. M. Ehrenberg states that they inhabit the sea, and not fresh-water; but I have found them in streams communicating with the Thames. _Podospheniæ_ abound in the polishing slate of Bilin.

_Eunotia._ _Plate IV. figs. 16, 17._--The frustule is siliceous, and either simple or bivalve; flat below, and convex, and often richly dentated above. An empty case is shown _fig. 16_; and a group of living _Eunotice_ attached to a stem of conferva, _fig. 17_. Several fossil species have been discovered at Santa Flora.

That the general reader, whose attention is for the first time directed to this subject, may be prepared for the enormous deposits of fossil diatomaceæ that are found in some formations, I subjoin the observations of Dr. Bailey on an elegant fragile species, which hangs together in clusters, appearing like spiral chains, and is about 1/20 of a line in diameter; it is named _Meridion vernale_.

"This fresh-water plant is seen in immense quantities in the mountain brooks around West Point, the bottoms of which are literally covered in the first warm days of spring with a ferruginous-coloured mucous matter, about a quarter of an inch thick, that, on examination by the microscope, proves to be filled with millions and millions of these exquisitely beautiful siliceous organisms. Every submerged stone, twig, and spear of grass, is enveloped by them; and the waving plume-like appearance of a filamentous body covered in this manner, is often extremely elegant. Alcohol completely dissolves the endochrome (_soft colouring matter_) of this species, and the frustules are left as colourless as glass, and resist the action of fire."[64]

[64] Trans. Amer. Assoc. Geolog. 1843, p. 152.

The yellow or ochreous scum observable in ponds, ditches, and stagnant pools, is an aggregation of diatomaceæ, whose frustules are feriniginous, and of such extreme minuteness, that a billion of their cases would not be more than a cubic inch in bulk.[65]

[65] Ehrenberg.

Fossil Diatomaceæ.--From this notice of a few recent types, we proceed to the investigation of the fossil remains of this tribe of Algæ.

In peat-bogs and swamps, both of modern and ancient date, masses of a white marly or siliceous paste (_hydrate of silica_), are often observed, and these are found upon microscopical observation to be wholly made up of the frustules of _Naviculæ_, _Bacillariæ_, _Galionellæ_, &c., with an intermixture of the needle-like spicules of fresh-water sponges. Many of the peat-bogs of Ireland contain layers of a white earthy substance, which, when dry, is of the appearance and consistence of friable chalk, and entirely consists of the siliceous cases of various kinds of diatomaceæ.

(_Seen by transmitted light, and highly magnified._)]

[Sidenote: FOSSIL DIATOMACEÆ OF IRELAND.]

Fossil Diatomaceæ from Ireland, _Lign. 4._--Dr. Drummond describes a bed of this kind near the base of the Mourne Mountains, in the County of Down, Ireland. It consists of a very light white substance, resembling in appearance carbonate of magnesia: it has a coarse and somewhat fibrous fracture, and is easily reduced to powder. It is almost entirely siliceous, and is composed of the cases of diatomaceæ of the usual fresh-water species, without any admixture of inorganic matter.[66]

[66] Mag. Nat. Hist. New Series, vol. iii. p. 353, July 1839.

On the banks of the river Bann, in the same county, there is an extensive stratum of a similar earth, and which, from being in much request for polishing plate, is locally known as Lord Roden's plate powder. This earth is wholly made up of the siliceous frustules of many kinds of this tribe of Algæ, and a few grains under the microscope yield a great variety of exquisite forms: figures of several are given in _Lign. 4_, from specimens of this earth, with which I was favoured by the Countess of Caledon. They comprise two or three species of Navicula, Galionella, Coscinodiscus, Gomphonema, Bacillaria, Stauroneis, &c., and spicules or spines of fresh-water sponges.[67]

[67] The names of the usual kinds of Diatomaceous frustules may be learnt by reference to Mr. Andrew Pritchard's abstract (with coloured figures) of Ehrenberg's Infusoria. The splendid work of Mr. Ralfs, on the British Desmidieæ, 1 vol. 4to, with coloured plates, is the best guide for those who wish to study the recent plants.

Beds of siliceous marl--that is, of argillaceous earth combined with a large amount of minute particles of silex, all of which prove to be organisms when examined by a high magnifying power,--have been found in numerous places not only in England, but all over the world, since M. Ehrenberg first directed attention to their nature and origin.

Near Bryansford (Newcastle), Binstwick in Holderness, and in the Fens of Lincolnshire and Cambridgeshire, extensive fresh-water microphytal deposits have been discovered and examined.

From our Antipodes I have received many examples of these vegetable earths. My eldest son, Mr. Walter Mantell, discovered an extensive bed of white marl on the banks of the great brackish-water lake of Waihora, in the middle island of New Zealand, consisting entirely of frustules of Bacillariæ. From New Plymouth he obtained some new and exquisite forms of Navicula, Stauroneis, &c.; ranges of low hillocks of sand, of considerable extent, being made up of microphytes (_microscopic plants_).[68]

[68] See a Memoir on the Geology and Fossil Remains of New Zealand, from the researches of Walter Mantell, Esq.--_Geol. Journal_, vol. vi. _pl._ 29.

