Anthozoa

Alcyonaria.—In this sub-class the zooid has very constant anatomical characters, differing in some important respects from the Actinian zooid, which has been taken as a type. There is only one ciliated groove, the sulcus, in the stomodaeum. There are always eight tentacles, which are hollow and fringed on their sides, with hollow projections or pinnae; and always eight mesenteries, all of which are complete, i.e. inserted on the stomodaeum. The mesenteries are provided with well-developed longitudinal retractor muscles, supported on longitudinal folds or plaits of the mesogloea, so that in cross-section they have a branched appearance. These muscle-banners, as they are called, have a highly characteristic arrangement; they are all situated on those faces of the mesenteries which look towards the sulcus. (fig. 4). Each mesentery has a filament; but two of them, namely, the pair farthest from the sulcus, are longer than the rest, and have a different form of filament. It has been shown that these asulcar filaments are derived from the ectoderm, the remainder from the endoderm. The only exceptions to this structure are found in the arrested or modified zooids, which occur in many of the colonial Alcyonaria. In these the tentacles are stunted or suppressed and the mesenteries are ill-developed, but the sulcus is unusually large and has long cilia. Such modified zooids are called siphonozooids, their function being to drive currents of fluid through the canal-systems of the colonies to which they belong. With very few exceptions a calcareous skeleton is present in all Alcyonaria; it usually consists of spicules of carbonate of lime, each spicule being formed within an ectodermic cell (fig. 3, B). Most commonly the spicule-forming cells pass out of the ectoderm and are imbedded in the mesogloea, where they may remain separate from one another or may be fused together to form a strong mass. In addition to the spicular skeleton an organic horny skeleton is frequently present, either in the form of a horny external investment (Cornularia), or an internal axis (Gorgonia), or it may form a matrix in which spicules are imbedded (Keroeides, Meistodes).

Nearly all the Alcyonaria are colonial. Four solitary species have been described, viz. Haimea funebris and H. hyalina, Hartea elegans, and Monoxenia Darwinii; but it is doubtful whether these are not the young forms of colonies. For the present the solitary forms may be placed in a grade, Protal-cyonacea, and the colonial forms may be grouped in another grade, Synalcyonacea. Every Alcyonarian colony is developed by budding from a single parent zooid. The buds are not direct outgrowths of the body-wall, but are formed on the courses of hollow out growths of the base or body-wall, called solenia. These form a more or less complicated canal system, lined by endoderm, and communicating with the cavities of the zooids. The most simple form of budding is found in the genus Cornularia, in which the mother zooid gives off from its base one or more simple radiciform outgrowths. Each outgrowth contains a single tube or solenium, and at a longer or shorter distance from the mother zooid a daughter zooid is formed as a bud. This gives off new outgrowths, and these, branching and anastomosing with one another, may form a network, adhering to stones, corals, or other objects, from which zooids arise at intervals. In Clavularia and its allies each outgrowth contains several solenia, and the outgrowths may take the form of flat expansions, composed of a number of solenial tubes felted together to form a lamellar surface of attachment. Such outgrowths are called stolons, and a stolon may be simple, i.e. contain only one solenium, as in Cornularia, or may be complex and built up of many solenia, as in Clavularia. Further complications arise when the lower walls of the mother zooid become thickened and interpenetrated with solenia, from which buds are developed, so that lobose, tufted, or branched colonies are formed. The chief orders of the Synalcyonacea are founded upon the different architectural features of colonies produced by different modes of budding. We recognize six orders—the Stolonifera, Alcyonacea, Pseudaxonia, Axifera, Stelechotokea, and Cornothecalia.

Fig. 5.

A. Skeleton of a young colony of Tubipora purpurea. st, Stolon; p, platform. B. Diagrammatic longitudinal section of a corallite, showing two platforms, p and cup-shaped tabulae, t. (After S.J. Hickson.)

Fig. 6.—Portion of a colony of Coralinum rubrum, showing expanded and contracted zooids. In the lower part of the figure the cortex has been cut away to show the axis, ax, and the longitudinal canals, lc, surrounding it.

