Chapter 16

[237]Turbinolia complanata. Ibid. pl. xxxvi.fig.9.————— mitrata. Ibid. pl. xxxvi.fig.10.

[237]

Turbinolia complanata. Ibid. pl. xxxvi.fig.9.————— mitrata. Ibid. pl. xxxvi.fig.10.

Caryophyllia centralis(Lign. 89 figs. 1, 2:Lign. 88, fig. 5).—Polyparium turbinated, or cylindrical, simple or branched, longitudinally striated, fixed by the base; cells lamellated.[238]

[238]Monocarya (of Lonsdale), Dixon's Fossils, p, 244.

A small recent species (C. cyathus), is very common in the Mediterranean, and frequently seen in collections: it iscyathiform, and the base by which it is attached to other bodies, is broad and spreading; the newer tertiary deposits of Sicily contain this species in abundance.

A Caryophyllia, bearing a general resemblance to this species, is common in the chalk, and occurs in beautiful preservation (Wond.Lign.58,fig.3).[239]

[239]C. centralis, Pict. Atlas, pl. xxxvi. figs. 15, 16.C. annularis, ibid. pl. xxxvii.fig.5.

[239]

C. centralis, Pict. Atlas, pl. xxxvi. figs. 15, 16.C. annularis, ibid. pl. xxxvii.fig.5.

Branched Caryophylliæ are found in the Coralline Oolite and Dudley Limestones (Sil. Syst.pl. xvi.). A large proportion of the Coral-rag of the Middle Oolite is composed of a branched species (C. annularis) of this genus;Lign.88,fig.5, represents a specimen from near Faringdon.

Lign. 86. Favosites polymorpha.(Goldfuss.)Devonian limestone. Eifel.Fig.1.—Portion of a branch of the coral;nat.2.—Fragment, slightly magnified, with part of the surface brokenaway below, exposing the central axis, and radiated arrangementof the cells, with their lateral pores.3.—Another portion, magnified, showing the polype-cells hollow.

Favosites polymorpha.Lign. 86.Lign. 88, fig. 3.—Polyparium stony, polymorphous, solid internally, compact,composed of a congeries of diverging or ascending parallel, contiguous, prismatic tubes, covered by pores, divided by lamellæ, and communicating by lateral foramina.

The corals of this extinct genus abounded in the Silurian and Devonian seas; the remains occur with those of other fossil zoophytes of that epoch in great numbers, both in Europe and North America. I have many beautiful examples from the Silurian rocks of the Ohio and Niagara, by favour of Dr. Owen, of New Harmony, and Dr. Yandell, of Louisville, in which the cells are filled up with calcareous spar. The varied markings on many of the Babbicombe marbles, and Torquay pebbles, are derived from the enclosed Favosites (Wond.p. 643).

Another species (Favosites Gothlandica) occurs in masses of a subconical shape, and is common in some of the Silurian limestones. A fragment, to show the structure, is figuredLign. 88, fig. 3.

CATENIPORA. SYRINGOPORA.

Catenipora(Wond.p. 644,fig.3).—Polyparium hemispherical, composed of vertical anastomosing lamellæ; cells tubular, oval, terminal, united laterally. The oval form of the cells when united laterally, and the flexuous disposition of the lamellæ, give rise in transverse sections to elegant catenated markings, from which appearance the fossil has received the name ofchain-coral.[240]The species figured (C. escharoides) inWond.is common in the Silurian limestones, and sometimes forms hemispherical masses more than a foot in diameter. The chain-coral is extensively distributed through the Silurian rocks of the United States. Coloured figures of this exquisitely beautiful coral are given inPict. Atlas, pl. XXXV.

[240]Org. Rem. vol. ii. pl. iii. figs. 4, 5, 6.

Syringopora ramulosa.Lign.88,fig.2.(Wond.p. 641.) These corals bear a general resemblance to the Organ-pipe Coral of Australia. The polypidom is composed of long, cylindrical, vertical tubes, distant from each other, and connectedby transverse tubular processes; the cells are deep and radiated by numerous lamellæ.