Mr. Dean, of Clapham Common, informs me that a large quantity of white earth sent from New Zealand as native magnesia, he found to consist wholly of frustules of diatomaceæ, chiefly of _Galionellæ_. (See _Lign. 5._)

Fossil. Galiomellæ; _highly magnified_.]

In America, recent beds of this kind of great extent have been observed and examined by that distinguished microscopist, Dr. Bailey, Professor of Chemistry in the Military Academy at West Point: and the pages of that excellent scientific periodical, Silliman's _American Journal of Science_, are enriched with figures and descriptions of the microphytes of which they are mainly composed.

But the Tertiary formations contain strata of this nature, which far surpass in the abundance and variety of their organic contents, any of the modern deposits we have noticed. The _Polierschiefer_, or _polishing-slate_ of Bilin, is stated, by M. Ehrenberg, to form a series of strata fourteen feet in thickness, entirely made up of the siliceous shells of _Galionellæ_, of such extreme minuteness, that a cubic inch of the stone contains forty-one thousand millions. The _Berghmehl_ (_mountain-meal_, or _fossil farina_), of San Flora, in Tuscany, is one mass of these organisms.

In Lapland a similar earth is met with, which, in times of scarcity, is mixed by the inhabitants with the ground bark of trees, for food; some of this earth was found to contain twenty different species of algæ.

In the district of Soos, near Egra, in Bohemia, a fine white infusorial earth occurs, about three feet beneath the surface; this substance, when dried, appears to the naked eve like pure magnesia, but under the microscope is seen to be mainly constituted of elegant disciform cases of a species of _Campilodiscus_, of which figures are given, _Lign. 111, figs. 1, 2_.

Some beds of porcelain-earth M. Ehrenberg found to be in a great measure made up of concentric articulated rings, entire and in fragments (see _Lign. 6_), which he believes to be bacillariæ.

[Sidenote: FOSSIL DIATOMACEÆ OF VIRGINIA.]

Fossil Diatomaceæ of the Richmond-earth; Virginia.--The town of Richmond, in Virginia, is built on strata of siliceous marl of great extent, which earth; highly magnified. have a total thickness, beneath and around the town, of more than twenty feet. These marls, whose organic composition was first detected by Professor W. B. Rogers, are referred by that eminent American geologist, to the older tertiary (_eocene_, or _miocene_) formations. They occupy considerable districts, spreading out into sterile tracts along the flanks of the hills, their siliceous character rendering them unfavourable to vegetation. The investigations of Dr. Bailey have shown that the frustules so abundant in this earth, consist of several species of Navicula (_Lign. 1, fig. 1, 1a_.), Galionella (_Lign. 1. fig. 3, 3a_.), _Actinocyclus_ (_Lign. 1, figs. 4, 5_), &c.

The most remarkable forms are disciform frustules, having their surfaces elaborately ornamented with hexagonal spots disposed in curves, and bearing some resemblance to the engine-turned case of a watch. _Lign. 7, fig. 2_, is a small segment of a disc, very highly magnified. These frustules vary in size from 1/100 to 1/1000 of an inch in diameter; they are named _Coscinodiscus_ (_sieve-like disc_), and there are several species: one less richly sculptured, _C. patina_, is figured _Lign. 7, fig. 6_. Circular bodies, with five or six lines radiating from the centre to the circumference, like the spokes of a wheel, hence named _Actinocyclus_ (_Lign. 7, figs. 4, 5_), and spicules of Sponges, are also abundant.

from the Richmond-earth; _highly magnified_.

_Tertiary. Virginia._

Fig. 1.--Navicula. 1_a_. Side view.

2.--Coscinodiscus radiatus; a portion of the circular shield.

3.--Galionella sulcata; the upper figure shows the transverse
face of one of the frustules.
3_a_.--Three united cells viewed laterally.

4, 5.--Actinocyclus. Two species.

6.--Coscinodiscus patina; transverse view.
6_a_. Lateral view.
]

[69] As the term _Infusorial-earth_ must be abandoned, it will be convenient to substitute a name simply expressive of the nature of the most abundant organisms that enter into the composition of these deposits: that of _Microphyta_, or _Microphytes_, (from μικρος, _mikros_, small, and φυτον, _phyton_, a plant), signifying very minute vegetables, may perhaps be admissible: in this sense the word microphytal is employed in these pages.

When a few grains of the marl are prepared, and mounted on a glass, almost all these varieties will be manifest, so largely is this earth composed of organic structures; in fact, very few inorganic particles are intermixed, the merest pellicle left by the evaporation of a drop of water in which some of the marl has been mixed, teeming with the most beautiful structures.

At Petersburg, in Virginia, a sandy marl occurs, interstratified with deposits which, from their shells, are referred to the older tertiary formations. Probably this marl is a continuation of that of Richmond, but it is full of many new forms, associated with those common in the earth of the latter locality.[70]

[70] Dr. Bailey, with great liberality, has so amply supplied myself and other observers with specimens of these deposits for examination, that the fossils above described are familiar to all British microscopists. Figures of many of those organisms are given in the American Journal of Science.

