and their more or less horizontal and perfect tabula, recall the Tubiporina amongst the order of the Alcyonaria.

The Alcyonaria are Actinozoa which are separated by MM. Milne-Edwards and Jules Haime from the Zoantharia on account of the pinnate structure of the tentacles, and from these important organs being invariably eight in number.

The zoantharian tentacles, on the contrary, are simple or irregularly ramified, and increase in number with age.

The Alcyonaria are divided into the families of the Alcyonidæ, the Gorgonidæ, and the Pennatulidæ.

The first two families have an adherent corallum, and the last consists of free forms.

The Alcyonida have no hard central axis, but this characterizes the Gorgonidae.

Now the Cornularinæ, Telestinæ, and Alcyoninæ, subfamilies of the Alcynidæ, are clearly allied to the Tubiporina by their soft structures; but the hard external structures of this subfamily are only faintly shown in the spiculate scoriaceous conditions of the external tegument of Nephthya, Spoggodes, and Paralcyonium. The polypes of Nephthya and Paralcyonium enter their spiculate and dense external covering when they contract; but the hard structures of Spoggodes celosia, Lesson, are very slightly developed.

Tubipora, Lamarck.

TUBIPORA (pars), Linnæus.

The genus has been examined by MM. Milne-Edwards and Jules Haime. with their usual care and acumen.

The specimens of Tubipora are so common that the descriptions of these authors concerning the hard parts of the corallum can readily be followed.

The corallites are formed principally by a tabular wall, the tissue of which is calcareous and readily fractured. There are no septa, but there are rudimentary tabulæ, which cut off the visceral cavity into more or less perfect stages. The corallites are cylindrical, and usually attain an equal height; but they do not touch each other, for they are united by a peritheca, which is only seen here and there in distinct floors. The budding takes place from the connecting peritheca, which is therefore a true cœnenchyma, and not like that of Solenastræa. Were the corallites in contact the appearance of Chatetes would be presented; so that the presence of the coenenchyma is the differentiating structure. It is only of generic value, and thus there is a very strong reason for associating the Chatetinæ and all the other fossils with long tubular structures, no septa, and tabula with the Alcyonidae in the subfamily Tubiporina and near the genus Tubipora. These remarks are subject, of course, to the consideration whether the views of Agassiz already noticed are correct.

Reuss's genus Stylophyllum (Gosau Chalk) cannot be associated with the Alcyonidæ, for the species has septa. The corallites are united by their walls without there being a cœnenchyma, and the walls are imperforate. The junction of the corallites takes place by means of an epitheca.

The junction may occur at any part of the corallite.

The resemblance of Stylophyllum to some of the Halysitinæ (Ed. & H.)* necessitates an examination of their structural peculiarities.

*Op. cit. vol. iii. p. 286.

1871.

K

MM. Milne-Edwards and Jules Haime differentiate the Halysitinæ as follows:

"The corallum is compound, but its corallites unite imperfectly, and constitute lamellar expansions or long fasciculi; they are either free on two sides, or are united together by 'expansions murales.'"

The septa are small, but usually very distinct; finally the walls are well developed and aporose.

The genera are:- Halysites, Fischer; Syringopora, Goldfuss; Thecostegites, Ed. & H. (Harmodites, Michelin); Conostegites, Ed. & H.; Fletcheria, Ed. & H.

Halysites. The species are invariably formed by corallites which are joined on two sides, and which in transverse outline resemble links of a chain. The epitheca is very strong, and unites the corallites perfectly where they are in contact from the base to the calice. Septa 12. Tabule horizontal and well developed. (Silurian.)

Thecostegites. The corallites have septa, horizontal tabulæ, and an exotheca unites them, and it is more or less tabular in structure, and exists in stages like the Tubipora. In T. parvula the conenchyma is nearly compact. (Devonian.)

Conostegites. There are numerous septal striæ, which mark also the smooth and convex surfaces of the tabulæ. The tabulæ are more or less infundibuliform, and the epitheca unites the corallites here and there. Syringopora. The corallum is fasciculate; the corallites are cylindrical and very long, parallel, and free laterally, except where horizontal tubes connect them. The walls are well developed, and clothed with a strong epitheca; septa exist. The tabulæ are infundibuliform.

Fletcheria. The corallum is fasciculate; the corallites are cylindrical, close, and long. The epitheca is complete; septa exist. Tabulæ horizontal and well developed. No intercorallite tubes or expansions of epitheca. Gemmation calicular.

It is evident that some of these genera are very slightly allied; for instance, Syringopora and Fletcheria, and both of them and Halysites.

Halysites, with its stout epitheca and simple tabule with non-tubular joints, is a very definite form.

Thecostegites should belong to the Milleporida.

Conostegites, with infundibuliform tabulæ, is related to Halysites as Michelinia is to Favosites.

Fletcheria is altogether aberrant.

The Halysitinæ comprehend, according to this analysis, Halysites, Fischer; Stylophyllum, Reuss; Conostegites, Ed. & H.

The genera Syringopora and Fletcheria will be considered further on. The subfamily of the Pocilloporinæ contains the genera Pocillopora and Cœnites.