The external aspect of these fossils is that of a cluster of cylindrical pipes, more or less parallel, connected by short transverse branches. They are theTubiporitesof Mr. Parkinson, who has given admirable figures of several specimens.[241]In these fossil corals that excellent observer first detected the animal membrane. A slab of marble, whose markings are produced by the section of the inclosed tubes of a Syringopora, is represented,Wond.p. 644,fig.2. The Mountain limestones of Derbyshire, and of Clifton, on the banks of the Avon, contain figured marbles of this kind, which are manufactured into vases, tables, &c. The genus is extinct.

[241]Pict. Atlas, pl. xxxv.fig.1. Syringopora geniculata, Pict. Atlas, pl. xxxiv.

Lithostrotion Columnaria(Wond.p. 641,fig.8).—Polyparium massive, solid, composed of aggregated, contiguous, parallel, prismatic tubes, each terminated by a star: cells shallow, multi-radiate, stelliform.

Species of this extinct genus are common in the mountain limestone, in large masses, which, from the pentagonal form, and parallel arrangement of the tubes, appear like clusters of miniature basaltic columns.[242]

[242]Lithostrotion striatum, Pict. Atlas, pl. xxxvii. figs. 5, 6.

CYATHOPHYLLUM.

Cyathophyllum.Lign.87,figs.1, 2.(Wond.p. 641,figs.1, 3.)—Polyparium turbinated, simple or compound, internal structure transversely chambered or lamellated; cells polygonal, radiated, depressed in the centre.

The corals of this genus are so abundant in the Silurian rocks, that the seas of that epoch must have swarmed with them. The simple turbinated forms are often several inches long, and being somewhat curved, have obtained the popular name of "petrified rams-horns."

Upon slitting one of these corals vertically, as inLign.87,fig.1, the axis of the polyparium, beneath the cell, is foundto consist of thin transverse partitions, constituting a series of chambers.

In the compound Cyathophylla, the germs of young cells, occupying the disc of a parent cell, are often met with.Fig.3 represents a group of four germs on the parent cell, ofC. dianthus, a common and beautiful coral of the Dudley limestone.

Lign. 87, Corals from the Dudley Limestone.(Sil. Syst.)Fig.1.—Cyathophyllum turbinatum: an oblique longitudinal section,showing at a the transverse lamellæ, or cells, of the internalstructure.2.—The same species.3.—Cyathophyllum dianthus: a Specimen, with four young germsarising from the disc below.4.—The same species, with four adult cells.

These corals are also prevalent in South Devonshire, and many of the elegant marbles of Babbicombe are figured by the sections of these polyparia.[243]

[243]Cyathophyllum turbinatum, Pict. Atlas, pl. xxxvi.——————- fungites, ibid. pl. xxxviii.

[243]

Cyathophyllum turbinatum, Pict. Atlas, pl. xxxvi.——————- fungites, ibid. pl. xxxviii.

Associated with the Cyathophylla in the Silurian rocks, are certain corals that attain considerable magnitude, and which are principally distinguishable by their internal structure. Such areCystiphyllum, constructed of bladder-likecells, andStrombodes, composed of spirally contorted lamellæ, or plates (Sil. Syst.pl. 16(bis),fig.4). Other hemispherical masses, presenting on the surface concentric wrinkles, with very minute pores, are common at Dudley, and belong to the genusStromatopora.

Lign. 88. Fossil Corals.Upper Silurian, Dudley.[244]Fig.1.—Astrea ananas.1a.—A polished slice of Marble, formed ofAstrea pentagona.Devonian. Torquay.2.—Syringopora ramulosa.Mt. L. Derbyshire.3.—A Fragment ofFavosites Gothlandica.Ohio.(By Dr. Owen.)4.—Anthophyllum Atlanticum.Cret. U. States.(By Dr. Morton.)5.—Caryophyllia annularis.Oolite. Faringdon.