It is an interesting fact, (first observed by Mr. Hamlin Lee,) that the common Scallop (_Pecten maximus_), as well as the Barnacle (_Balanus_), feed on diatomaceæ, and their stomachs generally contain numerous cases of Coscinodisci, Dichtyochi, Actinocycli, &c.: a slide prepared and mounted with the contents of the stomachs of these mollusks, presents an assemblage of forms identical with those found in the tertiary earths of Virginia.[71]

[71] See my "Thoughts on Animalcules," p. 103.

In the mud of the quicksands on the shore at Brighton, Mr. Reginald Mantell found recent Coscinodisci, &c. associated with fossil polythalamia that had been washed out of the chalk, and precipitated with the frustules of the recent diatomaceæ, into the sediments now in progress.

The prevalence of marine and fresh-water forms in the same deposit is not unusual; and the remarks of Dr. Bailey on this fact are so pertinent, that I insert them, as a salutary caution against hasty generalizations on subjects connected with these investigations. After describing a species of Galionella (_G. moniliformis_), as an inhabitant only of salt and brackish water, and stating that he had also found it sixty miles up the Hudson River, near West Point, Dr. Bailey observes--"The Fauna and Flora of the Hudson at this place would, if in a fossil state, be rather puzzling to the geologist, on account of the singular mixture of marine and fluviatile species. While _Valisneria_ and _Potamogeton_ (two common fresh-water plants), grow in such vast quantities, in some places, as to prevent the passage of a boat, and the shore is strewn with fluviatile shells (such as Planorbis, Physa, &c.) in a living state, yet the above plants are entangled with Algæ (sea-weeds), and marine parasitic zoophytes; while the rocks below low-water mark are covered with Balani (_barnacles_) and minute corallines, and the marine Flora is represented by vast quantities of very elegant sea plants."[72]

[72] American Journal of Science, vol. x. p. 41.

* * * * *

I must here close this extended notice of the fossil remains of a class of vegetable organisms, which, though for the most part invisible to the unassisted eye as individual forms, constitute by their inconceivable multitudes an important element in the formation of sedimentary deposits. The fact of their having been formerly treated of as animalcules, and generally regarded as belonging to the animal kingdom, rendered a full consideration of the phenomena necessary, in order to place the subject before the reader in a clear and comprehensive point of view.[73]

[73] As both the recent and fossil frustules of Diatomaceæ are beautiful objects for the microscope and polariscope, they are in much request. Specimens mounted on glass slides may be had of Mr. Topping, and Mr. Poulton. See Appendix.

Confervites.--The cellular aquatic plants named Confervæ are sometimes found in transparent quartz pebbles, and in chalk, appearing as delicate simple or branched filaments, which, by the aid of the microscope, are seen to be articulated. Seven species are described by authors, but the vegetable nature of some of these is doubtful. A beautiful species in Chalk, first noticed by the late Samuel Woodward, Esq. (author of the Geology of Norfolk), is here figured.

_Chalk. Norfolk._]

[Sidenote: FOSSIL FUCOIDS.]

Fossil Fucoids.--Of the tribe of Algæ which comprises the sea-weeds that are not articulated, many fossil species occur in very ancient, as well as in modern, fossiliferous deposits. In the Lower Silurian rocks of North America, beds of limestone of great extent are full of a large digitated Fucus (_Fucoides Alleghaniensis_).[74] The Firestone or Malm-rock of Bignor in Sussex abounds in a ramose variety (_Fucoides Targionii_, _Vég. Foss._ p. 56), of which specimens are figured in the vignette of this volume, and in _Lign. 9._

[74] Figured and described in Dr. Harlan's Medical and Physical Researches: Philadelphia, 1835, p. 393.

Chondrites.--These fossil algæ approach nearest to the living species of _Chondrus_ (hence the name of the genus). The frond is thick, branched, dichotomous, with cylindrical or claviform divisions, with a smooth surface and without tubercles. The substance of the Bignor fossils is a white friable earth, which strikingly contrasts with the dark grey malm-rock that forms the matrix. As the Sussex Chalk Chondrites appear to be distinct from the Tertiary species named by M. Brongniart _C. Targionii_, I have, at the suggestion of Mr. Morris, substituted _C. Bignoriensis_, to indicate the locality in Sussex in which I discovered it forty years since. In the chalk-flints ramose fuci occasionally occur, but not in a state of preservation that admits of the determination of the forms of the originals.

Chondrites Bignoriensis; _nat._

_Malm-rock. Bignor, Sussex._]

The tertiary marls and limestones of Monte Bolca yield several beautiful species of Algæ, one of which is figured in _Lign. 10_. It is referred to the fossil genus _Delesserites_ (Sternberg), which includes those algæ that have thin, and flat or undulated, smooth, membranous fronds, with a median rib.

Of the little plants comprised in the class of cellular cryptogamia, which have stems, leaves, and fructification, but no true vessels, two or three species of Moss and Liverwort have been met with in tertiary strata. Mosses as well as Fuci are occasionally imbedded in quartz pebbles, in which they appear of their natural colour, and apparently floating in the transparent medium. A beautiful green moss, with a Conferva twined round its base, is figured _Lign. 11_ , p. 104, from a specimen described by the late Dr. Macculloch. It is supposed to be related to _Hypnum_ (_Geol. Trans._ vol. ii.).