Pocillopora has septa (and my specimens show 12), which, even in fossil specimens, mark the top of the tabulæ. There is a columellary swelling on its tabulæ. The conenchyma is very stout and thick in old portions of the corallum, less so where growth has just ceased, and the cœnenchyma barely exists where the corallites or calices are developing. It is cellular at first, and then fills up with calcite and other coral salts.

Fossil forms have been described by Reuss and myself from the Cainozoic formations.

Canites resembles Pocillopora in a certain density of its cœnenchyma, but differs in only having three tooth-like septa, like the genus Alveolites.

The number of septa and the habit of growth of the two genera separate them very widely; and the propriety of connecting the last-named one with the Milleporidae must be considered.

There are four genera in the family of the Seriatoporida :-Seriatopora, Dendropora, Rhabdopora, Trachypora.

The family is characterized by the continual growth of the lower parts of the corallites and the rarity of tabulæ.

Seriatopora is a recent genus, and therefore those associated with it must be carefully examined.

Dendropora, Michelin, is clearly too closely allied to Rhabdopora to be separated generically.

Rhabdopora, formed for the Dendropora megastoma, McCoy, by MM. MilneEdwards and Jules Haime, has only one species, the diagnosis of which is as follows:

Cœ

Rhabdopora megastoma, M'Coy, sp.-The corallum is branching. Branches four-sided, starting from the stem at an angle of 70°, and very equal. nenchyma granulated or subechinulated and obscurely striated. Calices in vertical series on each face of the branches. Septa (teeth) 12 in number and subequal.

It is impossible to separate this from Seriatopora, for the four-sided suture of the branches is only a specific (if that) distinction.

Trachypora appears to be an Alcyonarian.

The distinction between Pocillopora and Seriatopora is not generic, and therefore these genera and Dendropora (for Dendropora and Rhabdopora are equal, and the first name is the oldest) are absorbed in one. Oken's name Acropora (1815) may be used as the generic term :-ACROPORA (Seriatopora, Lamarck; Pocillopora, Lamarck; Dendropora, Michelin ; Rhabdopora, Ed. & Haime).

All the species of the absorbed genera should take the generic name of Acropora, and the family becomes that of the Acroporinæ. Thus the sharp distinction between the recent and Palæozoic forms is partly smoothed down, and the old Dendropora and Rhabdopora were doubtless the ancestral forms of the recent Acropora. Cœnites cannot be associated with the

family.

The family of the Thecidea is characterized by well-formed septa, which are prolonged throughout the visceral chamber, well-developed tabula, which grow like dissepiments upon the sides of the septa, and these last do not spring from the upper surface of the tabulæ, as in some Tabulata. The walls are solid, compact, and united.

The corals contained in the family are all Silurian forms, so far as is known at present.

Thecia, Ed. & Haime. It is a most remarkable fact that this genus, the species of which have no true wall, but a dense conenchyma between septal prolongations or costa, should here give the family name. Thecia Swinderniana, Goldfuss, sp., has been called Agaricia, Porites, Astreopora, and Palæopora by different authors, so that its classificatory position may well be a matter of doubt. It is not in the least allied to Columnaria, which has solid walls, and which fulfils all the characteristics of the Thecida.

In Thecia, Ed. & H., there is a long visceral cavity surrounded by a dense tissue, as in Millepora, through which the septa, or rather the costa, run. What is the structure of Plasmopora and Propora but that of Thecia slightly modified. The genus clearly must be associated with them amongst the Milleporida.

Columnaria is a fine form; the great septa (12 to 18) and tabulæ, with the compact walls, distinguish it at once. Col. alveolata is a Lower Silurian form, C. Gothlandica is Upper Silurian. It is a most important genus, and its affinities will be noticed.

The Favositida have a massive corallum without conenchyma, septa, and perforate walls; that is, there are openings which permit the visceral cavity of one corallite to communicate with that of another in several places. The following genera are included by MM. Milne-Edwards and Jules Haime :Favosites, Emmonsia, Michelinia, Roemeria, Koninckia, Alveolites.

:

Favosites is the typical genus. In some species the mural foramina are scanty in number, in others numerous; and they are even in relation with the angles of the wall, especially in F. alveolaris.

The earliest species of the genus are Lower Silurian, for instance :-F. Gothlandica, F. multipora, F. aspera, F. Forbesi (which ranges through to the Upper Silurian), and F. fibrosa (having the same vertical range, and is found as a Devonian fossil).

F. Hisingeri has the same range as F. fibrosa. F. cristata and F. cervicornis are the same, and the range is from the Upper Silurian of England to the Devonian of Russia.

The species which are Devonian, and do not range above or below, are :— F. Goldfussi, F. basaltica, F. polymorpha, F. alveolaris, F. pediculata, F. Tchihatcheff, and F. mammillaris. The only known Carboniferous Favosites is F. parasitica, and it is a degenerate form.

F. Gothlandica has rounded processes encircling the mural pores, and the projections formed upon one fit against those of the neighbouring corallite. F. multipora has three vertical series of pores, and its walls are almost as perforate as some Alveopora.

