CHAPTER VIII.

DISTRIBUTION OF FOSSIL BRYOZOA.

Geological Distribution of Fossil Zoophytes.—Although the geological distribution of fossil zoophytes affords less striking phenomena than that of the vegetable kingdom, yet some interesting reflections are suggested by the facts we have thus cursorily noticed. We find that in the most ancient seas of which any vestiges of their inhabitants remain, these forms of vitality existed, and produced the same physical results as at the present time; giving rise to coral-reefs,and banks of coral-limestones, and largely contributing to the solid materials of the crust of the globe. Nearly 400 British species are enumerated by Mr. Morris, and the list has subsequently been greatly extended by the labours of Phillips, Portlock, Lonsdale, McCoy, Milne Edwards, and other eminent naturalists.

The Tertiary formations afford numerous species of Caryophylliæ, Flustræ, Escharæ, Spongia, &c.; and theCrag, several genera that are as yet but imperfectly determined. The older Tertiary, or Eocene deposits, contain Turbinoliæ, Astreæ, Fungiæ, Meandrinæ, and species of other genera, the recent types of which are inhabitants of tropical seas.

The zoophytes of the British Chalk have been illustrated in detail by Mr. Lonsdale in Dixon's Cretaceous and Tertiary Fossils of the South-East of England; and by Dr. Milne Edwards in the Monographs of the Palæontological Society.

In the Maestricht deposits, lamelliferous corals, as Astreæ, Fungiæ, Meandrinæ, &c. prevail, and may be extracted from the friable arenaceous limestones in a fine state of preservation. In the White Chalk and Greensand of this country, the Spongites and allied genera are abundant, and associated with Caryophylliæ, Astreæ, and many forms of Bryozoa.

But in the cretaceous formation of England, no coral-reefs are observable; the zoophytal remains, with but a few local exceptions, occur promiscuously intermingled with the fishes, shells, Radiaria, and other marine exuviæ; although many layers, or thin seams of chalk and marl, are largely composed of the detritus of corals, like the modern deposits of the Bermudas (Wond.p. 613). These phenomena are in accordance with the lithological characters of the White Chalk strata, and the nature of its mollusca, both of which indicate a deep sea; and coral-reefs are only formed at moderatedepths. But in regions where the sea was shallow, during the deposition of the cretaceous rocks, beds of coral limestone were produced; and these also contain littoral (sea-shore) shells, associated with the usual sponges and zoophytes (Wond.p. 613).

In the marine secondary formations antecedent to the cretaceous, namely, the Lias and Oolite, coral-reefs, which appear to have undergone no change save that of elevation from the bottom of the sea, and the consolidation of their materials by mineral infiltrations, demonstrate a condition of the ocean in our latitudes, which is now only met with in the tropics (Wond.p. 614).

The limestones of the Carboniferous, Devonian, and Silurian formations, abound in anthozoan corals, and among them are many kinds of Cyathophyllum, Lithododendra, Syringopora, Catenipora, Graptolites, &c., which are characteristic of these deposits.

The Silurian zoophytes are figured inSil. Syst.; and the splendid works on the British Palæozoic Fossils, by Prof. Sedgwick and Prof. McCoy, now in course of publication, contain many admirable figures of new, or but imperfectly known species.

The extensive beds of coralline limestones, which are found in the Silurian strata, wherever they occur,—for the limestones of this system in North America are characterized by the same species of corals as those of England,—seem to indicate that a more equal temperature prevailed throughout the ocean, at that geological epoch, than at the present time, when the geographical distribution of the coral zoophytes is strictly limited by temperature. The reef-forming genera are now confined to waters where the temperature is not below 70°; their most prolific development being 76°. The apparent exception, the occurrence of coral-reefs at the Bermudas, is found to depend upon proximity to the Gulf Stream (Wond.p. 614), which brings down the thermal waters ofthe tropics, and increases the local temperature of the sea in those localities.[259]

[259]Mr. Deane's splendid and masterly work on Corals, should be studied by those who wish to be acquainted with the present state of this branch of natural history.

ON COLLECTING FOSSIL CORALS.