[Sidenote: MOCHA-STONES.]

Moss-agates and Mocha-stones.--The beautiful siliceous pebbles called Moss-agates, and Mocha-stones, will so often come under the notice of the collector, that, although but extremely few, if any, of these objects contain organic remains, the arborescent substances they inclose being merely metallic oxides, a few remarks on their nature may be expected. The late Dr. Macculloch paid considerable attention to the investigation of these bodies, and believed that some of the objects imbedded in the pure and compact quartz were really of vegetable or animal origin; the specimen figured _Lign. 11_ is of this kind; the fossils being apparently cellular cryptogamous plants. In _Geol. Trans_, vol. ii., other examples are figured and described by the same sagacious observer. Mr. Bowerbank is of opinion that spongeous structure enters into the composition of almost all the moss-agates, and I have no doubt that in some instances such organisms are present: but in by far the greater number of agates and mocha-stones the inclosed bodies are mere crystallizations; they are arborescent or dendritical oxides of manganese, copper, chlorite, iron, &c.

_Monte Bolca._ (_Vég. Foss. Br._)]

Moss and Conferva, in transparent quartz, × 3.]

M. Brongniart, who carefully examined a great number of agates and pebbles, with the view of determining if vegetable substances were ever imbedded in them, could not detect a single instance in which the apparent mosses, confervæ, or algæ, were organic; in every case the mineral origin of the pseudo-vegetation was, in his opinion, unequivocal. Some of the beautiful green arborescent bodies in quartz pebbles, even under the microscope, present so close a resemblance to confervæ and mosses, that it is difficult to persuade oneself they are not vegetable structures; but the observations of M. Brongniart appear to me conclusive as to their mineral nature.[75] With the exception of three or four species of _Jungermannia_, and four or five of _Muscites_ in Amber, M. Brongniart states that he knows but one true fossil plant of the family of Mosses; the _Muscites Tournalii_ from the fresh-water tertiary deposits of Armissan.

[75] See Histoire des Végétaux Fossiles, pp. 29-34.

Vascular, or Acrogenous Cryptogamia.--These plants, as the name implies, possess a more complicated structure than the preceding, having vascular tissue as varied as in the phanerogamia.

Equisetaceæ.--The common species of Equisetum, or Marestail, is a plant that grows in marshy tracts, and on the banks of ditches and rivers; it has a jointed stalk, garnished with elegant sheaths which embrace the stem, and verticillate linear leaves: it attains a height of two feet, and is half an inch in diameter. In the fossil state there are many plants allied to the Equisetum, but only a few that are generically the same.

_Wealden. Pounceford._ _nat._

Fig. 1.--A stem, having two sheaths, and a bud at the lowermost joint.

2.--Stem of a young plant, with sheaths, preserved in pyrites.

3.--Stem, with the cryptogamous head or upper end.
]

[Sidenote: EQUISETITES.]

Equisetum Lyellii, _Lign. 12_.--A species which I discovered in Wealden limestone, at Pounceford (_Geol. S. E._ p. 245), must have closely resembled the _Equisetum fluviatile_: it has an articulated cylindrical stem, and regularly dentated sheaths, embracing the stem at the joints.

A transverse slice of the stem exhibits under the microscope a cellular structure filled with calc-spar, and forms a beautiful object when viewed with the polarizing apparatus. This plant occurs in many localities of the Wealden in Sussex and Kent; from the railway cuttings near Tonbridge, I collected several fine specimens; it is met with also in the cliffs near Hastings.

Equisetites columnaris. _Lign. 13_.--A gigantic species of Equisetum abounds in the strata of the lower division of the Oolitic or Jurassic formation of Yorkshire, and many fine specimens have been collected, especially from the vicinity of Whitby. In the sandstone of the Inferior Oolite of the Cleveland Hills, Yorkshire, numerous stems of this colossal marestail have been observed standing erect, as if occupying the position in which they grew; the same fact was also discovered at Carlton Bank, near Stokesly, forty miles from the coast. In both localities fossil shells of fresh-water mussels (_Uniones_) were associated with the vegetable remains.

(Ad. Brongn. Pl. 13.)

_Lower Oolite. Whitby._

Fig. 1.--Portion of a stem, showing two articulations, and an
intermediate constriction. 1/3 _nat._

2.--A few of the denticulations produced by the sheath, _nat._
]

This plant is a true equisetum, differing chiefly from existing species in its gigantic size and arborescent character. The sheaths surrounding the stem, and the verticillate linear leaves, are preserved in some examples: and in all, the furrows left by the imprints of the sheaths are more or less strongly impressed. The stem is not channelled throughout, as in _Calamites_, the carboniferous plant whose stems at first sight might be mistaken for those of Equisetites, but which are entirely distinct, as will be explained hereafter. The Equisetites columnaris is peculiar to the Oolite; it does not occur in the coal-measures. Specimens have been discovered which indicate a height of twenty feet, and a diameter of several inches.[76]

[76] See Hist. Vég. Fossiles, p. 115.

