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I do not consider that the Tubulosa belonged to the Madreporaria, but that they were Alcyonarians.
It is very certain that some Aporose, Perforate, and Rugose corals have tabulæ, and that their existence cannot remove the forms from their received zoological position into the separate section of Tabulata.
Thus the well-known Aporose coral of the deep sea, Lophohelia pro
more than portions of Stromatopora which enclose the corallites and grow simultaneously with them.
I have altered the generic characters of Battersbyia, in consequence of a careful examination of the old and the two new species. It is as follows:-Corallum fasciculate and branching; corallites tall, cylindrical, unequal in size and distance; septa numerous and following no apparent cyclical order.
Endotheca very abundant: it is vesicular, and there are no tabulæ. Epitheca, costæ, and cœnenchyma wanting. The wall is stout, and the septa spring from wedge-shaped processes. The columellary space is occupied by vesicular endotheca. Gemmation extracalicular and calicular from buds having only five septa.
There are three species:
In Battersbyia gemmans the buds which develop more than five septa grow into corallites, which are destined to bud again from the external wall, and the buds which develop five septa produce other buds from their interseptal loculi; the buds thus developed resemble the corallites with more than three septa. This curious alternation of gemmation has not been noticed in any other genus.
The genera Battersbyia and Heterophyllia (Phil. Trans. loc. cit.) have much in common. They have a stout wall, a vesicular and dissepimental endotheca, delicate septa, very irregular in their number, and neither tabular epitheca nor a quaternary septal arrangement. The genus Battersbyia has nothing to ally it to the Rugosa or the Tabulata. Hetero-phyllia has in some of its species the solitary septum or vacancy which is so often observed in the Cyathophyllida. Its costal wall and endotheca connect it with the Mesozoic and recent Astræida.
The singular septal development of Battersbyia is witnessed in the fasciculate Liassic Astræida. The pentameral arrangement of the Battersbyian septa is not unique, for Acanthocenia Rathieri, D'Orb., of the Neocomian has only five septa, and so have the species of Pentaconia, all of which are from the same great formation. The proper Liassic and some of the Lower Oolitic Thecosmiliæ and Calamophylliæ represent and are allied by structure to Battersbyia. The highly specialized characters of the Heterophylliæ, especially of H. mirabilis, could hardly be perpetuated during great and prolonged emigrations, so that the genus appears to be without representatives in the secondary rocks. Its alliance to Battersbyia, however, is evident enough.
The genus Heterophyllia, M'Coy, was examined by me in 1867, and the study of several new species of it rendered a fresh diagnosis requisite.
The following description of the diagnosis appeared in my essay on the genera Heterophyllia, &c., already noticed:
"The corallum is simple, long, and slender. The gemmation takes place around the calicular margin, and is extracalicular. The septa are either irregular in number and arrangement, or else are six in number and regular. The costs are well developed, and may be trabecular, spined, and flexuous. The wall is thick; there is no epitheca, and the endotheca is dissepimental."
The genus may be subdivided into a group with numerous septa, and a group with six septa.
In the first the rugose type is faintly, and in the last the hexameral arrangement is well observed.
The dense wall and the dissepimental endotheca prove that the type of the Mesozoic Coral-fauna was foreshown.
The endotheca varies in quantity in the different species, and it resembles the tabular arrangement; but even when this is the case and the cross structures are well developed and numerous, they do not stretch over the axial space, so as to shut out cavities as if they were floors; they do not close in the whole of the visceral and interlocular
lifera, Pallas, sp., may have some of its corallites subdivided by perfect tabulæ; the species of Cyathophora of the Oolites also; yet it would be a most objectionable and improper proceeding to remove these genera from their recognized alliances. I found an Astræopora in the Museum at Liverpool with tabulæ ; and Mr. Kent has pointed out the perforate affinities of Koninckia and of the form he has published. Some Rugosa have perfect tabulæ, others have them not; and in Cyclophyllum and Clisiophyllum dissepiments exist in some parts of a corallum and not in others, where they are replaced by tabulæ. This interesting fact may be gleaned from James Thomson's sections taken from the Scottish corals.
