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diverge a little, and on doing so we find ourselves in the presence of rocks that are called Devonian, consisting principally of reddish-coloured limestones, slates, and shales, such as are found in the neighbourhood of Torquay and North Devon, and which extend into Cornwall. This is the Devonian strata, and below the Devonian we still pursue our way, across country, right into Wales, where we find a vast heaping up of mountain chains and other formations which are known as the Silurian, all still sloping inwards. Below these, again, we have an even grander mass of rocks called the Cambrian, and, dispersed amidst these, both, the Silurian and the Cambrian, exhibit also volcanic matter. The interpretation of this state of things must, of course, be, that each of these formations (proceeding westward), is beneath the other. I shall have to deal with four of these groups particularly, and, consequently, I have left out the minor layers, or strata, as not having anything to do with the subject of this paper. This brings me to that which I have put before you in the form of printed matter, and here I have to begin in a backward direction from that in which we have already travelled from London. We begin in fact where we just now left off, namely with the great Cambrian rocks :

PEDIGREE OF THE CORAL-REETS OF ENGLAND.

By S. R. PATTISON, F.G.S.

We propose to refer to the principal reefs of fossil coral

lessons they teach on the subject of Evolution.

CAMBRIAN ROCKS.

The fine hilly district which stretches from the Irish Channel to the hills of the Welsh border, is principally composed of coarse slaty rocks, which were named Cambrian by the veteran geological chieftain, Professor Sedgwick. In these we find a few fossil corals, and abundant remains of creatures classed by naturalists as Hydroids and Bryozoa (or moss animals), but no reef builders.

These Hydroids are the lowest corals, and Bryozoa are the lowest tribe of Molluscs. The former are lower by one step than the corals proper, and are so numerous in some of the Cambrian strata that whole floors and beds of limestone have resulted from their decay, although the creatures are individually extremely minute (Graptolites). They are of the same class as the true corals; yet no one who

observes the structure of both could for a moment consider the one as the progenitor of the other.

SILURIANS.

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Travelling thence eastwards, and passing the great volcanic region of Snowdonia, we find ourselves in a mountainous country of slate and sandstone, which was the theatre of the wanderings and wars of the ancient Silures, who contested the Roman advance. Sir Roderick Murchison, the explorer of this district, named the prevalent system of rock here, Silurian, and the appellation, having been found convenient, has been applied to rocks of the same kind all over the world.

Extending our journey towards Shrewsbury, through Wenlock, the traveller has by his side, for about thirty miles, a ridge of hills remarkably uniform, showing, wherever opened, limestone rock. On visiting any one of the numerous quarries on this hillside, the limestone is seen to be principally composed of rough blocks of fossil coral, embedded in shale and limestone. A very short study convinces the beholder that he is on a coral-reef of the old ocean, and that its growth and aspect must have been altogether like the description given of the great live reefs now existing in the Pacific Ocean. There are 102 specimens of corals in these strata, of which the more numerous belong to the genera Favosites (honeycomb coral), and Halysites (sea-stone, of which the chain-coral is well known), Monticulipora (little-mound pores), and Syringopora (pipe-pores). All these forms are absolutely unknown to any preceding platform of life in the geological scale ; they burst at once on the stage. There are no traces of direct ancestors, nor shall we find, as we ascend, that they leave any successors displaying their exact form and fashion.

Many genera of creatures are the same as in the succeeding rocks; but not one species. We can, however, perceive at a glance, that the old corals were as large, beautiful, and elaborate as any of the modern ones.

Whence came these curious creatures, or rather tribes? Were they emigrants ? There is no evidence of this. tbey descendants of any previous form? The facts forbid the assumption. Like Minerva springing from the head of Jupiter, they rise up fully armed cap à pied.

Were

DEVONIANS.

Diverging southwards on our journey–or, rather voyage across ancient oceans we come to the rich marbled rocks cut

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through by the South Devon Railway. These are seen in the ascent westward from Newton Abbot; and, spreading out, they form the exquisite bay of Babbicombe and the headlands and heights of Torquay. They display great beds of coralline stone, which furnish the workers of the district with beautifully-veined “Devonshire Marble."

There are found here about fifty-two specimens of corals, and they all exclusively belong to this epoch of life; not one of them is to be seen in the preceding Silurian, and not one of them passes into the subsequent Carboniferous

strata.

MOUNTAIN-LIMESTONE REEFS.

