Chapter 15

SPINIFERITES IN FLINTS.

Lign. 77. A group of Spiniferites in Flint.(Seen by transmitted light.)Fig.1.—A thin-translucent chip of flint;nat.2.—The same magnified, and viewed by transmitted light; showing a group of fiveSpiniferites.3.—The same more highly magnified.4.—Spin. ramosus; one of the animalculites seen in fig. 3, very highly magnified.5.—Spin. Reginaldi; one of the same group; × 300 diameters.6.—A variety ofS. ramosus; another of the same cluster ofSpiniferites.

Spiniferites(Xanthidium, Ehrenb.).Lign.77.—I propose to describe in this place those elegant and very minute bodies, that occur in great numbers in the chalk and flint, and which, on the authority of M. Ehrenberg, were regarded as identical with the siliceous frustules of the genus of fresh-water Desmidiæ, namedXanthidium[218](ante,p. 91.) Later and more correct observations have proved that the fossilsunder consideration entirely differ from their supposed homologues; their original substance not being siliceous, but flexible and membranous; and that instead of being spores of algæ, they are probably the gemmules either of porifera, or of polypifera.

[218]Several recent species of Xanthidium are figured inPlate IV.of this volume.

To avoid the perpetuation of the error by the retention of the botanical name of a recent genus of plants, for fossils whose vegetable origin is very problematical, and which are entirely distinct from their supposed analogues, I would substitute that of Spiniferites,[219]a term simply expressive of the general aspect of these bodies; that of a globe or sphere beset with spines. The appearance of these fossils will be understood by the examination of a group discovered by Mr. Reginald Neville Mantell, in a fragment chipped off from a flint pebble; and I will describe the mode by which these minute objects were detected, as it offers a good practical lesson for the young investigator.

[219]Fromspina, a spine, andfero, to bear.

The chip of flint is represented, of the natural size, inLign. 77, fig. 1; it was immersed in oil of turpentine for a short time, and then placed on a piece of glass, and examined with a moderate power, by transmitted light, the turpentine having rendered the translucent flint almost as transparent as glass; this appearance is shown infig.2; the organisms here represented are from1/300to1/500of an inch in diameter. The half-inch object-glass was next employed, andfig.3 gives the result. The quarter-inch object-glass, and a corresponding eye-piece, were then substituted, and by the adaptation of a camera lucida,figs.4, 5, and 6, were delineated. Asfig.5 proved to be a new species, it was named after its discoverer.

The specimens in flint, when rendered transparent and viewed by transmitted light under a high power, as shown inLign.78, and79, appear as hollow globular bodies, besetwith spinous processes, which in most species are fimbriated at the extremities. There is considerable variety in the form and length of the spines. InS. Reginaldi, these appendages are numerous, regular, short, and relatively thick: in an elegant species discovered by the Rev. J. B. Reade (Lign.79) they are long and palmated: in other kinds they are of intermediate size and proportions.[220]

[220]Excellent figures of several species are given in a Memoir by H. H. White, Esq. of Clapham, in the Trans. Microscopical Society, vol. i. p. 77.

Lign. 78.Spiniferites Reginaldi.(Magnified 500 diameters.)

Lign. 79.Spiniferites palmatus; in flint.(× 500diameters.)

The apparently torn and collapsed state of the body and arms of some examples first led me to doubt the siliceous nature of the original substance; and on my discovery of the soft parts of foraminifera in flint and chalk, Mr. Deane undertook to search for the so-called Xanthidia in chalk, that these bodies might be subjected to chemical analysis,[221]Mr. Deane succeeded in detecting all the usual species in the Dover chalk, by digesting some chalk in dilute hydrochloric acid, and mounting the residue in Canada balsam. In this state the shape of the body is that of a depressed sphere; many of the specimens appear to have a circular opening, and thearms or spines to be closed at the extremities. Upon pressure under water between two pieces of glass, they were torn asunder as a horny or cartilaginous substance would be, and the spines in contact with the glass were bent. Some after maceration in water several weeks became flaccid; a proof that they are not siliceous.[222]

[221]A torn and apparently shrunken specimen from chalk, is represented in my paper on Foraminifera;Philos. Trans.1846, p. 465.[222]Memoir on Fossil Xanthidia, by Henry Deane, Esq. Microscopical Journal, 1846.