On Collecting Fossil Corals.—Few instructions are required for the collection of fossil zoophytes; for as the most important characters of the several kinds have been pointed out in the previous descriptions, the student will be able to select illustrative specimens for his cabinet. The minute corals, &c. of the Chalk, and other limestones, are to be obtained by the same process as that directed for the discovery and preservation of the foraminifera, and other microscopic organisms, at the end of the next chapter. The larger examples should be left attached to a piece of chalk, when practicable, and the surrounding stone removed with a knife or graver, so as to expose as much of the fossil as may be required for the display of its characters, without loosening its attachment to the block. When the investing chalk is very hard, frequently pencilling the specimen with vinegar, or dilute hydrochloric acid, will soften the stone, and render its removal easy, by means of a soft brush: when acid is employed, the specimen must afterwards be well rinsed in cold water.[260]

[260]It may be well to caution the collector against employing sulphuric acid (commonly calledoilofvitriol) for this purpose, for a white insoluble deposit (sulphate of lime) will thus be formed on the specimen, and its appearance irremediably injured. Many of the fossil corals obtained from the chalk of Dover Cliffs, are so saturated with muriate of soda, from long exposure to the spray of the sea, as to be liable to decomposition in the course of a few weeks, and are therefore not worth purchasing of the dealers.

The zoophytes that are in part flint, and part chalk, as the Ventriculites, (ante,p. 244,Lign.81,) can rarely be obtained, except through the quarrymen who have been instructed how to extract them from the rock. The firstspecimen of this kind that came under my notice, I discovered while breaking a mass of chalk, in search of fungiform flints; when, to my great delight, I found the fossil,Lign.81,fig.3, by which at once, and for the first time, was shown the connexion between the chalk specimens,Lign.8,figs.1, 2, and the flints figured inLign.8,figs.2, 3, 6, 7, 8. Upon showing this fossil to the quarrymen, and exciting their attention by suitable rewards, I obtained the illustrative series now in the British Museum.[261]Much light would be thrown on the nature of other zoophytes of the chalk that are invested with flint, if due care were taken in the collection of specimens, and they were examined before extracted from the rock. Loose, delicate specimens, whether from the chalk or tertiary strata, should be affixed with strong gum-water to cards, or pieces of thin board, covered with coloured paper.

[261]Petrifactions, Room VI. p. 466.

The Greensand Spongites, Siphoniæ, &c. may often be extracted from the rock tolerably perfect, by a well-directed blow of the hammer; but fragile species should be left attached to a block, and the surrounding stone be carefully chiselled away, so as to expose the most essential characters.

The Faringdon zoophytes are, for the most part, encrusted by an aggregation of minute polyparia, shells, and detritus, which may be partially removed by washing with a stiff brush, and their cavities cleared with a stout penknife, removing the extraneous matter bychipping, not by scraping, or the surface will be injured. In this manner the beautiful specimens figured,ante,p. 228., were developed.

The Corals in the hard limestones can seldom be chiselled out to advantage; for the most part, polished sections best exhibit the form and structure of the originals.

Weather-worn or water-worn masses of coral limestone often display the structure of the zoophytes of which they are in a great measure composed, in a beautiful state ofsculpture and relief: the silicified or calcified corals appearing as perfect as if fresh from the sea. The mural rocks of coral limestone at Florence Court, the seat of the Earl of Enniskillen, are in many parts encrusted, as it were, with syringopora and other tubular corals, laid bare uninjured by the long and insensible effect of atmospheric erosion. A beautiful illustration of the old aphorism,—"Aqua cavat lapidem non vi sed sæpe cadendo,"—is afforded by the splendid examples of cateniporæ, fungiæ, caryophillæ, sculptured in alto-relievo on the face of the Silurian rocks over which dash the rapids at the Falls of the Ohio.

The silicified zoophytes of the West Indies, and those from Ava and the Sub-Himalayas, form beautiful subjects for the microscope; and chips, or sections, should be prepared in the manner recommended for fossil wood in the same state of mineralization.

LOCALITIES OF FOSSIL ZOOPHYTES.