Nevertheless there are forms which are essentially tabulate, and not rugose, but which, so far as their hard and septal structures are concerned, may be aporose in one instance and perforate in another; for instance, Columnaria and Favosites. These forms may still provisionally be considered Tabulata.
Alliances.-The Lower Cretaceous and Neocomian corals appear to connect the oldest and the newest faunas, and to form an excellent starting-point both for the study of the Tertiary as well as for the Paleozoic forms. It will be readily observed that the succession of genera and species from the lower Cretaceous horizon to the present day is gradual; and that although many forms died out, still the general appearance of the consecutive faunas, such as those of the Middle and Upper Cretaceous, the Nummulitic, the Oligocene, the Miocene, the Pliocene, and of the two great faunas of the present day, presents a remarkable similarity of what is usually called "facies." The similarity between the Lower Cretaceous fauna and that of the Miocene has been treated of elsewhere *, and the analogies of the mid-tertiary corals and those of the Pacific also. Moreover since the last Report was read the distinction between reef, deep-sea, and littoral corals has been more satisfac'torily established, and the reason why consecutive faunas upon the same areas could not possibly be identical, even as regards the genera, has been explained +.
As the Coral-faunas are studied from those of recent date backwards in time, extinct forms are met with which gradually fill up the spaces in the very natural received classification, and it is perfectly evident that the existing species were foreshadowed in the past. A great number of existing species lived in the so-called Pliocene, and not a few in the Miocene ‡. Reuss's admirable researches amongst the vast reefs which are of an intermediate age between the Flysch and the typical coral districts of the Miocene age, have carried back the homotaxis of the existing coral areas to a time which has hardly been recognized by British geologists, but whose fossils are clearly
cavities in a horizontal plane. In some species the dissepiments are curved, and are as incomplete as when they are more or less horizontal in others, and vesicular endotheca exists, more or less, in nearly all the forms.
There are no true tabulæ, and the dissepiments do not interfere in any way with the passage of the septa from the lowest part of the corallum to the calice. There are eight species of Heterophyllia :—
Heterophyllia grandis, M'Coy.
Heterophyllia M'Coyi, Duncan.
The first two are found in the Carboniferous limestone of Derbyshire, and the others in the Scottish Carboniferous strata (see Phil. Trans. 1867, p. 643 et seq.).
* West-Indian Foss. Corals (P. M. Duncan, Quart. Journ. Geol. Soc. xxiv. p. 28).
+ Coral Faunas of Europe (Quart. Journ. Geol. Soc. xxvi. p. 51 et seq.).
Corals of Porcupine Expedition (Proc. Royal Society, xviii. p. 289).
represented at Brockenhurst. In the great reefs of the Castel-Gomberto district there are the remains of a larger coral-fauna than that which now exists in the Caribbean Sea; and although a profound Flysch exists between them and the reefs in the Oberburg district, indicating great oscillations of the area and vast changes in the life of the time, still the genera which contribute so largely to the formation of modern reefs are found represented in abundance in the lowest reefs, which clearly belong to the Nummulitic period.
Our Eocene corals and those found at Brockenhurst are the stunted offshoots of the faunas which flourished at Oberburg and in the Vicentine, but nevertheless some of their species are closely allied to those of much later geological date.
Without the assistance of the labours of Reuss and D'Achiardi zoophytologists could not have imagined that the well-known coral-faunas of the Hala Mountains of Sindh, of the Nummulitic deposits of the Maritime Alps and Switzerland, and of the London and Paris basins were but fractions of a fauna which was probably richer in species than any modern coral tract; and this welcome aid proves the impropriety of neglecting foreign paleontology, even when writing reports like the present, and which treat of the productions of the rocks of a small area. The impossibility of comparing with any satisfaction the Nummulitic coral-fauna and that of the Upper Chalk is obvious; because the Nummulitic fauna, so far as it is known to us, was either a reef or a comparatively shallow-water one, whilst the corals of the Upper Chalk were dwellers in a deep sea, where reef species cannot and could not exist. We must seek to compare the Upper Cretaceous corals with the deep-sea forms of the Nummulitic, but unfortunately they are not yet found*.