[244]Figured in Pict. Atlas, pl. xxxvii.fig.1.

ASTREA.

Astrea.Lign.88,figs.1, 1a.—Polyparium massive, irregular in shape, generally globular, formed by an aggregation of lamellated, radiated, shallow, polymorphous cells.

The corals of this genus are very numerous in the seas of the Tropics, and there are many species in the Oolite, and older secondary formations. The Astreæ, Caryophylliæ, Cyathophylla, &c., form the principal mass of the coralline limestones of the Oolite, termed theCoral-rag, from the abundance of these relics: being literally composed of an aggregation of large corals, the interstices of which are filled with shells, radiaria, &c., either whole, or in a comminuted state. The heaps of this limestone placed by the road-side, in the N. W. of Berkshire, appear like fragments of an old coral-reef, and attract the notice even of the most incurious observer. I have figured a specimen of Astrea,Lign.88,fig.1, and a polished section,fig.1a, from Clifton, a locality well known for the stupendous mural precipices of mountain limestone rocks, which yield beautiful examples of coralline marble.[245]The mode of increase of the Astrea is very curious; a subdivision takes place in the old cells, after the manner of the Infusoria; and among the fossils, a star or cell may often be seen in progress of division into two, three, or four stars (Sil. Syst.pl. xvi.fig.6). A living polype of this genus is figured,Wond.pl. vi.fig.13.

[245]Astrea arachnoides, Pict. Atlas, pl. xxxviii.fig.4.——— undulata, ibid, pl. xxxviii.fig.10.——— Tisburiensis ibid. pl. xxxviii. figs. 12, 13.

[245]

Astrea arachnoides, Pict. Atlas, pl. xxxviii.fig.4.——— undulata, ibid, pl. xxxviii.fig.10.——— Tisburiensis ibid. pl. xxxviii. figs. 12, 13.

A species of Astrea (A. Tisburiensis.Wond.p. 641,fig.9), is found in large hemispherical masses, completely silicified, at Tisbury, in Wiltshire. The transverse surface displays, in some specimens, beautiful white radiated stars, on a dark blue ground; and in others, the colours of the stars and ground are reversed. This silicified coral is obtained from a bed of chert, a foot in thickness, which is interstratified with the Portland limestone, this division of the Oolite being quarried around Tisbury.[246]

[246]See Catalogue of the Organic Remains of Wiltshire, p. iv. by Miss Etheldred Benett. 4to. 1831.

In the tertiary clays at Bracklesham Bay, Sussex, a beautiful small coral of this type (Siderastrea Websteri, Dixon's Foss. tab. i, 5), is found attached to flint pebbles.

Several species of this and the following genus, perfectly silicified, are found in the state of pebbles and boulders in the superficial soil of Antigua, and other islands of the West Indies, associated with the fossil palms, described in a former part of this work. Some of these corals are of great beauty, and polished sections exhibit the coralline structure most perfectly.[247]

[247]In the "Spongitenkalk," at Nattheim, near Heidenheim, all the corals are replaced by chalcedony.

Madrepora.—Polyparium arborescent or frondescent, porous, fixed; cells deep, with twelve rays, prominent, irregularly dispersed on the surface, and accumulated towards the terminations of the coral.

The term madreporite, or fossil madrepore, was formerly applied to all the branched fossil corals with radiated cells, but is now restricted to those which possess the above characters. The recent common species, figuredWond.p. 620, will serve to illustrate this genus. The elevated, branched Madrepores, with minute polygonal cells having twelve rays, the lamellæ of which are denticulated, are termed Porites, and are frequent in the Silurian strata (Sil. Syst.).

Millepora.Lign.89.—Coral ramose; cells very minute, distinct, perpendicular to the surface, giving the interior a finely striated fracture, disposed irregularly.

There are many fossil species of this genus, some of which are of considerable size. A small species from the mountain limestone is figuredLign.89,fig.7.[248]

[248]Millepora, Pict. Atlas, pl. xl.fig.6.