The tabulæ are almost universally horizontal in the Favosites, but some are wavy in their course; and the septa are a series of vertical spines which vary in size according to the cycle, and are often referable to three cycles in six systems. In some there is a faint columellary swelling on the tabulæ.

A careful examination of the species proves that the earliest known forms are as highly developed as the Devonian, but that the species parasitica is dwarfed.

Emmonsia has imperfect tabulæ. The tabulæ are vesicular at the sides, or dissepimental, and they communicate more or less with each other.

Romeria has infundibuliform tabulæ, and the species is Devonian. Koninckia is an Upper Cretaceous form; it has thin and nearly horizontal tabulæ, thin walls very much perforated, and six series of large spiny septa. Michelinia has irregular and vesicular (dissepimental) tabulæ, and simple striæ for septa (Devonian and Carboniferous). The alliance of Michelinia, Roemeria, and Emmonsia is very evident. Mr. Kent has written a most interesting description of Favositipora (Kent), Ann. & Mag. Nat. Hist. 1870, vol. vi. p. 384, which unites the Favositinæ and the Favositidæ.

Alveolites offers the same objection to being united to Favosites that Conites docs to Pocillopora; in fact Alveolites is a Conites with perforated walls, and it is proposed to deal with both genera by disassociating them from their recognized families.

Syringopora I propose uniting with the Favositidæ, as it has tubular connexions between the visceral centres of the corallites, which are foreshadowed in F. Gothlandica.

After this analysis of the Tabulata, it is necessary to state the opinions of Prof. Agassiz respecting their Hydrozoan characteristics.

ON THE BRITISH FOSSIL CORALS.

UNIVESITY

Prof. Agassiz (senior) writes as follows in the American Journal of Science and Arts,' 2nd series, vol. xxvi. p. 140, November 1858:LIFORY

"The animals of Millepora are Hydroid Acalephs and not polyps;" that is to say, they are Hydrozoa and not Actinozoa. The résumé of several letters to Dana is given at the same place. "I have seen," writes Agassiz, "in the Tortugas something very unexpected. Millepora is not an actinoid polyp but a genuine Hydroid, closely allied to Hydractinia. This seems to carry the whole group of Favositidæ over to the Acalephs, and displays a beautiful array of this class from the Silurian to this day."

Dana adds a note to this statement. "The drawings of Professor Agassiz which have been sent us for examination are so obviously Hydractinian in most of their characters that no one can question the relation. With regard to the reference of all the Favositide (a group including Favosites, Fenestella, Pocillopora, &c., as well as the minuter Millepora, Chatetes, &c.) to the Acaleph class, direct evidence is not yet complete, as the animal of the Pocillopora has not been figured by any author on zoophytes. From the specimens of the species of this genus which I procured in the Pacific, I never obtained a clear view of the polyps, and hence made no figure. The brief description on page 523 of my Report may be reasonably doubted until confirmed by new researches. The much larger cells in Pocillopora, Favosites, and Fenestella than in Millepora, and the frequently distinct rays in these cells, are the characters I had mentioned to Prof. Agassiz as suggesting a doubt as to their being Acalephs, and to this what follows above relates."

Agassiz observes, in a subsequent letter, after observing that the Sideroporæ obviously are polyps, "There are two types of radiating lamella which are not homologous. In true polyps (excluding Favositidæ as Hydroids) the lamellæ extend from the outer body-wall inward along the whole height of that wall, and the transverse partitions reach only from one lamella to the other, so that there is no continuity between them, while the radiating lamella are continuous from top to bottom in each cell. In Milleporida the partitions are transverse and continuous across the cells; so are they in Pocillopora and in all Tabulata and Rugosa; while the radiating lamella, where they exist, as in Pocillopora and many other Favositida, rise from these horizontal floors, and do not extend through the transverse partitions; indeed they are limited within the spaces of two successive floors, or to the upper surface of the last. A careful comparison of the corallum of Millepora and Pocillopora with that of Hydractinia has satisfied me that these radiating partitions of the Favositidæ, far from being productions of the body-wall, are foot-secretions, to be compared to the axis of the Gordonia corallum &c., and their seeming radiating lamellæ to the vertical groove or keel upon the surface of the latter, which, reduced to a horizontal projection, would also make the impression of radiating lamellæ in the foot of the polyp. If this be so, you see at once that apparent radiating lamella of the Favositidæ do no longer indicate an affinity with the true polyps, but simply a peculiar mode of growth of the corallum; and of these we have already several types, that of Actinoids, that of Alcyonoids, that of Bryozoa, that of Millepora, and other corallines, to which we now add that of Hydroids. Considering the subject in this light, is there any further objection to uniting all the Favositida with the Hydroids? Sideropora and Alveopora being of course removed from the Favositidæ. It is a point of great importance in a geological point of view, and for years I have been anticipating some such result, as you may see by comparing my remarks in the American Journal,' May 1854, p. 315. If all the Tabulata and Rugosa are Hydroids, as I believe them to be, the class of