Although there is no order of superposition to be seen, they must be divided into two parts, on account of the difference in the fauna of the different beds. The lower part contains a large number of species from the Système Tongrien and Système Rupélien, together with a number of new and very characteristic fossils-large Spatangides (Echinolampas Kleinii and others), Pecten, Cytherea, &c., which pass over to the superior part, where small Nassa make their first appearance, generally in large numbers. This genus does not exist in the older beds, but occurs generally in the rocks of the Miocene and Pliocene periods, and exists in the recent seas.

It is impossible at present to give comparative lists of fossils, because many of the species have not yet been described, or, if described, have been incorrectly determined; but no geologist who has studied these beds, as well as the underlying and overlying strata, can deny that they form, with the Systèmes Rupélien and Tongrien, a particular group, as different from the older as from the younger deposits. This fact has been fully recognized by Professor Beyrich, of Berlin, who proposed, many years ago, in a paper communicated to the Royal Academy of Berlin*, to establish for this group the name of Oligocene; and this name has been accepted wherever its upper member (Cassel, Osnabrück, &c.) is known. The London Clay and Lower London Tertiaries now form the Lower Eocene, the Bracklesham series the Middle, and the Barton Clay the Upper Eocenet. The Système Tongrien inférieur represents the Lower Oligocene, and the Système Rupélien the Middle Oligocene, to which it will be necessary, I suppose, to join the Belgian freshwater beds of the Système Tongrien supérieur.

The Lower Oligocene is well developed, with a true marine fauna, in Belgium, near Tongres (north of Liége), and in the North of Germany between Magdeburg, Bernburg, Aschersleben, Egeln, and Helmstädt (near Brunswick ‡), and it contains above 700 species of Mollusca, besides a large number of Corals, Bryozoa, and Foraminifera, and several species of Fish-teeth and Echinodermata; and the most characteristic of these fossils have also been found at Brockenhurst. The fossils from this locality contained in Mr. Edwards's cabinet are the following (the asterisks in the different columns signify the presence of the different species in the respective beds) :

:

* "Ueber den Zusammenhang der norddeutschen Tertiärbildungen, zur Erlaüterung einer geologische Uebersichtskarte." Abhandl. der K. Akad. der Wissenschaften zu Berlin. Aus dem Jahre 1855, p. 1.

The White Glasshouse-sand also belongs to this last division, because, at Hordwell, it contains many characteristic Barton fossils-Oliva Branderi, &c.

As these fossiliferous beds (about 10 feet in thickness) are covered with beds of gravel and sand, sometimes more than 200 feet thick, and containing much water, it is impossible to dig pits for the mere purpose of obtaining the fossils. But below these beds there are seams of fossil wood, upwards of 150 feet in thickness, which are worked by numerous mines, and to this circumstance we are indebted for obtaining the fossils, which are found in a tolerable state of preservation only at the different mining-works which pass through the fossiliferous beds.

Of these 56 species, 43 exist in the Lower Oligocene of Germany, and 6 are peculiar to the English Brockenhurst and Headon beds; 21 of them are found also in the Upper Eocene, and 4 pass over to the Middle Oligocene of Germany; 23 of these species are characteristic Lower Oligocene species, which have been met with neither in the older nor in the younger beds, therefore there can be no doubt that the Brockenhurst beds, and with them the Headon series at Colwell Bay and Whitecliff Bay, belong to the Lower Oligocene.

The Middle Oligocene occupies a very great surface of the Continent in France the "Sables de Fontainebleau" are well known; and the Mayence Basin is equally so, through the excellent work of Professor Sandberger. M. de Koninck many years ago, and M. Nyst more recently, have described the fossils of the Rupelmonde Clay of Belgium. The Rupelmonde Clay, or Clay with Septaria as it is called in Germany, is covered by the Upper Oligocene strata (yellow and green marls) round Cassel in Hesse, as Professor Beyrich has described in another paper read before the Royal Academy of Berlin*.