In the order Stolonirera the zooids spring at intervals from branching or lamellar stolons, and are usually free from one another, except at their bases, but in some cases horizontal solenia arising at various heights from the body-wall may place the more distal portions of the zooids in communication with one another. In the genus Tubipora these horizontal solenia unite to form a series of horizontal platforms (fig. 5). The order comprises the families Cornulamdae, Syringopordae, Tubipondae, and Favositidae. In the first-named, the zooids are united only by their bases and the skeleton consists of loose spicules. In the Tubipondae the spicules of the proximal part of the body-wall are fused together to form a firm tube, the corallite, into which the distal part of the zooid can be retracted. The corallites are connected at intervals by horizontal platforms containing solenia, and at the level of each platform the cavity of the corallite is divided by a transverse calcareous partition, either flat or cup-shaped, called a tabula. Formerly all corals in which tabulae are present were classed together as Tabulata, but Tubipora is an undoubted Alcyonarian with a lamellar stolon, and the structure of the fossil genus Syringopora, which has vertical corallites united by horizontal solenia, clearly shows its affinity to Tubipora. The Favositidae, a fossil family from the Silurian and Devonian, have a massive corallum composed of numerous polygonal corallites closely packed together. The cavities of adjacent corallites communicate by means of numerous perforations, which appear to represent solenia, and numerous transverse tabulae are also present. In Favosites hemisphaerica a number of radial spines, projecting into the cavity of the corallite, give it the appearance of a madreporarian coral.

In the order Alcyonacea the colony consists of bunches of elongate cylindrical zooids, whose proximal portions are united by solenia and compacted, by fusion of their own walls and those of the solenia, into a fleshy mass called the coenenchyma. Thus the coenenchyma forms a stem, sometimes branched, from the surface of which the free portions of the zooids project. The skeleton of the Alcyonacea consists of separate calcareous spicules, which are often, especially in the Nephthyidae, so abundant and so closely interlocked as to form a tolerably firm and hard armour. The order comprises the families Xeniidae, Alcyonidae and Nephthyidae. Alcyonium digitatum, a pink digitate form popularly known as “dead men’s fingers,” is common in 10-20 fathoms of water off the English coasts.

Fig. 7.—The sea-fan (Gorgonia cavolinii).

Fig. 8.

A. Colony of Pennatula phosphorea from the metarachidial aspect. p, The peduncle. B. Section of the rachis bearing a single pinna, a, Axis; b, metarachidial; c, prorachidial; d, pararachidial stem canals.

In the order Pseudaxonia the colonies are upright and branched, consisting of a number of short zooids whose proximal ends are imbedded in a coenenchyma containing numerous ramifying solenia and spicules. The coenenchyma is further differentiated into a medullary portion and a cortex. The latter contains the proximal moieties of the zooids and numerous but separate spicules. The medullary portion is densely crowded with spicules of different shape from those in the cortex, and in some forms the spicules are cemented together to form a hard supporting axis. There are four families of Pseudaxonia—the Briareidae, Sclerogorgidae, Melitodidae, and Corallidae. In the first-named the medulla is penetrated by solenia and forms an indistinct axis; in the remainder the medulla is devoid of solenia, and in the Melitodidae and Corallidae it forms a dense axis, which in the Melitodidae consists of alternate calcareous and horny joints. The precious red coral of commerce, Corallium rubrum (fig. 6), a member of the family Corallidae, is found at depths varying from 15 to 120 fathoms the Mediterranean Sea, chiefly on the African coast. It owes its commercial value to the beauty of its hard red calcareous axis which in life is covered by a cortex in which the proximal moieties of the zooids are imbedded. Corallium rubrum has been the subject of a beautifully-illustrated memoir by de Lacaze-Duthiers, which should be consulted for details of anatomy.

The Axifera comprise those corals that have a horny or calcified axis, which in position corresponds to the axis of the Pscudaxonia, but, unlike it, is never formed of fused spicules; the most familiar example is the pink sea-fan, Gorgonia cavolinii, which is found in abundance in 10-25 fathoms of water off the English coasts (fig. 7). In this order the axis is formed as an ingrowth of the ectoderm of the base of the mother zooid of the colony, the cavity of the ingrowth being filled by a horny substance secreted by the ectoderm. In Gorgonia the axis remains horny throughout life, but in many forms it is further strengthened by a deposit of calcareous matter In the family Isidinae the axis consists of alternate segments of horny and calcareous substance, the latter being amorphous. The order contains six families—the Dasygorgidae, Isidae, Primnoidae, Muriceidae, Plexauridae, and Gorgoniaae.