Again setting sail, we soon arrive at another reef. It might reasonably have been expected that the shallow islands on which grew the tropical vegetation now forming our coal-beds would be accompanied seaward by corals, which would assimilate them to the islands of the Northern Pacific. This is the case. Thus we have an interrupted reef extending from Somersetshire to Northumberland, along the line of which coralline strata are inter-stratified with shales (compressed mud), and grits (compressed sand).

The common corals of the great coal-limestone are Lithostrotion, Lithodendron, Syringopora, Lonsdalia, Zaplurentis, and Cyathophyllum. There are altogether in the British area one hundred and forty-four species of Carboniferous limestone corals, not one of which reappears in the next overlying formation, nor in any other.

JURASSIC REEFS.

Our next stopping-place will be on the yellow Bath buildingstone, extending from Whitby to Weymouth. The geological formation is called the Oolite (its grains being similar in shape to small eggs or roe), or the Jurassic, from its prevalence in the Jura Mountains. It is a series of sandbanks, now converted into freestone; mud, now turned into shale; and limestone, due principally to shells, and sometimes corals. In many places along the line it is evident that these former sandbanks were anciently crowned with coral formations.

These are so prevalent in one entire series that the rock is named the Corallian.

Mr. Etheridge enumerates not less than two hundred and thirty-six species of coral which have left their marks in the Jurassic rocks of England.

CRETACEOUS CORALS.

We will very briefly refer to these. In the English chalk there are several small corals, mostly of single growth. In the sandy commons between the Great Western line and the town of Faringdon, in Berkshire, there are very numerous small excavations, which disclose beds of exquisite sponges and Polyzoa, but no corals. On the summit of Haldon, in South Devon, are remains of a small coral-reef in the Lower Greensand.

There are seventy-six species of corals enumerated from the Cretaceous strata, not reef-builders.

TERTIARY CORALS.

Still higher up, or more recent, in the early part of the Tertiary period, vast coral-reefs are found, of which the remains are now visible in Central and Southern Europe, in Egypt, Syria, Arabia, and parts of India. In our own island we find in the Suffolk Crag numerous beautiful Polyzoa, some sponges, and but very few corals, and those only of the single kinds.

Now, having given a cursory sketch of the dwelling-places, we must glance at the dwellers.

The coral-animal may be described as a tiny sea-anemone, which secretes within itself a stony cell having upright partitions. The building rises up as it grows, and when the creature dies, the little cell and its ribs become visible. In one group of corals, called tabulate corals, there are horizontal plates as well as vertical; in the other there are vertical plates only. The latter group is called Rugose, or wrinkled corals. The little Polyps (as the animals are called), are of several kinds; many have a tendency to live together in colonies. In the live coral we find only a small bag of animated substance open at the top, but more or less closed at'the lower end. The inside of this bag has the power or property, by vital chemistry, of extricating and fixing grains of carbonate of lime from sea-water.

The reef-corals comprise :
1. All the Star-corals (Astrceido).
2. All the Mushroom-corals (Fungacia).
3. Certain of the Eye-corals (Oculinidae).

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4. Some of the Flower-corals (Cyathophyllido). 5. Madrepores, Brain-stones, and Free corals.

Among those genera which characterise successive rockformations are the following:

.

Lower Silurian { Heliolites, &c.

Upper Silurian

Devonian

Halysites, Favosites.
Monticulipora, Aulopora.
Syringopora, &c.
Cyathophyllum, Heliophyllum.
Acervularia.
Strombodes, Stromatopora.
Favosites, &c.
Lithostrotion, Lonsdalia.
Cyathophyllum.
Amplexus, Syringopora.
Montlivaltia, Astræa, Isastra.
Theosmilia, Thamnastræa.
Parasmelia, Syndelia, Stephanophyllia.
Cup-corals.
Cup-corals.*

Carboniferous

Jurrassic
Coralline Oolite

Cretaceous

Eocene

Pliocene

LESSONS OF THE REEFS.

Have the corals anything to say on the subject of Evolution,--the great natural history question of the present day? Do they show by their structures that they were evolved from previous forms, that they changed with the ages in conformity with law, or must we say to those who thus express themselves,

There are more things in heaven and earth, Horatio,

Than are dreamt of in your philosophy"} Regarding their succession, do we find the survival of the fittest, or proof of the change of one form into another by slow modification under the action of their surroundings ? Surely they can tell us something about these matters; they have lived long, and passed through many revolutions, their features are fine enough to preserve traces of all the vicis. situdes to which they have been subjected, and their forms are as definite as geometry itself. Our conviction is that

* For full information see the works of the accomplished leaders in this department, Professor Duncan, Dr. Nicholson, and Mr. Tomes ; and Mr. Etheridge's volume of Phillips's Geology.

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