[221]A torn and apparently shrunken specimen from chalk, is represented in my paper on Foraminifera;Philos. Trans.1846, p. 465.

[222]Memoir on Fossil Xanthidia, by Henry Deane, Esq. Microscopical Journal, 1846.

The real nature of these fossils must be regarded as still undetermined: their prevalence in the chalk-flints whose forms are derived from zoophytes, seems to countenance the supposition that the Spiniferites are the gemmules or early state of animals of this family; but I have never detected any organic connexion between them and the porifera with which they are associated; it is possible they may be the germs of the remarkable zoophytes we have next to examine.

VENTRICULITES.

Ventriculites.[223]Lign.80,81,82.—At every step of our review of the fossil zoophytes, I find myself embarrassed by the conflicting opinions entertained by naturalists, respecting some of the most abundant of the extinct forms; arising from the imperfect state of our knowledge as to the structure of the originals, which compels a comparison with recent types, from which, perhaps, the fossils differed essentially in their organization. This remark especially applies to the zoophytes which have given rise to the fungiform flints so well known to the inhabitants of the chalk districts of Sussex, as "petrified mushrooms," from their close resemblance in form to fungi: a specimen with this name inscribed on it in the cabinet of a friend first drew my attention to these curious fossils. InLign.80,figs.2, 3, 4, 6, 7, 8, 9, several flints of this kind are represented;figs.3, 6, 8, arefungiform;fig.7, is the upper part of a specimen, the stem having been broken off;figs.2 and 4, are examples of the lower part of the zoophyte; in all, there are openings at the base, and a groove on the margin or edge of the upper part in which the structure of the inclosed fossil is visible; upon breaking these flints, sections of a funnel-shaped body are exposed.

[223]Ventriculite; fromventriculus, a ventricle or sac.

Lign. 80. Flints, deriving their forms from Zoophytes.From the South Downs, near Lewes;1/6nat.Fig.1.—Choanites (?) Turbinatus.2, 3,4, 6, 7, 8, 9.—Flints, whose forms are derived from Ventriculites,provincially called "petrified mushrooms."5.—Spongites labyrinthicus.10.—Spongites flexuosus.

The origin of these fossils will be understood by reference to the four specimens delineated inLign.81. Infig.3, a fungiform flint, resemblingfig.6, ofLign.80, is seen in the lower part of a cup-shaped zoophyte; while above, and surrounding the flint, the impression remains of the reticulated outer surface, deeply coloured by a ferruginous tinge. Infig.4,Lign.81, a small turbinated flint, resemblingfig.4, ofLign.80, occupies the base, and three rootlets are seen emerging from it at a. InLign. 82, fig. 1, in which the chalk has been removed so as to expose the outer surface of the Ventriculite, a flint occupies the centre at c; abovewhich, the radiating reticulated structure is spread out on the chalk,a; the base, with its roots, is shown atb.

Lign. 81. Ventriculites radiatus;1/6nat.Chalk; near Lewes.Fig.1.—A perfect specimen in chalk, inverted, showing the external reticulated surface; the apex of the base projects in the centre.2.—Specimen expanded, displaying the inner surface, studded over with the openings of the cells or tubes.3.—AVentriculitein chalk; the lower part inclosed in flint.4.—Portion of aVentriculite; the stem towards the base is enveloped in flint, and three radicle processes spread from it into the surrounding chalk ata.

These specimens demonstrate that all the flints referred to, have been moulded in the cavities of cyathiform zoophytes; and that their diversity of figure has arisen from the amount of silex that happened to permeate the organism; if but a small proportion of silica in solution was present, then flints, likefig.4, were produced; if the quantity were sufficient to fill up a considerable part of the tissues of the original, fungiform flints, asLign. 80, fig. 3, andLign. 81, fig. 3, were the result. The disciform flints originated from the expandedexamples,Lign. 81,figs.1 and 2: and when the silex was insufficient to silicify the entire zoophyte, an annular flint, resembling a quoit, was formed.