In the order Stelechotokea the colony consists of a stem formed by a greatly-elongated mother zooid, and the daughter zooids are borne as lateral buds on the stem. In the section Asiphonacea the colonies are upright and branched, springing from membranous or ramifying stolons. They resemble and are closely allied to certain families of the Cornulariidae, differing from them only in mode of budding and in the dispostion of the daughter zooids round a central, much-elongated mother zooid. The section contains two families, the Telestidae and the Coelogorgidae. The second section comprises the Pennatulacea or sea-pens, which are remarkable from the fact that the colony is not fixed by the base to a rock or other object, but is imbedded in sand or mud by the proximal portion of the stem known as the peduncle. In the typical genus, Pennatula (fig. 8), the colony looks like a feather having a stem divisible into an upper moiety or rachis, bearing lateral central leaflets (pinnae), and a lower peduncle, which is sterile and imbedded in sand or mud. The stem represents a greatly enlarged and elongated mother zooid. It is divided longitudinally by a partition separating a so-called “ventral” or prorachidial canal from a so-called “dorsal” or metarachidial canal. A rod-like supporting axis of peculiar texture is developed in the longitudinal partition, and a longitudinal canal is hollowed out on either side of the axis in the substance of the longitudinal partition, so that there are four stem-canals in all. The prorachidial and metarachidial aspects of the rachis are sterile, but the sides or pararachides bear numerous daughter zooids of two kinds—(1) fully-formed autozooids, (2) small stunted siphonozooids. The pinnae are formed by the elongated autozooids, whose proximal portions are fused together to form a leaf-like expansion, from the upper edge of which the distal extremities of the zooids project. The siphonozooids are very numerous and lie between the bases at the pinnae on the pararachides; they extend also on the prorachidial and metarachidial surfaces. The calcareous skeleton of the Pennatulacea consists of scattered spicules, but in one species, Protocaulon molle, spicules are absent. Although of great interest the Pennatulacea do not form an enduring skeleton or “coral,” and need not be considered in detail in this place.

Fig. 9.

A, Portion of the surface of a colony of Heliopora coerulea magnified, showing two calices and the surrounding coenenchymal tubes. B, Single zooid with the adjacent soft tissues as seen after removal of the skeleton by decalcification. Z1, the distal, and Z2, the proximal or intracalicular portion of the zooid; ec, ectoderm; ct, coenenchymal tubes; sp, superficial network of solenia.

The order Coenothecalia is represented by a single living species, Heliopora coerulea, which differs from all recent Alcyonaria in the fact that its skeleton is not composed of spicules, but is formed as a secretion from a layer of cells called calicoblasts, which originate from the ectoderm. The corallum of Heliopora is of a blue colour, and has the form of broad, upright, lobed, or digitate masses flattened from side to side. The surfaces are pitted all over with perforations of two kinds, viz. larger star-shaped cavities, called calices, in which the zooids are lodged, and very numerous smaller round or polygonal apertures, which in life contain as many short unbranched tubes, known as the coenenchymal tubes (fig. 9, A). The walls of the calices and coenenchymal tubes are formed of flat plates of calcite, which are so disposed that the walls of one tube enter into the composition of the walls of adjacent tubes, and the walls of the calices are formed by the walls of adjacent coenenchymal tubes. Thus the architecture of the Helioporid colony differs entirely from such forms as Tubipora or Favosites, in which each corallite has its own distinct and proper wall. The cavities both of the calices and coenenchymal tubes of Heliopora are closed below by horizontal partitions or tabulae, hence the genus was formerly included in the group Tabulata, and was supposed to belong to the madreporarian corals, both because of its lamellar skeleton, which resembles that of a Madrepore, and because each calicle has from twelve to fifteen radial partitions or septa projecting into its cavity. The structure of the zooid of Heliopora, however, is that of a typical Alcyonarian, and the septa have only a resemblance to, but no real homology with, the similarly named structures in madreporarian corals. Heliopora coerulea is found between tide-marks on the shore platforms of coral islands. The order was more abundantly represented in Palaeozoic times by the Heliolitidae from the Upper and Lower Silurian and the Devonian, and by the Thecidae from the Wenlock limestone. In Heliolites porosus the colonies had the form of spheroidal masses; the calices were furnished with twelve pseudosepta, and the coenenchymal tubes were more or less regularly hexagonal.