A small species of Equisetum (_Eq. Brodiei_[77]) occurs in the insectiferous limestone of the lower Lias, at Strensham, Worcestershire, associated with the foliage of fresh-water endogenous plants resembling the _Potamogeton_, or pond-weed, and of supposed dicotyledonous vegetables.

[77] Prof. Buckman, in Geol. Journal, vol. vi. p. 413.

1/3 _nat._

(Ad. Brongniart. Pl. 14.)

_Coal Formation. Yorkshire._

Fig. 1.--Part of a stem, showing the tubercles for the attachment
of leaves.

2.--A portion of the same on a larger scale.
]

[Sidenote: CALAMITES.]

Calamites. _Lign. 14, 15_.--Stem articulated, regularly furrowed longitudinally, the articulations naked, or studded with tubercles.

The plants of this genus were supposed to be related to the marestail, but to differ in the absence of the encircling sheaths, and in being uniformly striated; but an examination of specimens in a better state of preservation than those previously known, shows their affinity to the gymnosperms. Some of the species are of a gigantic size, being from one to three feet in diameter, and from thirty to forty feet in height. Calamites abound in the coal formation, and must have constituted an important feature in the forests of the carboniferous period; they occur also in more ancient deposits, and some species belong to the earliest terrestrial Flora of which any vestiges are known. In most instances when specimens are found lying in the same plane with the strata, they are pressed flat, but those occurring in a vertical position retain their natural cylindrical form. An outer crust or cylinder of coal generally invests the stem, but traces of the internal structure are rarely preserved.

The Calamite consists of a large central column of tissue, surrounded by a ligneous cylinder. The central part has in most instances perished after the death of the plant, and the cavity thus left been filled up with mineral matter. As the hollow ligneous zone is almost always carbonized, and very friable, it is seldom attached to the cast, and consequently the surface of the latter is generally jointed and ribbed.

The true external surface of the cortical investment is marked with longitudinal striæ, without any indications of joints or constrictions; but the position of the original articulations is indicated in some specimens by the _presence of small verticillate scars, to which leaves were appended_[78] as in the example figured by M. Brongniart, of which _Lign. 14, fig. 1_, is a reduced figure.

[78] See Mr. Dawes, "On the Structure of Calamites," Proc. Geol. Soc, 1851, vol. vii. p. 197.

Fig. 1.--Calamites radiatus, with the remains of one of the
sheaths.--1/2 _nat._

2.--Stem, with remains of roots.--1/2 _nat._

3.--Calamites approximatus, showing the curved lower end of the
plant.[79]--1/5 _nat._
]

[79] This specimen has been inadvertently drawn with the base uppermost.

The stellate appearance on the upper part of the stem figured in _Lign. 15, fig. 1_, is produced by the zone of leaves which surrounded the joint: this character is entirely distinct from the sheath of the Equisetum shown in _Lign. 12_. This specimen points out the importance of carefully examining and preserving the stone around fossil stems; had this precaution been lost sight of in this instance, no knowledge would have been obtained of this important botanical character. It is rarely that any traces of the roots remain; the fossil figured (_fig. 2_) is from the _Foss. Flor._ A beautiful example of the foliage of a species of Calamites is represented in _Lign. 59, fig. 2_.

Upright stems of Calamites occur in the Coal formation near Pictou, in North America; and in one example a group of ten or twelve stems, covering an area of two square feet, sprung from one root.[80]

[80] Dawson, Geol. Proc. vol. vii. p. 195. See Sir C. Lyell's Travels in North America, vol. ii. p. 195.

* * * * *

[Sidenote: FOSSIL FERNS.]

Filicites, or Ferns.

We now arrive at the consideration of one of the most interesting families of the vascular cryptogamia that adorned the Flora of the ancient world, and the living species of which impart beauty and elegance to the scenery of the countries where they prevail. The most essential character of these vegetables, is that of developing their fructification on the leaves; a fact familiar to every one who has even but cursorily examined the Polypody growing on our walls, or the Brake of our hedge-rows and commons. The largest species of British ferns scarcely exceed four or five feet in height; but the arborescent or tree-ferns, of warm climates, attain an altitude of from thirty to forty feet. There is too this peculiarity in the arborescent forms, that while in our indigenous species the leaves surround the stem, and incline towards the upper part of the plant, the foliage of the former bends downwards, and spreads out from the crown, or summit, into an elegant canopy.

_Coal Shale. Ohio._

_a._ The Stem.

_b._ Leaf-stalk, or petiole.

_c._ Leaf, or frond, which is bipinnate.

_d._ _e._ Leaflets, or pinnæ; the upper, _d_, are entire;
the lower, _e_, are pinnatifid.

_f._ The pinnules, lobes, or segments.

_g._ The midrib, or median vein.