Lign. 82. Portions of Ventriculites;1/4nat.Chalk, near Lewes.Fig.1.—A specimen, in which the middle is inclosed in a flintc; the external structure of the Ventriculite is seen ata, expanded on the chalk; and the pedicle with its roots is exposed atb. The figures are one-fourth the size of the originals.2, 3,5.—Chalk specimens, showing the external structure of stems of Ventriculites.4.—A siliceous cast of the cavity of a Ventriculite covered with papillæ, moulded in the orifices of the cells.

The form of the original was evidently that of a hollow inverted cone, terminating in a point at the base, which was attached by fibrous rootlets to other bodies. The outer integument was reticulated, that is, disposed in meshes, like net-work; and the inner surface studded with regular openings, apparently the orifices of tubular cells. The substanceof the mass appears to have been sufficiently flexible to expand and contract without laceration. This opinion is based on the fact, that in many specimens the zoophyte is a nearly flat circular disc (Lign. 81, figs. 1, 2); and in others a subcylindrical pouch. In the former state the outer reticulated structure is elongated, while in the latter, it is corrugated; hence I am led to conclude that the original possessed a common irritability, and was able to contract and expand like many of the flexible polypiaria. The openings on the inner surface are cylindrical, and very regular; the flints often present sharp casts of them, which appear like rows of minute pillars. When the flint filling up the cavity of a Ventriculite can be extracted, it is a solid cone, studded with papillæ, the casts of the cells, as inLign. 82, fig. 4.

In the flints, the substance of the Ventriculites is generally as translucent as that of the Choanites, and defined by its rich purple, sienna, or grey colour;[224]but towards the base and margin it is more or less calcareous; and in many examples the whole, or a large portion of the zoophyte, is in this state. But this fact does not invalidate the inference that the original was flexible; for in these instances the tissues may have been immersed in fluid chalk before their envelopment in flint,[225]The chalk specimens are commonly as friable and earthy as the surrounding stone, from which they are distinguishable by their ochreous colour.

[224]Pict. Atlas, pl. xlv.fig.9, represents a beautiful transverse section of the lower part of a Ventriculite in flint, richly coloured. Pl. xliii.fig.16, is a pebble containing the base of a Ventriculite; the orifices on the top have been produced by the transit of the radicle processes; for the fossil is drawn in an inverted position, a common error before the origin of these flints was ascertained.[225]A piece of sponge dipped in liquid plaster of Paris, and afterwards inclosed in a transparent substance, as glass, would present such an appearance.

[225]A piece of sponge dipped in liquid plaster of Paris, and afterwards inclosed in a transparent substance, as glass, would present such an appearance.

The stain always observable in the tissues of the chalk Ventriculites and other zoophytes, while the surroundingwhite limestone is uncoloured, may be explained by the chemical changes to which the decomposition of animal matter under such circumstances would give rise. If sulphuretted hydrogen were evolved from the putrifying zoophytes imbedded in calcareous mud containing iron in solution, the sulphur would enter into combination with the iron, the hydrogen escape, and a sulphate or sulphuret of iron be deposited, atom by atom, and thus impart colour and permanence of form to the original.

When the inclosed organisms in the flint nodules have perished, chalcedony, quartz crystals, or crystallized pyrites, sometimes of great beauty, are found occupying the cavities; in short, numerous modifications of the petrifactive process are beautifully exhibited in these common, but highly interesting, cretaceous fossils.

The species to which the previous remarks more immediately refer, is namedVentriculites radiatus; from the radiated appearance of the external integument; some of the expanded specimens are more than one foot in diameter.[226]

[226]The reader interested in the history of these objects should consult Foss. South Downs, p. 167, plates x, xi, xii. xiii. xiv. A memoir by the Author on these fossils, under the name ofAlcyonium chonoides, with four beautiful plates, was published in the Linnæan Transactions, vol. xi. 1821. TheVentriculitesare the only organic remains figured in Conybeare and Phillips's Geology of England and Wales, p. 76.