Fig. 10.

A, Edwardsia claparedii (after A. Andres). Cap, capitulum; sc, scapus; ph, physa. B, Transverse section of the same, showing the arrangement of the mesenteries, s, Sulcus; sl, sulculus. C, Transverse section of Halcampa. d, d, Directive mesenteries; st, stomodaeum.

Zoantharia.—In this sub-class the arrangement of the mesenteries is subject to a great deal of variation, but all the types hitherto observed may be referred to a common plan, illustrated by the living genus Edwardsia (fig. 10, A, B). This is a small solitary Zoantharian which lives embedded in sand. Its body is divisible into three portions, an upper capitulum bearing the mouth and tentacles, a median scapus covered by a friable cuticle, and a terminal physa which is rounded. Both capitulum and physa can be retracted within the scapus. There are from sixteen to thirty-two simple tentacles, but only eight mesenteries, all of which are complete. The stomodaeum is compressed laterally, and is furnished with two longitudinal grooves, a sulcus and a sulculus. The arrangement of the muscle-banners on the mesenteries is characteristic. On six of the mesenteries the muscle-banners have the same position as in the Alcyonaria, namely, on the sulcar faces; but in the two remaining mesenteries, namely, those which are attached on either side of the sulcus, the muscle-banners are on the opposite or sulcular faces. It is not known whether all the eight mesenteries of Edwardsia are developed simultaneously or not, but in the youngest form which has been studied all the eight mesenteries were present, but only two of them, namely the sulco-laterals, bore mesenterial filaments, and so it is presumed that they are the first pair to be developed. In the common sea-anemone, Actinia equina (which has already been quoted as a type of Anthozoan structure), the mesenteries are numerous and are arranged in cycles. The mesenteries of the first cycle are complete (i.e. are attached to the stomodaeum), are twelve in number, and arranged in couples, distinguishable by the position of the muscle-banners. In the four couples of mesenteries which are attached to the sides of the elongated stomodaeum the muscle-banners of each couple are turned towards one another, but in the sulcar and sulcular couples, known as the directive mesenteries, the muscle-banners are on the outer faces of the mesenteries, and so are turned away from one another (see fig. 10, C). The space enclosed between two mesenteries of the same couple is called an entocoele; the space enclosed between two mesenteries of adjacent couples is called an exocoele. The second cycle of mesenteries consists of six couples, each formed in an exocoele of the primary cycle, and in each couple the muscle-banners are vis-à-vis. The third cycle comprises twelve couples, each formed in an exocoele between the primary and secondary couples and so on, it being a general rule (subject, however, to exceptions) that new mesenterial couples are always formed in the exocoeles, and not in the entocoeles.

Fig. 11.—A, Diagram showing the sequence of mesenterial development in an Actinian. B, Diagrammatic transverse section of Gonactinia prolifera.

While the mesenterial couples belonging to the second and each successive cycle are formed simultaneously, those of the first cycle are formed in successive pairs, each member of a pair being placed on opposite sides of the stomodaeum. Hence the arrangement in six couples is a secondary and not a primary feature. In most Actinians the mesenteries appear in the following order:—At the time when the stomodaeum is formed, a single pair of mesenteries, marked I, I in the diagram (fig. 11, A), makes its appearance, dividing the coelenteric cavity into a smaller sulcar and a large sulcular chamber. The muscle-banners of this pair are placed on the sulcar faces of the mesenteries. Next, a pair of mesenteries, marked II, II in the diagram, is developed in the sulcular chamber, its muscle-banners facing the same way as those of I, I. The third pair is formed in the sulcar chamber, in close connexion with the sulcus, and in this case the muscle-banners are on the sulcular faces. The fourth pair, having its muscle-banners on the sulcar faces, is developed at the opposite extremity of the stomodaeum in close connexion with the sulculus. There are now eight mesenteries present, having exactly the same arrangement as in Edwardsia. A pause in the development follows, during which no new mesenteries are formed, and then the six-rayed symmetry characteristic of a normal Actinian zooid is completed by the formation of the mesenteries V, V in the lateral chambers, and VI, VI in the sulco-lateral chambers, their muscle-banners being so disposed that they form couples respectively with II, II and I, I. In Actinia equina the Edwardsia stage is arrived at somewhat differently. The mesenteries second in order of formation form the sulcular directives, those fourth in order of formation form with the fifth the sulculo-lateral couples of the adult.