The Lower Cretaceous corals of Great Britain were the contemporaries of the reef-builders of the Gosau and equivalent formations, and thus deep-sea and reef species were contemporaneous, as they are at the present time, but they were separated by wide distances. The comparison of the reef-fauna and that of the deep sea is in this instance as futile as it would be at the present time; but we may compare the reef-fauna of Gosau with that of the Nummulitic, Oligocene, Miocene, and existing reefs, and not without benefit and good results, for there are persistent species which unite the whole together.
A comparison may also be instituted between the deep-sea coral-faunas of the Chalk and those which flourished at corresponding depths in the succeeding geological epochs. Thus, thanks to Messrs. Wyville Thomson, Carpenter, and Jeffreys, I have been able to assert the extraordinary homologies between the deep-sea Cretaceous corals and those which now exist to the west of these islands. These results are being published by the Zoological Society. The present arrangement of coral genera in and about reefs was foreshadowed as early as the Eocene, and such assemblages of genera existed in those old reefs as would characterize the coral life of atolls in the Caribbean Sea and in the raised reefs of the Pacific Ocean. The genera Madrepora, Alveopora, Porites, Heliastræa, and Millepora were represented in the Oberburg, and their species constitute the bulk of existing reefs. It is important to be thus able, from the labours of MM. Milne-Edwards, J. Haime, and Reuss, to determine the existence of Perforate and Tabulate corals in the earliest tertiaries, for interesting links are thus offered to the paleontologist by which the older and the newer faunas are connected. Such researches diminish the importance of the break between the early Tertiary fauna and the present, and also, to a
* See P. M. Duncan on a new Coral from the Crag, and on the persistence of Cretaceous types in the deep sea (Quart. Journ. Geol. Soc. xxvii. pp. 369 & 434).
certain extent, that between the Paleozoic and recent faunas. Thus the finding of species of the great Perforate genus Madrepora in the Oberburg carries the genus a step further back than their discovery in the Oligocene of Brockenhurst, and when taken into consideration with the presence of the Stephanophyllia, a perforate simple coral, in the Crag, Eocene, and Lower Cretaceous deposits, and with Actinacis, a highly developed compound form, in the Lower Cretaceous strata of Gosau, the immense break between the next form of the family and the existing is materially diminished. The next form is not met with until the Carboniferous deposits of Indiana are reached in a downward course; and we owe to the late Jules Haime the knowledge of the structures of Palæacis cuneiformis, Haime, MS., from Spurgeon Hill, Indiana. It is indeed remarkable that the vast coralliferous strata which intervene between the Carboniferous and the Lower Chalk should not present a satisfactory proof of the existence of those members of the existing great reef-building family. There is a curious fact which may be taken for what it is worth in considering the absence of genera which have been represented in some ancient deposits and which have not been found in intermediate strata. Thus the existing West-India reefs contain abundance of the species of the genus Madrepora and Millepora; indeed they, with the forms of Porites, constitute the bulk of the formations. Now, although Porites is common in the Miocene reefs of the area, the others are very rare, for the coral structures were principally composed of tabulate forms and Heliastraans. Yet we know that before the Miocene reefs flourished, Madreporæ and Millepora were common enough; they were living all the while in other coral tracts. But the break between the Palæozoic and the Lower Cretaceous forms cannot be bridged over without investigating the value of the classification which separates the most closely allied subfamily of the Perforata, although the Perforata are found in the Great Oolite.
II. The Perforata characterized by a porous coenenchyma and other tissues present many modifications of their hard parts. Some approach the Aporosa, and others would hardly be considered corals by the uninitiated on account of the sponge-like reticulations of the skeleton. The genus Madrepora is defined as follows by MM. Milne-Edwards and Jules Haime :
The corallum is compound and increases by budding. The cœnenchyma is abundant, spongy, reticulate, slightly or not at all distinguishable from the walls, which are very porous. The visceral chambers are subdivided by two principal septa, which meet by their inner margins, and are more developed than the others.