Lign. 83. Ventriculites alcyonoides.in Flint. Lewes.Ocellaria inclusa. König.Fig.1.—Portion of the surface of fig. 2, magnified.2.—The fossil body extracted from the flint, fig. 4.2a.—Transverse section of the same, showing a centralspot of flint, surrounded by tubular cells.2b.—Two of the cells of fig. 2a, highly magnified.4.—The hollow flint, from which fig. 2 was extracted; the papillæon the surface, are casts of the apertures of cells.

Ventriculites alcyonoides.Lign. 83.—Under the name of "Ocellaria inclusa," the late Mr. König[227]figured and described an elegant fossil zoophyte not uncommon in the chalk and flints of Sussex. This fossil is inversely conical, and somewhat resembles the cast of the cavity ofVentriculites radiatus, but a little attention will enable the collector to distinguish it. The flint that is moulded inV. radiatus, is surrounded by the substance of the zoophyte, and if found detached, with the investing material removed, shows no structure whatever, but simply a surface covered with minute papillæ. The present zoophyte is generally included in a nodule, and by a slight blow may be readily separated from the surrounding flint; it then has the appearance of a white calcareous cone, beset with regular cells, disposed in quincunx order (Lign. 83, fig. 2); leaving a conical cavity in the flint, which is covered with corresponding eminences (Lign. 83, fig. 4). Upon breaking the cone itself, it is found to consist of a dense reticulated structure, from one-eighth to a quarter of an inch in thickness (Lign. 83, fig. 2a), investing a solid nucleus of flint, the surface of the latter being covered with minute points, which are less regular thanthose on the cavity of the outer case. The specific name,inclusa, was suggested by this character; which, however, is only accidental, for the specimens imbedded in chalk, are simply surrounded by the stone. It is the calcareous nature of the fossil, which renders it so easily separable from the investing flint, while its cells afford numerous points of attachment, and these remain as casts in relief on the interior of the hollow case: I have not observed the same regularity of structure on the inner as on the outer surface.

[227]Icones Foss. Sect.fig.98.

The reticulated integument of this zoophyte resembles in structure that ofV. radiatus. With regard to the latter, I should state that Mr. Toulmin Smith[228]discovered that the inosculating fibres of the intimate tissue formed an octahedral plexus at each knot or point of union; and this structure Mr. Smith regards as peculiar to the Ventriculites, and states that he detected it in all the fossils he has arranged under the nameVentriculidæ. No spicula have been detected in the integuments.

[228]"On the Ventriculidæ;" a series of papers published in the Annals of Natural History, with many figures of cretaceous zoophytes. By Toulmin Smith, Esq.

Until more ample and satisfactory evidence is collected as to the nature of these fossils, the interests of science will be best promoted by allowing the question to remain sub judice, and restricting the term Ventriculites to those zoophytes which possess the general characters of the type to which the name was originally assigned; namely, a vasiform or subcylindrical framework, terminating at the base in a point, and fixed by radicle processes; the substance consisting of a plexiform fibrous tissue; externally constituting a reticulated integument, the meshes disposed in a radiating manner from the base to the periphery; the inner surface studded with open cells regularly arranged.

In the former edition of this work the Ventriculites were placed with the Polypifera from the structure of the openingsor cells, for these are so symmetrical, and disposed with so much regularity, as to present a closer analogy to the polype-cells of a coral, than to the large pores of a sponge. The doubts expressed by many eminent observers as to the correctness of this view, have induced me to insert this notice in the present section; leaving the true affinities of these organisms to be determined by future observers. Possibly we have in these fossils the relics of a tribe of zoophytes of an extinct type, that formed a connecting link between theporiferaand thepolypifera; however this may be, I will venture to affirm that no one who had seen the infinitely varied examples of these fossils that I have, would for a moment confound them, as some naturalists have done, with the Scyphiæ, and other simple amorphozoa.

Lign. 84.A Coral-polype in flint.× 500diameters.(Seen by transmitted light.)