Fig. 12.

A, Zoanthid colony, showing the expanded zooids. B, Diagram showing the arrangement of mesenteries in a young Zoanthid. C, Diagram showing the arrangement of mesenteries in an adult Zoanthid. 1, 2, 3, 4, Edwardsian mesenteries.

As far as the anatomy of the zooid is concerned, the majority of the stony or madreporarian corals agree exactly with the soft-bodied Actinians, such as Actinia equina, both in the number and arrangement of the adult mesenteries and in the order of development of the first cycle. The few exceptions will be dealt with later, but it may be stated here that even in these the first cycle of six couples of mesenteries is always formed, and in all the cases which have been examined the course of development described above is followed. There are, however, several groups of Zoantharia in which the mesenterial arrangement of the adult differs widely from that just described. But it is possible to refer all these cases with more or less certainty to the Edwardsian type.

The order Zoanthidea comprises a number of soft-bodied Zoantharians generally encrusted with sand. Externally they resemble ordinary sea-anemones, but there is only one ciliated groove, the sulcus, in the stomodaeum, and the mesenteries are arranged on a peculiar pattern. The first twelve mesenteries are disposed in couples, and do not differ from those of Actinia except in size. The mesenterial pairs I, II and III are attached to the stomodaeum, and are called macromesenteries (fig. 12, B), but IV, V and VI are much shorter, and are called micromesenteries. The subsequent development is peculiar to the group. New mesenteries are formed only in the sulco-lateral exocoeles. They are formed in couples, each couple consisting of a macromesentery and a micromesentery, disposed so that the former is nearest to the sulcar directives. The derivation of the Zoanthidea from an Edwardsia form is sufficiently obvious.

The order Cerianthidea comprises a few soft-bodied Zoantharians with rounded aboral extremities pierced by pores. They have two circlets of tentacles, a labial and a marginal, and there is only one ciliated groove in the stomodaeum, which appears to be the sulculus. The mesenteries are numerous, and the longitudinal muscles, though distinguishable, are so feebly developed that there are no muscle-banners. The larval forms of the type genus Cerianthus float freely in the sea, and were once considered to belong to a separate genus, Arachnactis. In this larva four pairs of mesenteries having the typical Edwardsian arrangement are developed, but the fifth and sixth pairs, instead of forming couples with the first and second, arise in the sulcar chamber, the fifth pair inside the fourth, and the sixth pair inside the fifth. New mesenteries are continually added in the sulcar chamber, the seventh pair within the sixth, the eighth pair within the seventh, and so on (fig. 13). In the Cerianthidea, as in the Zoanthidea, much as the adult arrangement of mesenteries differs from that of Actinia, the derivation from an Edwardsia stock is obvious.

Fig. 13.

A, Cerianthus solitarius (after A. Andres). B, Transverse section of the stomodaeum, showing the sulculus, sl, and the arrangement of the mesenteries. C, Oral aspect of Arachnactis brachiolata, the larva of Cerianthus, with seven tentacles. D, Transverse section of an older larva. The numerals indicate the order of development of the mesenteries.

The order Antipathidea is a well-defined group whose affinities are more obscure. The type form, Antipathes dichotoma (fig. 14), forms arborescent colonies consisting of numerous zooids arranged in a single series along one surface of a branched horny axis. Each zooid has six tentacles; the stomodaeum is elongate, but the sulcus and sulculus are very feebly represented. There are ten mesenteries in which the musculature is so little developed as to be almost indistinguishable. The sulcar and sulcular pairs of mesenteries are short, the sulco-lateral and sulculo-lateral pairs are a little longer, but the two transverse are very large and are the only mesenteries which bear gonads. As the development of the Antipathidea is unknown, it is impossible to say what is the sequence of the mesenterial development, but in Leiopathes glaberrima, a genus with twelve mesenteries, there are distinct indications of an Edwardsia stage.