Lithodendron.Lign.70,fig.3.—Polyparium branched, formed of deep, cylindrical, elongated cells, which are terminal, and radiated, with a prominent central axis.

Large masses of corals of this genus, composed of clustersof branches, are imbedded in the mountain limestone of Derbyshire, Yorkshire, &c.; and a few species occur in the Coralline Oolite; their general configuration will be understood by the figureLign.70,fig.3; but in this specimen the margins of the cells are worn off, and do not present the original deeply excavated form.[249]

[249]Lithodendron fasciculatum, Pict. Atlas, pl. xxxviii.

There is a remarkable specimen of this coral in the Bristol Institution (of which a portion is now placed in the Museum of Practical Geology, in London), that was discovered by Mr. Samuel Stutchbury,[250]in a vein of hematitic iron ore. It is a large mass, in which the entire substance of the coral is transmuted into a metallic ore, forming one of the most interesting natural electrotypes I have ever seen. In this instance, a block of Lithodendron must have lain in a vein or fissure of the rock, and its animal membrane have resisted the action of the gaseous emanations, or mineral solutions, while the calcareous polypidom was dissolved, and the metallic matter deposited atom by atom, as in the case of pseudo-morphous crystals.

[250]Now of Sydney, Australia.

Gorgonia.—Of the flexible anthozoan coral, which from the flabellated form of the polyparium is generally called "Venus's fan," and by naturalistsGorgonia, a few fossil species have been discovered and determined. From the friable arenaceous limestone beds of Maestricht, which abound in corals, fine specimens of a delicate species are occasionally procured.Wond.p. 320,fig.5, shows the character of this fossil zoophyte.

Fossil Bryozoa.

FOSSIL BRYOZOA.

The second class of Polypifera, theBryozoaorPolyzoa, are of a much higher order of organization than those which have engaged our attention. The body is not symmetrical,nor capable of contraction and expansion, as in the Anthozoa: it consists of a digestive cavity or sac, which is bent on itself and open at both extremities. The outer integument is either membranaceous or horny; sometimes calcareous. The oral aperture or mouth is surrounded by a circle of tentacula, from eight to twelve or more in number, and these tentacles are clothed with vibratile cilia. (Wond.p. 606, the polype ofFlustra pilosa.)

The polypes in this order never occur singly; they are always united by a common integument, but each enjoys an individual existence. The animal can extend its tentacula and protrude the mouth from the cell, but the rest of the body is incapable of extension or contraction. These polypifera increase by germination. In their organization, they so closely approach the mollusca, that in recent zoological systems they are placed in that class. The ciliated character of their tentacula has also led to their being namedCilio-branchiata. But as it is desirable in a work of this elementary nature to avoid conflicting opinions as much as possible, the fossil Bryozoa will be considered as corals, in the general sense of that term.

FLUSTRA. ESCHARA.

Flustra(Sea-mat).Lign.89,fig.4, 5.—The polyparium is either membranaceous and flexible, calcareous and encrusting, or foliaceous, composed of cells, arranged in juxtaposition, more or less quadrangular, flat, with a distinct border, disposed on a flat surface, or on opposite surfaces, as in theF. foliacea.

This is one of the most common genera of the encrusting and frondescent zoophytes. TheFlustraconsists of a cluster, or aggregation of polypes, invisible to the naked eye; under the microscope, the polype is found to be a transparent gelatinous body bent on itself, with a sac or digestive cavity, having two apertures, the external margin of which terminates in eight or ten tentacula, clothed with cilia; the whole is surrounded by a firm wall, constituting a cell, fromwhich the animal can protrude its tentacula and upper part. (Figures of the living polypes of Flustræ,Wond.p. 605,pl.vi.fig.6, 7.)