_h._ The veins. The veins are introduced in the leaflets,
_d_; but in the lower ones, _e_, the midribs
only are marked.
]

The leaves of our branched ferns are persistent, and when shed, the markings left by their attachment to the stalk are soon obliterated. In the arborescent ferns, on the contrary, the petioles become detached from their bases, and fall entire, leaving scars or cicatrices on the stem; and these impressions are so regularly and symmetrically disposed, as to afford characters by which the trunks may be distinguished from those of other trees. The stems of the tree-ferns are therefore easily recognized in a fossil state externally, by their cylindrical forms without ramification, and by the regular disposition and peculiar character of the scars left by the separation of the petioles; and, internally by that peculiar zone, formed of bundles of ligneous tissue inclosed in sheaths, which encircles the central axis, as shown in the transverse sections in _Lign. 2_, _ante_, p. 62. The leaves may be identified by the form of their segments, which are disposed with remarkable regularity, and have a peculiar mode of subdivision; and above all, by the delicacy, evenness, and distribution of the veins. There are upwards of two thousand species of living ferns, and in the fossil kingdom the number is considerable; more than two hundred have been collected from the carboniferous formation. The recent tree-ferns are confined almost exclusively to the equinoctial regions; humidity and heat being the conditions most favourable to their development (_Vég. Foss._ p. 141. _Bd._ p. 461. _Wond._ p. 727).

From the elegance and diversity of form of their foliage, fossil ferns are the most remarkable and attractive vegetable remains in the ancient strata. The greater number are from the coal deposits, the fern-leaves generally occurring in the schists or shales that form the roof of the beds of coal. Many of the strata are made up of carbonized fern-leaves and stems closely pressed together. The roof of a coal-mine, when newly exposed, often presents a most interesting appearance, from the abundance and variety of leaves, branches, and stems, that occur either in relief, or impressed on the dark glossy surface. The specimens selected for illustration exhibit the principal modes of venation on which the genera are founded.

* * * * *

The fossil genera have been established by M. Ad. Brongniart, from the form of the leaves and the characters of their venation; that is, the distribution of the vessels. In the following descriptions some botanical phrases are necessarily employed; a few terms of frequent occurrence are explained in _Lign. 16_.

Pachypteris[81] (_thick-fern_). _Lign. 17._--In this genus from the lower Oolite, the fronds are pinnated, or bipinnated, the leaflets entire, without visible veins, having but a single midrib, and contracted at the base. The absence of veins, and the leaflets not being lobed, are the essential generic distinctions.

[81] The names of the genera are derived from _pteris_, fern, to which prefixed a term indicative of the peculiar characters.

_Inferior Oolite. Whitby._]

_Coal-shale, Waldenburg, Silesia._]

[Sidenote: FOSSIL FERNS. SPHENOPTERIS.]

Sphenopteris (_wedge-leaf_). _Lign. 18_.--The leaves are twice or thrice pinnated, the leaflets wedge-shaped, contracted or narrowest at their base, and more or less deeply lobed: the lobes divergent and palmated: the veins radiating from the base.

The ferns of this genus are extremely elegant, and comprise upwards of forty species. A beautiful Sphenopteris (_S. affinis_, _Wond._ p. 716,) occurs abundantly in the fresh-water carboniferous strata at Burdie House, near Edinburgh;[82] another elegant form, in coal-shale, is represented in _Lign. 18_.

[82] See Dr. Hibbert's Memoir on the Strata and Fossils of Burdie House. 4to. 1835.

_Inferior Oolite, Scarborough._

A magnified vein of a leaflet, showing the fructification at the extremities of the lobes, × two diameters.]

It is so rarely that the fructification of any species of Sphenopteris is preserved in a fossil state that I am induced to figure a leaflet of a remarkable plant, of this genus from the fluvio-marine oolitic deposits of Scarborough. _Lign. 19_ is copied from the lithograph accompanying a notice of some rare plants from that locality, by the eminent botanist, C. J. F. Bunbury, Esq.[83]

[83] Geol. Journal, vol. vii. p. 179, pl. xii.

This fossil fern closely resembles certain species of _Dicksonia_ (natives of New Granada). Each segment of the leaflet or pinnate is dilated at the apex into a reniform _indusium_; no capsules are visible, the fructification being, probably, in a young state.

In the Wealden deposits, both of England and Germany, several species of Sphenopteris abound; one of which (_Foss. Tilg. For._ 1827), often occurs in the calciferous grit of Tilgate Forest, in a beautiful state of preservation: a small branch is figured in _Lign. 20_. This species is characterized by its slender and minutely divided wedge-shaped leaflets. The Sphenopteris Mantelli did not attain a considerable size; the largest stem I have seen indicated a plant of five or six feet in height. This Sphenopteris is sometimes associated with the remains of a beautiful plant of the genus _Alethoptris_,[84] the leaflets of which, in some examples, bear the fructification. (_Wond._ p. 394, _Lign._ 89.)

[84] _Alethoptris elegans_ of Dr. Dunker. Mon. Norddeutschen Weald, pl. vii. _fig. 7_.

_Oolite, near Scarborough._]

Cyclopteris (_round-leaf_). _Lign. 21._--The frond is simple and entire, or but slightly lobed at the margin, and generally orbicular, or kidney-shaped: there is no midrib; the veins are numerous, equal, and dichotomous, or forked, and radiate from the base. The form and disposition of the veins resemble those of some living species of fern; the absence of a median rib, or vein, is the most striking character of this genus. The fructification is supposed to have been marginal.

[Sidenote: FOSSIL FERNS. NEUROPTERIS.]