Fig. 14.

A, Portion of a colony of Antipathes dichotoma. B, Single zooid and axis of the same magnified. m, Mouth; mf mesenterial filament; ax, axis. C, Transverse section through the oral cone of Antipathella minor, st, Stomodaeum; ov, ovary.

There are, in addition to these groups, several genera of Actinians whose mesenterial arrangement differs from the normal type. Of these perhaps the most interesting is Gonactinia prolifera (fig. 11, B), with eight macromesenteries arranged on the Edwardsian plan. Two pairs of micromesenteries form couples with the first and second Edwardsian pairs, and in addition there is a couple of micromesenteries in each of the sulculo-lateral exocoeles. Only the first and second pairs of Edwardsian macromesenteries are fertile, i.e. bear gonads.

The remaining forms, the Actiniidea, are divisible into the Malacactiniae, or soft-bodied sea-anemones, which have already been described sufficiently in the course of this article, and the Scleractiniae (= Madreporaria) or true corals.

Group A.

Family I. Zaphrentidae.—Solitary Palaeozoic corals with an epithecal wall. Septa numerous, arranged pinnately with regard to four principal septa. Tabulae present. One or more pits or fossulae present in the calicle. Typical genera—Zaphrentis, Raf. Amplexus, M. Edw. and H. Streptelasma, Hall. Omphyma, Raf.

Family 2. Turbinolidae.—Solitary, rarely colonial corals, with radially arranged septa and without tabulae. Typical genera— Flabellum, Lesson. Turbinolia, M. Edw. and H. Caryophyllia, Lamarck. Sphenotrochus, Moseley, &c.

Family 3. Amphiastraeidae.—Mainly colonial, rarely solitary corals, with radial septa, but bilateral arrangement indicated by persistence of a main septum. Typical genera—Amphiastraea, Étallon. Thecidiosmilia.

Family 4. Stylinidae.—Colonial corals allied to the Amphiastraeidae, but with radially symmetrical septa arranged in cycles. Typical genera—Stylina, Lamarck (Jurassic). Convexastraea, D’Orb. (Jurassic). Isastraea, M. Edw. and H.(Jurassic). Ogilvie refers the modern genus Galaxea to this family.

Group B.

Family 5. Oculinidae.—Branching or massive aporose corals, the calices projecting above the level of a compact coenenchyme formed from the coenosarc which covers the exterior of the corallum. Typical genera—Lophohelia, M. Edw. and H. Oculina, M. Edw. and H.

Family 6. Pocilloporidae.—Colonial branching aporose corals, with small calices sunk in the coenenchyme. Tabulae present, and two larger septa, an axial and abaxial, are always present, with traces of ten smaller septa. Typical genera—Pocillopora, Lamarck. Seriatopora, Lamarck.

Family 7. Madreporidae.—Colonial branching or palmate perforate corals, with abundant trabecular coenenchyme. Theca porous; septa compact and reduced in number. Typical genera— Madrepora, Linn. Turbinaria, Oken. Montipora, Quoy and G.

Family 8. Poritidae.—Incrusting or massive colonial perforate corals; calices usually in contact by their edges, sometimes disjunct and immersed in coenenchyme. Theca and septa perforate. Typical genera—Porites, M. Edw. and H. Goniopora, Quoy and G. Rhodaraea, M. Edw. and H.

Group C.

Family 9. Cyathophyllidae.—Solitary and colonial aporose corals. Tabulae and vesicular endotheca present. Septa numerous, generally radial, seldom pinnate. Typical genera—Cyathophyllum, Goldfuss (Devonian and Carboniferous). Moseleya, Quelch (recent).

Family 10. Astraeidae.—Aporpse, mainly colonial corals, massive, branching, or maeandroid. Septa radial; dissepiments present; an epitheca surrounds the base of massive or maeandroid forms, but only surrounds individual corallites in simple or branching forms. Typical genera—Goniastraea, M. Edw. and H. Heliastraea, M. Edw. and H. Maeandrina, Lam. Coeloria, M. Edw. and H. Favia, Oken.