Many species ofFlustræoccur in the British strata: the encrusting forms are attached to echinites, shells, &c.; the foliaceous are imbedded in chalk, sand, sandstone, &c. In Mr. Morris'sCat. Brit. Foss.ten species are enumerated; none of these are from formations below the Chalk. I have selected for illustration a Flustra attached to an echinite from Lewes.Lign.89,fig.5, represents a small portion of the natural size; andfig.4, a few cells magnified, to show their form and arrangement. A foliaceous zoophyte, apparently a bryozoon, is abundant in the Sussex and Kentish chalk, and is often disposed in angular folds. It is generally of a ferruginous colour, and, from its friable texture, it is probable the original consisted of a membranous polypidom or calcareous substance; specimens sometimes extend over several square inches of the chalk. It is common in the chalk-pit at Off ham, near Lewes.[251]

[251]In my South Down Fossils, pl. xv.fig.6, a specimen of this kind is described as a Ventriculite,V. quadrangularis. An admirable lignograph of a remarkable example is given by Mr. Toulmin Smith, under the name ofBrachiolites angularis; it presents ten deep, flat, angular folds, and has radicle and lateral processes; see "On the Ventriculidæ," p. 93.

Eschara.[252]—In these zoophytes the polyparium is encrusting or foliaceous, calcareous and brittle; the cells are thickened on their outer margins, and have a small, depressed, round aperture. They are arranged in two series of planes, adhering together, the cells on each surface exactly corresponding.

[252]So named from a supposed resemblance to an eschar.

Species of Escharæ are found either in flints, or attached to echinites, and other bodies; they have the appearance of patches of flustræ, but with a lens may be distinguished by the symmetrical juxtaposition of the cells on the opposite sides of the polyparium.

Ellen Maria Mantell, ad nat. delt.Lign. 89. Corals from the Chalk and Mountain Limestone.Fig.1.—Carophyllia centralis;nat.(G. A. M.)Cret. Lewes.2.—Front view of half the disc of the same.3.—Two cells ofCrisia Johnstoniana. × ×.4.—Magnified view of six cells of the Flustra,fig.5.5.—A portion of an encrusting Flustra;nat.Cret. Chichester.6.—Idmonea (Dixoniana) cretacea;nat.Cret. Lewes.The figure on the left shows the under surface; that on theright, the upper surface, with a row of polype-cells oneach margin: a portion magnified is givenfig.12.7.—Millepora rhombifera.× ×.Mt. L. Ph. Yorks.The small figure on the left is of the natural size.8.—Pustulopora pustulosa.× ×.Cret. Chichester.The small figure on the left,nat.9.—Homœsolen ramulosus.× ×.Cret. Dover.The left-hand figure,nat.10.—Crisia (?) Johnstoniana.(G. A. M.) × 250 linear.S. s. Maidstone.10b.—Two cells of the coral,fig.10, seen in profile, × ×.11.—Homœsolen ramulosus;nat.Cret. Lewes.12.—Idmonea Dixoniana; a portion offig.6. ×.13.—Retepora laxa.Mt. L. Ph. Yorks.13†.—A portion of the same ×.14.—Idmonea Comptoniana. × ×. (G. A. M.)Chalk, Chichester.(Mr. Walter Mantell.)The small figure on the right is of the natural size.

MICROSCOPIC FOSSIL BRYOZOA.

Crisia Johnstoniana.Lign.89,fig.3, 10, 10b.—The minute recent corals thus designated are allied toFlustra, but separated from that genus by the cells being disposed in a single series, and united by connecting tubes. I notice this genus to direct attention to a very curious polypidom from the Greensand of Maidstone, presented to me by Mr. Bensted. The specimen is attached to a fragment of shell. The cells, five of which are represented,fig.10, are elliptical, with the aperture above, and towards one extremity; they are united by very slender, hollow filaments:fig.3, two of the cells seen from above × 250 linear;fig.10bthe same seen in profile.[253]I have named this speciesC. Johnstoniana, as a tribute of respect to the author of the admirable works on British Zoophytes, previously noticed.

[253]I refer this fossil to the genusCrisiawith some hesitation; perhapsHippathoeawould be more correct, but all the described species of the latter are branched.