Polype in Flint.Lign. 84.—I will here notice an exceedingly minute and interesting object, discovered by the Rev. J. B. Reade, in a flint containing vestiges of a Ventriculite, and which may possibly belong to this tribe of zoophytes. It must however be remarked, that there was nothing to show the collocation was not accidental. The drawing with which Mr. Reade favoured me, is engravedLign. 84. This object is unmistakeably a polype-cell, with some of the integument of the animal protruding, in the form of a shrivelled tube. The possibility of soft animal tissues being preserved in flint, will not now admit of question, as we shall show when treating of the Foraminifera. The record of this fact may load to the discovery of other fossils of a like nature.

Fossil Polypifera.

POLYPIFERA.

As we proceed in our investigations, the impossibility of rigidly adhering to a zoological classification based on the structure of organs, of which but few, if any, traces exist in the mineral kingdom, becomes more and more apparent; the durable skeletons or polyparia being the only materials from which the palæontologist can gather information, relating to the physiology of the extinct coral-animals which swarmed in the ancient seas, and whose petrified remains constitute a large proportion of the secondary and palæozoic calcareous rocks.

Numerous fossil genera have been established by various authors from the external form of the polyparium, or the disposition and structure of the cells; but a slight attention to this department of palæontology will disclose corals which differ essentially from the typical forms, and new genera and species will require to be added to the already extended catalogue. The few genera selected for the present work, will convey a general idea of the nature of this class of fossils. To ascertain the names of the species he may collect, the student must refer to works especially devoted to the illustration of the corals of particular rocks; as for example, those of the BritishCretaceousdeposits in the monographs of the Palæontological Society; of thePalæozoicinSil. Syst.; and in Prof Sedgwick's Synopsis of the Classification of the Brit. Pal. Foss.; of theMountain Limestonein Prof, Phillips's work; and those of Ireland in Col. Portlock's Geological Memoirs. Those of the palæozoic rocks of New York, are illustrated in Prof. James Hall's splendid work on the Geology of that State.

The fossil zoophytes included in this section present innumerable varieties of form and structure, but agree in theimportant character of having originated, (with but few exceptions,) from aggregations of those minute beings termed Polypes (many-feet[229]). The common Hydra (Wond.p. 600), or fresh-water polype, that inhabits pools and streams, is a familiar example of a free animal of this kind, consisting of a cellular gelatinous substance, in the form of a short tube, or pouch, surrounded at the upper margin by long tentacula, or feelers, which appear to the naked eye as delicate threads. ThePolypifera, properly so called, are groups of polypes, permanently united by a common integument or axis, each animalcule having an independent existence. A common support or endo-skeleton, termedpolyparium,[230]is secreted by the integuments, which varies in its nature from a mere gelatinous, or horny material, to an earthy, calcareous, and even siliceous substance, that remains when the polypes die, and their soft parts have perished. All the varieties of corals, &c. are nothing more than the durable structures of aggregated masses of such beings.

[229]A name derived from the tentacula, or processes, which in some species serve for prehension, and in others for respiration.[230]The basis, framework, or endo-skeleton, of these groups of animalcules is termed thepolyparium, orpolypidom(polype-habitation); those of a stony hardness are familiarly known as corals; these names, therefore, refer to the durable substance, and not to the animals themselves; but in familiar writing, the term Coral is often used to designate the entire living mass. The Red-Coral forms a distinct genus calledCorallium. In fossils, thepolypariumalone remains, except in very rare instances.

[229]A name derived from the tentacula, or processes, which in some species serve for prehension, and in others for respiration.

[230]The basis, framework, or endo-skeleton, of these groups of animalcules is termed thepolyparium, orpolypidom(polype-habitation); those of a stony hardness are familiarly known as corals; these names, therefore, refer to the durable substance, and not to the animals themselves; but in familiar writing, the term Coral is often used to designate the entire living mass. The Red-Coral forms a distinct genus calledCorallium. In fossils, thepolypariumalone remains, except in very rare instances.