Neuropteris (_nerved-leaf_). _Lign. 22._--The fronds are pinnate or bipinnate; the leaflets more or less ovate or cordiform and entire, adhering to the rachis by their centre only; veins very fine, arched, rising obliquely from the base of the leaflet; the midrib does not extend' to the apex of the leaflets, but terminates by subdividing into veins.

_In Coal-shale, Yorkshire._]

This is a very numerous genus, comprising thirty or more species, which are principally found in the coal-shale. Some of these plants bear a general resemblance to the _Osmunda regalis_, but differ in their essential characters; their leaflets often form the nuclei of ironstone nodules.

Glossopteris (_tongue-leaf_). _Lign. 23._--Leaves simple, sub-lanceolate, gradually contracting towards the base; midrib thick at the base, and vanishing towards the apex of the leaf; veins very fine, curved, oblique, frequently dichotomous, sometimes reticulated, or anastomosing at their base. The plants of this genus resemble the ferns with simple leaves. A few species only are known; of these, two are from the coal-shale, one from the Lias, and one from the oolite.

_Oolite, Scarborough._]

_Coal-shale of Saxony._]

Odontopteris (_tooth-leaf_). _Lign. 24._--Leaf bipinnate, the leaflets adhering to the rachis or stalk by their whole base, which is not contracted; the veins equal, simple, dichotomous, arising side by side from the base of the leaflet; no distinct midrib. In their general aspect these plants resemble some South American species of Osmunda. Five species only are known, all of which belong to the most ancient coal strata.

Anomopteris (_anomalous fern_--so named because the plants differ from all recent and fossil ferns). _Lign. 25._--Leaves deeply pinnated; leaflets very long, entire, linear, traversed by a distinct midrib, equal throughout; secondary veins simple, perpendicular to the median vein, swollen at their free extremities, and not extending to the margin of the leaflet. But one species is known. These leaves are of great size, and doubtless belonged to some arborescent fern; in several examples the fructification is preserved. My collection contained a splendid specimen from near Strasburgh, presented by the late M. Voltz, which is now in the British Museum.[85]

[85] Petrifactions, p. 32.

_New Red Sandstone; Sultz-les-Bains, near Strasburgh._

Fig. 1.--Three leaflets of a very large frond.

2.--A portion magnified to show the fructification.
]

[Sidenote: FOSSIL FERNS. TŒNIOPTERIS.]

Tœniopteris (_wreathed fern_). _Lign. 26._--Leaves simple, entire, straight, with parallel margins, traversed by a strong midrib, which extends to the apex; secondary veins, simple or bifurcated at their base, and almost perpendicular to the median vein. These ferns are related to certain species of Polypodium. Three species are known; two from the Oolite, and one from a tertiary deposit. The specimen figured is a fragment.

_Stonesfield Slate._]

Fig. 1.--Pecopteris Murrayana; a pinnule with the fructification;
_magnified._ _Inf. Oolite, Scarborough._

2.--Pecopteris lonchitica. _Coal-shale, France._
]

Pecopteris (_embroidered fern_). _Lign. 27._--Leaves once, twice, or thrice pinnated: leaflets adhering by their whole base to the rachis, rarely by the centre only; traversed by a strong midrib, which extends to the apex; veins simple, or once or twice dichotomous, proceeding almost at right angles from the median vein.

This genus embraces a very large proportion of the ferns which have contributed to the formation of the coal, and whose leaves and stems are preserved in the associated strata. The originals of many species were undoubtedly arborescent, and attained a large size; some leaves four feet wide, and of a proportionate length, have been observed. More than one hundred species are determined. An American species (_Pecopteris Sillimani_) is figured in illustration of certain botanical terms, _Lign. 16_, _ante_, p. 110. Several species of Pecopteris occur in the fluvio-marine oolitic deposits near Scarborough, and leaves in fructification are not uncommon: _fig. 1, Lign. 27_, represents a leaflet slightly magnified.

_Wealden, Tilgate Forest._

Fig. 1 and 2.--Leaflets magnified, to show the reticulated venation.

3.--A fragment of a frond; _nat._
]

[Sidenote: FOSSIL FERNS. LONCHOPTERIS.]

Lonchopteris (_spear-leafed._) _Lign. 28._--Leaves many times pinnated; leaflets more or less adherent to each other at their base, traversed by a midrib; secondary veins reticulated.

The three known species which compose this genus resemble the living ferns of the genera Lonchitis, Woodwardia, &c. Two have been found in the coal-measures, and one species in the Wealden formation of England and Germany (_Foss. Tilg. For._ pl. iii.) This last appears to have been a delicate plant; for though fragments are very common in the micaceous grits and clays, any considerable portion of a leaf is of rare occurrence. M. Graves found the same fern near Beauvais in France, in strata, which, from the presence of the fresh-water limestone called Sussex marble, are supposed to be referable to the Wealden epoch. This Lonchopteris is widely spread through the Wealden; and occurs also in the Greensand. Mr. Morris first observed it in the iron-sandstone of Shanklin Chine.[86]

[86] Geol. I. of W. 2d _Ed._ p. 230.