The fragmentary relics of numerous minute and elegant corals, constitute a considerable portion of the mass of some of the white chalk strata; several genera of these zoophytes are figured in Mr. Dixon's beautiful work, and described by Mr. Lonsdale. Attached to the surface of shells, &c., and sometimes standing erect in little crannies, or hollows, of the flints, many beautiful corals may often be detected with the aid of a lens. By brushing chalk in cold water, and examining the deposit, the student will probably discover several of the species figured inLign.89, which we proceed to describe.

Retepora(Lace-Coral).Lign.89,fig.13.—A very thin calcareous polyparium, disposed like net-work in foliaceous and branching plates; cells opening either on the upper or inner side.

These are an elegant tribe of corals, of which many species occur in the Chalk formation at Maestricht, in the white-chalk of England, in the mountain limestone of Yorkshire,(Phil. York.), and in the Silurian deposits (Sil. Syst.). It may be useful to state, that in the description of the fossil retepores, the openings in the net-work are called fenestrules—the spaces between the ends,dissepiments—and those between the fenestrules, interstices. A delicate fossil retepore from the mountain limestone of Yorkshire (R. flexa), is figuredLign.89,fig.13.

Fenestrella.—Cells very small, indistinct externally, with small prominent openings; polyparium stony, fixed at the base, composed of branches, which inosculate by growth, and form a cup. Numerous delicate corals, formerly arranged asReteporæ, occur in the Silurian rocks, and have been placed in this genus by Mr. Lonsdale. (Sil. Syst.p. 677.)

Petalæpora pulchella.[254]Lign.69,fig.1.—This beautiful cretaceous coral is "tubular, free except at the base; framework composed of vertical laminæ, with an intermediate foraminated structure; apertures to the tubular cavities distributed over the surface; exterior varying with age." It has slender round dichotomous branches, and the polyparium when entire must have formed an elegant plexus of coral. A layer an inch thick, full of branches of this zoophyte, is exposed on the face of the chalk cliffs, near Dover; and beautiful masses, several inches square, made up of this coral, Idmonea and Pustulopora, may be obtained. The microscopic specimen figured inLign.69, was obtained with many other corals by washing chalk with a brush, and examining the detritus deposited.

[254]Mr. Lonsdale. Dixon's Fossils, p. 285.

Pustulopora.Lign.89,fig.8.—Another very common tubular branched coral of the Dover chalk; the tubes are cylindrical, their apertures are arranged in annular or spiral rows, and slightly projecting, giving a pustulous appearance to the stem and branches. Specimens covering a piece of chalk six or eight inches wide, and a foot long, have been discovered. The example figured is a very minute branch.

Homœsolen ramulosus.[255]Lign.89,figs.9, 11.—This delicate branched coral is formed of large and small tubes variously intermingled, both inclined in the same direction, partially visible on the surface, or wholly concealed, limited to one side of the coral; mouths simple tubular extremities; back without pores, composed of a continuous lamina.[256]

[255]Homœsolen, from ομοιος, similar; and σωλην, a tube.[256]Mr. Lonsdale, in Dixon's Fossils, p. 307, tab. xviii. B. figs, 3, 4, 5.

[255]Homœsolen, from ομοιος, similar; and σωλην, a tube.

[256]Mr. Lonsdale, in Dixon's Fossils, p. 307, tab. xviii. B. figs, 3, 4, 5.

The elegant coral,fig.11,Lign.89, is thus named by Mr. Lonsdale; it resembles hisfig.4. The fossil,fig.9,Lign.89, though very different in its branching, and in the surface, which is covered with pores, is evidently identical withfig.3 of Mr. Lonsdale, which he refers to the same species.

Idmonea,Lign.89,fig.6.—In this elegant coral the polyparium is calcareous, branched, porous; the cells distinct, prominent, arranged in single rows, more or less inclined, on each side a median line on the inner face only. The genus is extinct.