British localities.—The gravels and sands of the Crag afford most favourable sites for obtaining tertiary zoophytes.

In the London clay at Bracklesham Bay, a species of Astrea (A. Websteri) is often met with attached to flints and pebbles.

In the Greensand of Atherfield, in the Isle of Wight, an elegant coral (Astrea elegans) is by no means rare.

The Greensand gravel-pits, near Faringdon, in Berkshire, abound, as already mentioned, (ante,p. 228.,) in many kinds of sponges, and other porifera; and the quarries of oolitic limestone in the vicinity of that town, yield the usual corals of the Jurassic formation in great profusion, I know of no locality richer in fossil zoophytes, than Faringdon.[262]

[262]See Excursion, Part IV. of this work.

The quarries of that division of the Oolite called Coral-rag (as in the north-west of Berkshire, Oxfordshire, Gloucestershire, &c.), afford the usual corals of the Oolite.

The Oolite near Bath contains many species, and large masses of a minute coral (Eunomia radiata), are abundant.

At Steeple Ashton, in Wiltshire, numerous oolitic corals may be obtained. The silicifiedAstreæ, of Tisbury, in the same county, deserve particular notice (ante,p. 263).

Clifton, near Bristol, and Torquay and Babbicombe, on the Devonshire coast, are celebrated for their coralline marbles and pebbles; and many of the Derbyshire limestones are equally prolific in similar remains. The Devonian marbles are so largely employed for ornamental purposes,— as brooches, tables, and side-boards,—that the figures produced by the sections of the enclosed corals must be familiar to the reader.[263]

[263]Specimens of these fossil corals, either as objects of natural history, or as ornaments, may be obtained of Mr. Tennant, 149, Strand.

Dudley, Wenlock, and Ludlow, are well known for the abundance and variety of Silurian polyparia.

Other localities of British corals have been mentioned in the course of this review of fossil zoophytes.

FOSSIL STELLERIDÆ; COMPRISING THE CRINOIDEA OR LILY-LIKE ANIMALS; AND THE ASTERIADÆ, OR STAR-FISHES.

The Radiata, or radiated animals, so designated because the parts of which the body is composed are arranged around a common centre or axis, are divided into three sub-classes; namely, 1, thePolypifera, whose fossil remains were treated of in the previous chapter; 2. theAcalepha, or Jelly-fishes, whose structures are so perishable as to render it improbable that any vestiges of them will be found in a fossil state, though imprints of the general outline of certain kinds may possibly occur;[264]and, 3, theEchinodermata, comprehending under that term theStelleridæ, or Crinoids and Star-fishes, and theEchinoderms, properly so called. This sub-class is the subject of the present section; it comprises four orders, viz.

[264]The impression of an Acaleph resembling anÆquorea(a kind of Medusa), is stated by M. Pictet to have been observed in a slab of schistose rock, in Germany.

Vestiges of the Stellerida are among the earliest relics of animal organization hitherto discovered. Many kinds of Crinoidea abound in the Silurian rocks, and one genus of Star-fishes occurs in the same deposits: the Echinidæ first appear in the Devonian formation.

The Echinodermata possess the radiated type of structure in an eminent degree; especially the Asterioidæ and the Echinidæ, of which the common Star-fish, and Sea-urchin, are familiar examples. The external integument or skin is in many kinds protected by spines, (hence the name Echinoderms or spiny-skin,) and perforated by numerous foramina for the imbibition and transmission of sea-water, and for the protection of minute soft tubular processes (calledpseudopodia), which constitute organs of adhesion and locomotion.

The first two orders have endo-skeletons, composed of numerous ossicula or little calcareous bones: in the third order, the Echinidæ, the body is inclosed in a calcareous case or shell, formed of numerous plates closely adjusted to each other; in the fourth order, the Sea-slugs, the body has only a tough outer integument without movable spines.

Diversified in form and external appearance as are the Invertebrata thus grouped together, they are naturally related by their organization. The Crinoidea may be regarded as Star-fishes fixed to one spot by a jointed stem; the Star-fishes as free Crinoidea; the Echinidæ as Star-fishes with the rays coalesced and united into a globular or spherical case; and the Holothuriæ, as elongated Sea-urchins, destitute of spines, and without a calcareous envelop.