It may here be necessary to notice a prevailing error, regarding the mode in which the substance called coral is produced. It is very generally supposed that Corals, particularly those bearing stars and cells, have been constructed by animalcules, in the same manner as is the honey-comb, by the Bee; and the expressions often employed by naturalists, of "the coral animalcules building up their rocky habitations," and "constructing their cells," have contributedto foster this error. But the processes are in no respect similar: the insect, under the guidance of an unerring instinct, resulting from its peculiar organization,constructsits cells; but the polype is incapable of forming, or even modifying, its support or cell in the slightest degree. The polypidom issecretedby the animal tissues, in the same manner as are the bones in the vertebrated animals, without the individual being conscious of the process. If a piece of white coral be immersed in dilute hydrochloric acid, the calcareous part is dissolved, and the secreting membrane, in the form of a flocculent substance, is seen attached to the undissolved part; even in some coralline marbles of incalculable antiquity, the animal membrane may, in this manner, be detected.[231]

[231]See Pict. Atlas, pl. xxxiv.fig.2.

From the delicate and perishable nature of many of the gelatinous zoophytes, numerous tribes may have inhabited the seas, which deposited the fossiliferous strata, and yet no indications of their existence remain; while, of others, but obscure traces of their structure are likely to be detected.

The Polypifera are separated into two natural groups or classes; viz. theAnthozoa(flower-animals), and theBryozoa(moss-animals), orPolyzoa.

The Anthozoa are polypes of the most simple type of structure. The body consists of a symmetrical gelatinous sac, capable of contraction and expansion, with one aperture or mouth, which is encircled by tentacula. The Hydra, or fresh-water polype (Wond.p. 600), is a familiar example of a single, locomotive, anthozoan animal. In the compound or aggregated forms, the body is either inclosed in a horny sheath (ex.Sertularia,Wond.p. 615), or is supported by a lamellated calcareous endo-skeleton (ex.Fungia,Wond.p. 623, pl. vi.fig.15), or the soft parts invest a stony axis (ex.Madrepora,Wond.p. 620), or a horny flexible framework (ex.Gorgonia,Wond.p. 616).

The Anthozoa are subdivided into three orders, which arebased on the peculiar characters of the polypes; theHydra, theActinia(Sea-Anemone,Wond.p. 622), and theAlcyonium(Dead-men's fingers,Wond.pl. v.fig.10), being respectively the type of 1. theHydroida, or Hydraform; 2. theAsteroidaor Alcyonian; and 3. theHelianthoida, or Actiniform zoophytes.

In the Hydroida the body in the compound species is implanted in a horny tubular sheath, and the polypidoms form branched corallines, which are fixed by the base to rocks, sea-weeds, shells, &c.

The Asteroida have a horny or calcareous axis, surrounded and inclosed by the soft parts which secrete it.

The Helianthoids, except in the simple free species, as the Actinia, have a lamellated calcareous polypidom, the plates of which radiate from a centre.

The calcareous secretions of the Anthozoa, especially of the Helianthoida, in a great measure constitute the mass of the coral-reefs and coral-islands of tropical seas. Their polypidoms, whether external or internal, maintain but little organic connexion with the compound soft substance. These zoophytes increase by gemmation or budding; some throw up germs from the disk, as in Astreadæ; others laterally, as in Caryophillidæ; and some spirally along the stem, as in Madreporidæ; examples of these modes of reproduction are often found in fossil corals. The increase of coral-rocks is produced by the continual formation of new masses, by the successive generations which spring up as it were from the bodies of their parents; layer upon layer, and tier upon tier, of Helianthoid polypidoms, are found to compose many of the coralline limestones of the palæozoic formations.

Fossil Anthozoa.—The first group of extinct corals to be noticed under this head is theGraptolitidæ, a family restricted to the Silurian rocks, and whose natural affinities have been much questioned; some palæontologists referringthem to thePennatulidæ, or Sea-pens, others to theSertulariadæ.[232]

[232]For a full consideration of this subject, refer to Prof. McCoy's Brit. Palæozoic Fossils.

GRAPTOLITES.

Lign. 85. Graptolites in Wenlock Limestone.(Murch. Sil. Syst.)Fig.1.—Graptolites ludensis.[233]1a.—Magnified view of a portion of the same.2.—Graptolites Murchisoni.2a.—Magnified portion offig.2.

[233]Ludensis, from Ludlow—to indicate the habitat of the fossils.