The septa, especially the two largest, although perforated, are continuous, and very often lamellar.
MM. Milne-Edwards and Jules Haime distinguish the Poritidæ in the following manner :—
The corallum is compound, and entirely formed of a reticulate coenenchyma, which is formed of trabeculae and is porous. The corallites are fused together by their walls, or by an intermediate cœnenchyma, and they multiply by budding, which is usually extracalicular and submarginal.
The septal apparatus is always more or less distinct, but never completely lamellar, and is formed by a series of trabecula, which constitute by their union a sort of lattice-work. The walls present the same structure as the septa. The visceral chambers sometimes have rudimentary dissepiments, but are never divided by tabulæ.
This family is divided into two subfamilies
1. The Poritinæ, with a rudimentary or absent conenchyma. 2. The Montiporine, with a well-developed cœnenchyma.
It will be noticed, when specimens of Montiporine and Madreporæ are compared, that the distinction is in the absence of the two large and not very perforate septa in the case of the first-mentioned group, and it is clear that the excessively trabecular character of its septa, cœenenchyma, and walls is characteristic. Moreover the Montiporinæ are recent forms.
The genus Litharaa amongst the Poritinæ approaches Madrepora, however, and its septa are often so lamellar that they resemble those of some Heliastræans amongst the Aporosa. Here the distinction between the forms becomes limited. The two great septa are not extended to the median line in Litharæa, and there is scanty cœnenchyma, but still there is some. The columella of Litharæa is simply formed by the union of trabeculæ from the septal ends.
Now Protaraa vetusta, Hall, and Protarea Verneuili, Ed. & H., Lower Silurian corals from Ohio, only differ from the species of Litharca by having more aporose septa and some cœnenchymal protuberances. It is necessary, however, on account of the comparatively late appearance (so far as our investigations has as yet gone) of Madrepora and Litharca, whilst admitting the extraordinary relation of the last-named genus to Protaraa, to examine another of the Jurassic Perforata.
The genus Microsolena of the Poritinæ carries the excessively trabecular type of the Poritinæ as far back as the Great Oolite; it is of course one of the extreme forms, and most remote from Madrepora. It has more or less confluent septa, and nothing like the styliform columella of Protaraa. Thus Paleacis, a form of the Madreporinæ, and Protaræa, a type of the Poritinæ, are still unsatisfactorily disconnected by intermediate species with their allies in the secondary rocks. But, on the other hand, it is something to be able to show an anatomical connexion between the Protarea of the Lower Silurian and the Microsolena of the Jurassic and of the Litharaa of the Nummulitic rocks, and between Palaacis and the Turbinarians of the group Madrepora, of which Actinacis is the oldest (Lower Chalk)t. It shows that the reticulate or perforate corals existed amongst the first known coralliferous rocks, that the scheme of their organization has been perpetuated to the present day through many kinds of variations, but with a great break, which is owing to the imperfection of the geological record.
III. The Tabulata, which form such large portions of many modern reefs, were, as has been already noticed, in existence during the Miocene‡, the Oligocene §, and the Eocene. They were, of course, not found amongst the deep-sea deposits of the Cretaceous period, such, for instance, as our White Chalk; but Reuss found the genera in the reefs of Gosau. Heliopora Partschi, Reuss, sp.; H. macrostoma, Reuss, sp.; Polytremacis Blainvilleana'; P. bulbosa, d'Orb.: these are not uncommon in the reefs which were in relation with the Hippurites, and the last coral genus lived during the Eocene. Reuss established a genus in 1854 for some compound, massive corals, with prismatic corallites with thick imperforate walls. The calices are without radiating septa and have no columella. The tabulæ are very irregular, some being complete and others uniting obliquely with their neighbours. The septa are represented by trabeculæ. This Lower Cretaceous genus he named Stylophyllum, and will be considered further on.
* See Hist. Nat. des Corall. vol. iii. p. 185.
+ M. Lindström has lately described a Calocystis, a perforated coral from the Silurian.