CRINOIDEA.

Crinoidea.—The animals of this order are subdivided into families and genera according to the number, form, and arrangement of the plates composing the calcareous case or receptacle, and the structure of the arms and column. In one living family, theComatulidæ, the body is free; and in one fossil genus, theMarsupite, the animal is capable of locomotion through the water.

The essential character of theCrinoidea,[265]—so namedbecause the receptacle and anus of some kinds resemble when in repose a closed lily or tulip,—are well exemplified in the recentPentacrinus; the only known living form that is identical in structure with the numerous extinct tribes, that swarmed in the seas of the palæozoic and secondary ages.

[265]From κρινον,crinon, lily, and ειδος,eidos, a form.

ThePentacrinus(F. caput-medusæ,Wond.p. 647), is an inhabitant of the Caribbean Sea, and but rarely obtained; there are specimens in the British Museum[266]and in the Hunterian Collection of the College of Surgeons.

[266]Petrifactions, p. 77.

This animal has a long stem or column, which is composed of pentagonal calcareous plates or ossicula, articulated to each other by radiated surfaces, and is fixed by the base to a rock, or other firm body. The column supports a vasiform receptacle or cup, formed of calcareous plates in close apposition; in which the digestive and other viscera are situated. The upper part of the receptacle is covered by an integument in which there is an aperture for the mouth. From the margin or brim proceed ten multi-radiate arms, which subdivide into branches of extreme tenuity. On the upper and inner side of the arms are numerous articulated feelers or pinnæ. The ova are situated externally on and near the base of the arms, as in the Comatulidæ; a family of living Star-fishes, or more properly Crinoids, which have a receptacle, surrounded by articulated and multi-radiate arms, but are free animals, being destitute of a column.

In the living state of Pentacrinus, the skeleton—for such are the specimens in our museums—was of course covered and concealed by the soft integuments and tissues by which it was secreted. The ossicula composing the stem are pentangular, and very numerous; they have a central perforation, and their articulating surfaces are ornamented bypentapetalous striations. There are numerous side-arms sent off from the column in groups of five, at uncertain distances. The mouth is situated in the centre of a plated integument spread over the top of the receptacle. The arms, which arise from the margin of the latter, surround the mouth, and when spread out, with their numerous pinnæ or feelers expanded, form a net for the capture of prey; and are the organs by which the animal obtains food, and conveys it to the mouth.

FOSSIL CRINOIDEA.

Fossil Crinoidea.—The fossil crinoids, like the recent prototype above described, consist of an articulated column, and a receptacle formed of calcareous plates, and articulated arms or tentacula. They constitute two groups; theEncrinites, in which the ossicula of the column are subcylindrical and smooth; and thePentacrinites, with a stem composed of pentangular ossicles, as in the living Pentacrinus.

The petrified remains consist of the ossicula of the column, arms, and tentacula; of the plates of the receptacle; and of the peduncle, or process of attachment by which the animal was fixed to the rock. The peduncle is in some species flat and expanded, like that of theGorgonia; in others, it consists of long jointed processes. These several parts are commonly found detached, and intermingled with detritus in the strata; throughout extensive beds of encrinital marble, vestiges of the receptacle are but seldom discoverable. In some localities the skeletons are preserved entire, and lie expanded on the surface of the layers of shale, clay, or limestone, as if the animals had been enveloped by the soft deposit when alive in their native seas.

These remarks will serve to convey a general idea of the nature of the crinoidal remains which are scattered through certain rocks in such inconceivable quantities; for, much as the columns may differ in form, the ossicula in their markings, and the plates of the receptacle in their configurationand ornament, the same general type of structure prevails throughout the family.

Lign. 90. Stems of Encrinites and Pentacrinites.Fig.1.—Screw or Pulley-stone.Derbyshire.2, 4.—Articulating surfaces of Encrinital ossicula.3, 5.—Entrochites, or portions of stems of Encrinites.6, 8, 10.—Portions of Pentacrinital stems.7, 9.—Articulating surfaces of ossicula of Pentacrinites.