Graptolites.Lign.85.—These curious zoophytes abound in many of the Silurian deposits; they consist of sessile polype cells, arranged in one or two rows to a flexible stem, like the recent Sertularia, or Virgularia. Prof. McCoy refers them to the order Hydroida.

In a recent state these bodies were probably covered with a soft, or albuminous mass, studded with polype-cells, disposed in rows along the margins of the lateral, curved, grapple-like processes, as in the zoophytes termedVirgularia,[234]to which one kind bears a great analogy. If two specimens of theGraptolites Ludensisbe placed together, so that the elongated smooth edges be in apposition, the united stems will be seen to offer a general resemblance to the axis ofVirgularia mirabilis.

[234]See British Zoophytes, pl. xxiv.

M. Barrande divides the Graptolites into three groups or genera, which are defined as follow:—

Graptolites(proper), a single series of cells united together at the base, and adhering along the sides nearly to the orifice of each cell, as infig. 1a.Monoprionof M. Barrande.

Rastrites.—The axis reduced to a mere line, on which the cells are placed at relatively wide intervals, and but slightly inclined. These two genera are supposed to have been hydroid zoophytes, and related to the Sertularidæ.

Diprion(Diplograpsusof Mr. McCoy), cells in two series arranged along a central axis; these forms present a foliaceous appearance; they are presumed to resemble the existing genera Pennatula and Virgularia.

Graptolites have been found in strata of the same age in Norway, Sweden, and Scotland.[235]I have received slates literally covered with them, from the Silurian rocks of the United States, by the kindness of my friend, Benjamin Silliman, jun. Esq.

[235]Many species of Graptolites from the Lower Silurian rocks of the South of Scotland, are described and figured by Mr. Harkness in Geol. Journal for 1850, vol. vii. p. 58, pl. 1.

Sir R. Murchison remarks, that the nature of the strata in which these remains occur in Radnorshire, indicates a condition of the sea, well suited to the habits of the family of Pennatulidæ, or Sea-pens; for the recent species live in mud and slimy sediment, and the fossils are imbedded in a finely levigatedmud-stone, which, from its structure, must have been tranquilly deposited.

I will next describe the single lamellated Anthozoa, and afterwards notice those corals which consist of an aggregation of radiated cells, either frondescent, or disposed in solid masses.

FUNGIA. ANTHOPHYLLUM.

Fungia(Wond.p. 623).—The corals thus named, from their supposed resemblance to fungi, are of a depressed form,and have the under surface scabrous; they are divided above by numerous lamellæ, or plates, which radiate from a central, oblong depression.

When living, the solid stony polyparium is enclosed in the gelatinous mass by which it was secreted, and there are numerous tentacula around the central cavity, or sac. These zoophytes may be compared to theActiniæ, or Sea-Anemones, from which they differ only in having a calcareous axis, while the Actiniæ have a tough albuminous integument. (Wond.pl. vi.fig.15, represents the living animal; andLign.141,fig.2, p. 641, andLign.58,fig.4, two fossil species).[236]

[236]Fungia numismalis. Pict, Atlas, pl. xxxvi.fig.6.——— polymorpha. Ibid. pl. xliii.fig.1—4; pl. xlv,fig.11.

[236]

Fungia numismalis. Pict, Atlas, pl. xxxvi.fig.6.——— polymorpha. Ibid. pl. xliii.fig.1—4; pl. xlv,fig.11.

Anthophyllum Atlanticum.Lign. 88. fig. 4.—In the arenaceous strata of the United States, which the researches of Dr. Morton, of Philadelphia, have proved to be the equivalents of the European Cretaceous formation, a single lamellated coral is not uncommon. It is evidently related to the Fungiæ, and has been named as above by Dr. Morton.

Turbinolia Königi(Wond.p. 320).—Polyparium turbinated, striated externally, detached, base not adhering; cell single, radiated.

This genus occurs in all the fossiliferous deposits: a small, well-marked species is frequently met with in the Galt, of which subdivision of the cretaceous strata it is a characteristic fossil. It is figuredWond.Lign.58,figs.1, 2.[237]

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