Family 11. Fungidae.—Solitary and colonial corals, with numerous radial septa united by synapticulae. Typical genera— Lophoseris, M. Edw. and H. Thamnastraea, Le Sauvage. Leptophyllia, Reuss (Jurassic and Cretaceous). Fungia, Dana. Siderastraea, Blainv.

Group D.

Family 12. Eupsammidae.—Solitary or colonial perforate corals, branching, massive, or encrusting. Septa radial; the primary septa usually compact, the remainder perforate. Theca perforate. Synapticula present in some genera. Typical genera—Stephanophyllia, Michelin. Eupsammia, M. Edw. and H. Astroides, Blainv. Rhodopsammia, M. Edw. and H. Dendrophyllia, M. Edw. and H.

Group E.

Family 13. Cystiphyllidae.—Solitary corals with rudimentary septa, and the calicle filled with vesicular endotheca. Genera—Cystiphyllum, Lonsdale (Silurian and Devonian). Goniophyllum, M. Edw. and H. (In this Silurian genus the calyx is provided with a movable operculum, consisting of four paired triangular pieces, the bases of each being attached to the sides of the calyx, and their apices meeting in the middle when the operculum is closed). Calcecla, Lam. (In this Devonian genus there is a single semicircular operculum furnished with a stout median septum and numerous feebly developed secondary septa. The calyx is triangular in section, pointed below, and the operculum is attached to it by hinge-like teeth.)

Authorities.—The following list contains only the names of the more important and more general works on the structure and classification of corals and on coral reefs. For a fuller bibliography the works marked with an asterisk should be consulted: * A. Andres, Fauna und Flora des Golfes von Neapel, ix. (1884); H.M. Bernard, “Catalogue of Madreporarian Corals” in Brit. Museum, ii. (1896), iii. (1897); * G.C. Bourne, “Anthozoa,” in E. Ray Lankester’s Treatise on Zoology, vol. ii. (London, 1900); G. Brook, “Challenger Reports,” Zoology, xxxii. (1899) (Antipatharia); “Cat. Madrep. Corals,” Brit. Museum, i. (1893); D.C. Danielssen, “Report Norwegian North Atlantic Exploring Expedition,” Zoology, xix. (1890); J.E. Duerden, “Some Results on the Morphology and Development of Recent and Fossil Corals,” Rep. Brit. Association, 1903, pp. 684-685; “The Morphology of the Madreporaria,” Biol. Bullet, vii. pp. 79-104; P.M. Duncan, Journ. Linnean Soc. xviii. (1885); P.H. Gosse, Actinologia britannica (London, 1860); O. and R. Hertwig, Die Actinien (Jena, 1879); R. Hertwig, “Challenger Reports,” Zoology, vi. (1882) and xxvi. (1888); * C.B. Klunzinger, Die Korallthiere des Rothen Meeres (Berlin, 1877); * G. von Koch, Fauna und Flora des Golfes van Neapel, xv. (1887); Mitth. Zool. Stat. Neapel, ii. (1882) and xii. (1897); Palaeontographica, xxix. (1883); (also many papers in the Morphol. Jahrbuch from 1878 to 1898); F. Koby, “Polypiers jurassiques de la Suisse,” Mem. Soc. Palaeont. Suisse, vii.-xvi. (1880-1889); A. von Kölliker, “Die Pennatuliden,” Abh. d. Senck. Naturf. Gesell. vii.; * “Challenger Reports,” Zoology, i. Pennatulidae (1880); Koren and Danielssen, Norske Nordhaus Exped., Alcyonida (1887); H. de Lacaze-Duthiers, Hist. nat. du corail (Paris, 1864); H. Milne-Edwards and J. Haime, Hist. nat. des coralliaires (Paris, 1857); H.N. Moseley, “Challenger Reports,” Zoology, ii. (1881); H.A. Nicholson, Palaeozoic Tabulate Corals (Edinburgh, 1879); M.M. Ogilvie, Phil. Transactions, clxxxvii. (1896); E. Pratz, Palaeontographica, xxix. (1882); J.J. Quelch, “Challenger Reports,” Zoology, xvi. (1886); * P.S. Wright and Th. Studer, “Challenger Reports,” Zoology, xxxi. (1889).