Fossil Stems and Ossicula of Crinoidea.—(Bd.pl. xlix-lii.Pict. Atlas, pl. xlvii.)—The detached ossicula and stems are so common in many places, that they attracted the notice of the earlier collectors, by whom the single pieces were termedtrochites(wheel-stones), and the united seriesentrochites. In the north of England these fossils are calledFairy-stones, and the circular perforated ossiculaSaint Cuthbert's beads; the latter were worn as ornaments by the ancient Britons, and are occasionally found in tumuli.

These petrifactions present considerable variety in form, and in the markings on their articulating surfaces, whichare often radiated and sculptured in floriform and stellular figures (Lign.90,fig.7, 9, andLign.91,fig.3, 4). The central perforation is small in some species, and large and pentagonal in others. The ossicula of the Encrinites often vary in size in the same column, being circular and elliptical, and thick or thin, alternately, as in the upper part of the column of the Lily Encrinite,Lign.91,fig.6; by which great flexibility and freedom of motion were obtained.

The pentagonal stems also display many modifications; some have five, others but four sides (Lign.90,fig.6, 8, 10, and 91,fig.7, 9); in some the angles are acute, in others rounded.

Pulley-stones.Lign.90,fig.1.—The circular, or pentagonal channel formed by the united ossicula of the column, has given rise to the curious fossils called in Derbyshire the Screw, or Pulley-stones, which are flint casts of those cavities that occur in the beds of chert, interstratified with the mountain limestone. The siliceous matter, when fluid, must have filled up the channel and invested the stem: the original calcareous ossicles have since been dissolved, and the casts, now solid cylinders of flint, resembling a pulley, remain. The masses of chert are often impressed with the ornamented articulating surfaces of the trochites.

In the quarries on Middleton Moor, near Cromford, Derbyshire, where extensive beds of limestone composed of crinoideal remains are worked for chimney-pieces and other ornamental purposes, beautiful examples of these fossils may be obtained.[267]The cavities of the column and ossicles are often filled with white calcareous spar, while the ground of the marble is of a dark reddish brown colour; in other varieties of the Derbyshire encrinital limestones, the substance of the fossils is white, and the ground dark grey or brown,[268]A slab of this marble, with portions of columns lying in relief, and a polished section showing the inclosed entrochites, are figuredWond.p. 650.[269]

[267]See Excursions around Matlock, Part IV. of this work.[268]Pict. Atlas, pl. xlix. figs. 1, 3, 6.[269]Upwards of 80 figures of Encrinital remains are given in Pict. Atlas, pl. xlvii.

[267]See Excursions around Matlock, Part IV. of this work.

[268]Pict. Atlas, pl. xlix. figs. 1, 3, 6.

[269]Upwards of 80 figures of Encrinital remains are given in Pict. Atlas, pl. xlvii.

Lign. 91. Illustrations of Crinoidea.Fig.1.—Group of LivingComatulæ;nat.(Dr. Thompson.)1a.—A singleComatulaof the same group, magnified.2.—Pentremites pyriformis.Silurian, Ohio.3, 4.—Surfaces of two pentapetalous ossicula.5.—A single Ossicle of anApiocrinus.Chalk.6.—Encrinus liliiformis; the receptacle with part of thecolumn attached;1/2nat.From Brunswick.7.—Pentacrinitalstem with four angles.8.—Entrochite, composed of five smooth ossicles.9.—Quadrangular stem of seven ossicles.10.—Cyathocrinus tuberculatus.(Sil. Syst.)11.—Receptacle ofBourqueticrinus;from the Chalk. Lewes.