A beautiful species of Idmonea, of which a small branch is figured inLign.89, abounds in the chalk of Kent and Sussex; it often forms a cluster, two or three inches in circumference. The surface of the stems is covered with minute pores, and the cells are distinct, and placed in single rows; the left-hand figure offig.6 shows the plain surface, and that on the right, the opposite and inner, each margin of which is garnished with a row of cells; a portion magnified is representedfig.12.[257]

[257]In the former edition of this work, I named this speciesI. Dixoniana, to commemorate the researches of my late friend, Frederic Dixon, Esq., of Worthing, who had formed an interesting collection of chalk fossils, and announced a work on the "Zoology of the Chalk Formation," to be richly illustrated with figures of many undescribed organic remains. It appears that a species, supposed to be identical, had been previously named by Mr. Milne Edwards,I. cretacea. See Dixon's Foss. tab. xviii. A.fig.5, p. 281. Mr. Lonsdale places it in a new genus, with the name of Desmeopora semicylindrica. It will convey some idea to the unscientific reader, of the labour bestowed on this department of palæontology, to learn that the description and identification of but 25 species of minute corals, represented on three plates, occupy ninety pages of close printing in royal 4to. of Mr. Dixon's work.

Idmonea Comptoniana,[258]Lign.89,fig.14.—This is a very small and remarkable coral; it is dichotomous, cylindrical, with elongated distinct cells, which are disposed in triplets, at regular distinct intervals, on one side of the stem.

[258]This specific name is in honour of the noble and highly respected President of the Royal Society, the Marquess of Northampton. 1844.

We have now described all the fossil corals figured inLign.89; and have shown what interesting organisms may be detected in a few grains of calcareous earth. It would be easy to give restored figures of the beings whose stony skeletons are the subject of these remarks, from their close resemblance to existing species; every pore and cell might be represented fraught with life; here the agile inmates, with their little arms fully expanded, and in rapid motion; there retreating within their recesses, and devouring the infinitesimal living atoms that constitute their food; or rapidly shrinking up their tentacula upon the approach of danger; even their varied colours might be introduced, and thus the beautiful and highly interesting picture drawn by the imagination, of a group of living zoophytes of the ancient chalk ocean, be presented to the eye.

Although, for convenience, I have selected the above examples principally from the cretaceous strata, the reader must not suppose that other deposits are not equally prolific in these remains. The Coral-rag of the Oolite, many beds of the Mountain limestone, and those of Dudley and Wenlock of the Silurian System, contain myriads of minute polypidoms associated with the coralline masses of which we have already treated. Exquisite figures of the Silurian corals, by Mr. Scharf, are given inSil. Syst.pl. xv. xvi. and described byMr. Lonsdale. A slab of the Dudley limestone often has the entire surface studded with minute corals of many species and genera, lying in bold relief, and in an admirable state of preservation.

Verticillipora(Lign.70,fig.4.Lign.72,fig.3).—Cells poriform, arranged in meshes on the surface of convex imbricating plates round a hollow axis, forming a fixed, irregular, subcylindrical polyparium.Lign.70,fig.4, represents a coral often met with in the gravel-pits at Faringdon, (ante,p. 228.,) which is referred by Mr, Morris to this genus. It is composed of short cylindrical anastomosing tubular branches, emanating from an expanded base, divided internally by transverse parallel plates, covered with exceedingly minute pores or cells, disposed in meshes; the plates surround a hollow axis; the structure is well shown in the figure.

Lunulites.Lign.70.—The polyparium is stony, orbicular, convex above, concave below; concavity radiated; convexity covered with cells, arranged in concentric circles on diverging striæ.

A species of this coral is often found in the chalk:Lign.70,fig.1, represents a specimen from the South Downs, discovered by Mr. Walter Mantell. The natural affinities of this genus are not determined with precision; but I have placed it with the Bryozoa in accordance with the opinion of M. de Blainville. It is an elegant white coral, and easily recognized among the minute organisms of the chalk.

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