Fig. 1.--Phlebopteris[87] Phillipsii. _Oolite, Scorborough._

2.--Phlebopteris propinqua, _showing fructification_.
]

[87] Comptopteris of M. Ad. Brongniart.

Phlebopteris (_veined-leaf_). _Lign. 29._--Leaves pinnated; leaflets with the margin entire, or crenulated, the midrib strong; secondary veins anastomosing by arches, with large angular spaces, often unequally disposed; the finer veins are simple or divided; the apex sometimes free. The fructification is punctiform, and placed at the apices of the veins.

The foliage of these remarkable ferns has been mistaken for the leaves of dicotyledonous plants; but M. Brongniart has demonstrated that they belong to the present family. Six species have been found in the Oolite and Lias.

_Portion of a leaflet: the original 1-1/2 ft. long._

_Wealden? Scania._]

[Sidenote: FOSSIL FERNS. CLATHROPTERIS.]

Clathropteris (_latticed-leaf_). _Lign. 30._--Leaf deeply pinnatifid; leaflets elongated, traversed by a strong midrib extending to the apex; secondary veins numerous, simple, parallel, almost perpendicular to the midrib, united by transverse branches, which, with the finer veins, produce on the surface of the leaf a net-work of quadrangular meshes.

This genus was instituted by M. Brongniart, for the reception of some very large fern-leaves from the shale of Hoer, in Scania, which resemble in structure the foliage of the recent _Polypodium quercifolium_, a native of the East Indies, and the Moluccas. One leaf was four feet wide, and the leaflets, though imperfect, were eighteen inches long.[88]

[88] Hoer is a little village, situated nearly in the centre of Scania, a province in the southern extremity of Sweden. The Chalk formation appears in several parts of this district, and Carboniferous strata at Hoeganes. To the west of Hoer, there is a range of hills, composed of ferruginous grits, micaceous sandstones, clays, and beds of quartzose conglomerate. It is in these strata that the ferns and other terrestrial plants occur, and no animal remains whatever have been found in them; their geological position appears to be between the Chalk and the Coal, but on this point nothing positive is known. The general analogy of the plants with the group forming the Flora of the Wealden, led M. Brongniart to suppose that the deposits in question belong to that formation; and M. Nillson, of Lund, who examined my collection at Brighton, recognized, among some undescribed plants from Tilgate Forest, forms that he had collected from Hoer. See "_Observations sur les Végétaux Fossiles renfermés dans les Grès de Hoer en Scanie: par M. Ad. Brongniart._" _Ann. Sc. Nat._ 1825.

Many other genera of fossil ferns have been established from the form and venation of the leaves, and are described in _Brit. Foss. Flor._, and other British and foreign works.

Stems of arborescent Ferns.--Notwithstanding the profusion with which the foliage of many kinds of ferns is distributed throughout the coal formation, the undoubted stems of plants of this family are rarely met with; for the numerous tribe called Sigillariæ is now removed altogether from this class. It may, however, admit of question whether much of the foliage which, from the analogy of structure, has been referred to ferns, may not have belonged to those trees; for as in the animal kingdom, so in the vegetable, distinct types of living organisms are often found blended in the lost races; and as the stems of recent tree-ferns are even more durable than their leaves, it seems impossible to account for their absence in strata, that inclose entire layers of the foliage matted together. A few fossils, supposed to possess the essential characters of recent fern-stems, have been discovered, and arranged under the following genus.

[Sidenote: FOSSIL FERN-STEMS.]

Caulopteris (_fern-stem_). _Lign. 31._--Stems not channelled, marked with discoidal, oblong, or ovate scars, arranged longitudinally; vascular cicatrices numerous.

The fragment of stem here figured, resembles the trunks of some recent tree-ferns in its proportions, and in the number, disposition, and size, of the scars of the leaf-stalks; but these markings differ in their more lanceolate form, and pointed terminations, and in their peculiarly striated surface, from those of any known existing species.

Psarolites (_Silicified Fern-Stems_).--In the New Red sandstone, near Hillersdorf, in the neighbourhood of Chemnitz, in Saxony, silicified stems, apparently of tree-ferns, occur in great numbers. They are remarkably beautiful, and the organization of the original is so well preserved by the silex, that slices, examined by the microscope, display the peculiar structure almost as perfectly as if the plants were recent: transverse sections exhibit the arched bundles of vascular fibres which compose the ligneous cylinder, surrounded by the cellular tissue. From the stellated markings produced by sections of the vessels that compose the tissues, and which are visible to the naked eye, these fossils have obtained the popular name of _Staaren-stein_, or Star-stone. The external surface of the specimens I have examined has a ligneous structure, and is of a dark reddish brown colour; internally the stems are of a dull red, mottled with various tints of blue and yellow, from the infiltrated chalcedony with which the vessels are permeated.[89]

[89] See Pict. Atlas (pl. viii.) for coloured figures; and Org. Rem. vol. L plate viii. _figs._ 1-7. The reader will be amused by the perusal of the ingenious but unsuccessful attempt of the excellent author, Mr. Parkinson, to elucidate their nature. I have still a specimen which he presented to me more than thirty-five years since, as one of the most curious and perplexing fossils that had ever come under his notice.