Thereceptaclewhich contained the viscera is extremely diversified in form, and in the number, shape, and arrangement of its plates: the annexed figure 2,Lign.92, illustrates the several pieces that enter into its composition. The genera, or sub-genera, are based on the modifications of shape and structure of the receptacle; and their names are composed of the terminationcrinus, orcrinites(signifying stone-lily), with a term prefixed expressive of the generic character: thus we haveApiocrinus, orApiocrinites, Pear Encrinite.[270]

[270]The terminationcrinusis now generally employed, instead ofcrinites; the latter is preferable, as it indicates the fossil nature of the specimens. A more expressive name thanEncrinitewas suggested by Mr. Martin, of Derbyshire; that ofStylastritæor Column-Stars.

The receptacle being round and inflated, and composed of pieces articulated with the stems, and supporting the arms by similar articulations, are the generic characters ofApiocrinitesof Miller. When round but not inflated—Encrinus, when pentagonal,Pentacrinus. When the receptacle is composed of angular plates united at the edges and forming several series or stages, it constitutes the basis of the following genera: viz,—

Platycrinus; two series, the one of three, the other of five plates.

Pateriocrinus; three series each of five plates.

Cyathocrinus; three series of five plates, the last with five intercalated pieces.

Actinocrinus; several series of plates: the first composed of three, the second of five, and the others of many pieces.

Rhodocrinus; several series of plates that are covered externally with radiated ridges. The first course consists ofthree, the second of five, the third of ten, and the others of many plates.

Eugeniacrinus; of five pieces united into one receptacle.

This brief explanation will enable the student to comprehend the nature of the almost infinite variety of figure and ornament which the fossil crinoidea present, and the principles of nomenclature generally adopted by modern authors. To attempt an enumeration even of the genera would be inadmissible in these volumes. The late Mr. Miller's "Natural History of the Crinoidea or Lily-shaped Animals,"[271]will afford the student satisfactory information on this class of organic remains.[272]

[271]Published in 1 vol. 4to. 1821, with coloured plates.[272]A beautiful "Monograph on the Recent and Fossil Crinoidea," by Messrs. Austin, in 4to. is in course of publication, of which but eight numbers have appeared.

[271]Published in 1 vol. 4to. 1821, with coloured plates.

[272]A beautiful "Monograph on the Recent and Fossil Crinoidea," by Messrs. Austin, in 4to. is in course of publication, of which but eight numbers have appeared.

Apiocrinus(A. Parkinsoni).Lign.92,fig.4. (Wond.. p. 652.)—The Apiocrinite or Pear-Encrinite of Bradford, from its size, and the abundance of its remains in one particular locality, is the most generally known of all the British fossil Crinoids. It abounds in the beds of oolite, in the quarries on the heights above the picturesquely situated town of Bradford, in Wiltshire. The receptacle, detached ossicula, and the pedicle, are very common; and in some instances the entire endo-skeleton, from the peduncle to the extremities of the arms, is preserved. The late Channing Pearce, Esq., of Bradford, by unremitting attention to the collection of these fossils, obtained the beautiful specimens deposited in the British Museum.[273]

[273]Petrifactions, Room II. Wall-case G.

This Apiocrinite has a smooth receptacle of a pyriform shape, composed of large thin plates with radiated articulating surfaces; the stem is short and strong; the arms are simple, resembling those of theMarsupite; the peduncle spreads outinto an expanded base, which is firmly attached to the rock, like that of the Gorgonia, and is generally of a rich purple colour.[274]

[274]Pictorial Atlas, pl. xlix. Pulley-stones and Encrinital marbles; pl. 1. Apiocrinites.

Lign. 92. Fossil Crinoidea.Fig.1.—Eugeniacrinus.Switzerland.2.—Cyathocrinus planus.Mountain Limestone.a.Basal plate of thereceptacle.b.One of the plates composing the walls of the pelvis.c.Costal plate.d.Intercostal plate.e.Scapula, or ossicle that receives the arm.f.First ossicle of the arm.3.—Marsupites Milleri(G. A. M.).Chalk, Brighton.a.The semilunar cavity for an attachment of the arm.4.—Apiocrinus rotundus,Pear-Encrinite. Bradford.a.First ossicles of the arms.

Sir Charles Lyell mentions an interesting fact relating to the occurrence of these fossils in the Oolitic limestone at Bradford. In Burfield quarry, on the heights that overlookthe town, a bed of limestone was exposed, the upper surface of which was incrusted with the stony peduncles or roots of Apiocrinites; upon this stratum was a layer of clay, in which were innumerable remains of receptacles and ossicula of stems and arms; some of the stems were erect, others prostrate, and throughout the clay were the dismembered remains. This submarine forest of Crinoideans must therefore have flourished in the clear sea-water, till invaded by a current loaded with mud that overwhelmed the living zoophytes, and entombed them in the argillaceous deposit in which their fossil remains are imbedded.[275]

[275]Burfield quarry, on the heights of Bradford, is the locality referred to; but I believe it is rarely that any specimens of the Apiocrinite are to be found in an erect position. I could not learn from any of the local collectors, that an example had been seen by them. When I visited the quarry in June, 1848, no good section of the beds was apparent: a few detached plates of Apiocrinites were the only relics we could meet with. Mr. Reginald Mantell, when engaged on the construction of the railway near Bradford, sought repeatedly, but in vain, to discover any Apiocrinites in an erect position, or as if lying on the spot where they grew.

The constituent substance of the ossicula and plates of the Bradford Encrinite is calcareous, and has an oblique fracture; the colour is generally a light ochre, or a bluish grey.[276]

[276]Pict. Atlas, pl. 1. contains figures of the Bradford Encrinites.

APIOCRINITE OF THE CHALK.

Apiocrinus ellipticus.Lign.93.—Detached ossicula of this small encrinite are abundant in the White Chalk; the receptacle is known to the quarrymen by the name of "bottle." The pieces composing the column are cylindrical in the upper part, and elliptical and angular in the lower, and are articulated by a transversely-grooved surface. The two upper joints are enlarged, and support the receptacle, which is smooth and round (fig.1). The column has articulated side-arms, and the base numerous jointed processes of attachment, which, when found apart from the column, have been mistakenfor a distinct type, and named "Stag's-horn Encriniter."[277]The specimens figuredLign.93, show the essential characters of this crinoid; when perfect, this species must have borne a general resemblance to the Pear Encrinite of Bradford.

[277]Pict. Atlas, pl. xlvii.fig.31, p. 113. In the same plate there are figures of several specimens of detached portions of the stem of this species from the Kentish Chalk.

Lign. 93. Apiocrinites.Chalk, Lewes.Fig.1.—Apiocrinus ellipticus, × 3.1a.—Part of the elliptical portion of the column, with a side-arm.1b.—Portion of the same, magnified.1c.—The articulating surface of an ossicle.2.—Ossicle ofA. flexuosus. (M. D'Orbigny.).3.—Portion of the cylindrical stem.

Bourqueticrinus(D'Orbigny).Lign.91,fig.11.—Detached ossicles of other species belonging to the same genus, or to allied genera, are frequently met with in the Kentish and Sussex chalk. A common form is that figured inLign.91, which is part of the receptacle of a crinoid, named as above; it differs from the other Apiocrinites of the chalk in the articulating surfaces of the ossicles not being radiated,and in the receptacle, which is small and pyriform, not having a distinct cavity; there is only a median canal, which is seen in a vertical section: but the entire structure of the summit does not appear to be shown in any specimens hitherto observed.

Encrinus liliiformis(Lily Encrinite).Lign.91,fig.6.—This exquisite Crinoid is equally interesting and attractive to the amateur collector and the naturalist. Its remains do not occur in the British strata, and are only known in the muschelkalk of Lower Saxony. The specimens in this country are chiefly from Erkerode, in Brunswick; they are found in a layer, about eighteen inches thick, of a soft argillaceous cream-coloured limestone, chiefly made up of trochites, detached ossicula, and a few fragile shells and corals.

The receptacle of the Lily Encrinite is smooth, and in the form of a depressed vase; its base is composed of five plates, upon which are placed three successive series of other plates, with the uppermost of which the arms articulate. The stem is formed of numerous perforated round ossicles, articulated to each other by radiated grooved surfaces, and becoming somewhat pentangular, and alternately larger and smaller, towards the summit, to which the receptacle is fixed; a construction admitting great freedom of motion.[278]

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