Proceeding eastward, we find numerous localities where MiddleOligocene beds occur, sometimes superposed to the Lower Oligocene, as in the neighbourhood of Brunswick, Magdeburg, Cöthen, Berlin, and Freienwalde in Mecklenburg, and, last of all, north of Stettin, where they consist of several hundred feet of yellow ferruginous sands, with occasional layers of dark "Septarien-Thon." Generally the Middle Oligocene is developed as a dark bluish clay, possessing then a true marine fauna identical with that of Rupelmonde (south of Antwerp), and containing Leda Deshayesii, Fusus multisulcatus, Nyst, and Pleurotoma as the most common fossils; this clay has always been considered as being the upper part of the Middle Oligocene, and is so in reality in Belgium, and generally in Germany.

In the Mayence Basin, the Rupelmonde Clay was discovered only a

* "Ueber die Stellung der Hessischen Tertiärbildungen." Bericht der K. Preuss. Akad. der Wissenschaften zu Berlin. Aus dem Jahre 1854, p. 640.

few years since by Mr. Weinkauff*; and Professor Sandberger considers the marine sand of Weinheim, &c., as the lower part, and the "clay with Septaria" as the upper part, of the Middle Oligocene, including all the freshwater beds in the Upper Oligocene. The marine sand of Weinheim he identifies with the "Sables de Fontainebleau" and some sandy beds at Neustadt-Magdeburg, and also with the upper (marine) beds of the Hempstead series. Now the fauna of the Neustadt-Magdeburg and Weinheim beds is somewhat different from that of the real "clay with Septaria" described by several authors, but in certain localities in the North of Germany, for instance near Söllingen (near Brunswick), beds with the same fauna as those near Magdeburg are seen in superposition to the clay with Leda Deshayesii. We are obliged, therefore, to consider the difference of these two faunas as caused only by a difference of conditions at the localities, difference in the depth of the sea, &c., indicated too by the difference of the lithological structure,―and for this reason we cannot divide, generally, the Middle Oligocene into two periods.

Mr. Edwards, whose complete knowledge of the English Tertiaries abundantly qualifies him for the task, intends working out the identity of the Mayence and Belgian freshwater fossils with those of the Isle of Wight, and I have no doubt that he will find, besides the great number already considered identical, a still greater number common to the three localities. The freshwater beds of the Mayence Basin and of Belgium will therefore probably form part of the Middle Oligocene, as well as all the Hempstead series. It will be decided only then, where we are to place the Bembridge series and, with it, the Paris freshwater beds, which until now have been considered to belong to the Lower Oligocene.

One of the best reasons for accepting Professor Beyrich's "Oligocene" is, I think, that between each of his four periods there appear to have been great general changes over all Europe. The marine beds of the Eocene period in France and England are mostly succeeded by freshwater beds; sometimes the Oligocene beds do not exist at all, whereas they are the lowest Tertiary strata over all Germany, from Brunswick to Königsbergt. Miocene formations do not exist in England and in the North of France; in Belgium ‡ and in Northern Germany they occur very near the coast; but, on the other hand, beds of this age are very much developed in Poland, Hungary, Southern Germany, and the South of France, where the Oligocene is wanting. The Pliocene, again, is wanting in the last-named countries and in the North of Germany, while it skirts the coast in Belgium and France, and occurs also in England. See his paper" Septarien-Thon im Mainzer Becken." Neues Jahrb. 1860, p. 177; also Ueber die tertiaren Ablagerungen im Kreise Kreuznach." Zeitschrift der nat.-hist. Vereins der Preuss. Rheinlande und Westphalens. Jahrg. xvi., p. 65.

+ Prof. Beyrich considers certain beds near Königsberg to be Lower Oligocene. About a twelvemonth ago I identified the Système Diestien of M. Dumont with the Miocene of the North of Germany. Typical species from the Superga near Turin, as Oliva Dufresnei, Bast., Nassa flexuosa, Brocchi, &c., exist there. The Système Bolderien is also identical with the Système Diestien.

2. On the LIASSIC STRATA of the NEIGHBOURHOOD of BELFAST. By RALPH TATE, Esq., F.G.S. With DESCRIPTIONS of NEW SPECIES of MOLLUSCA, &c.; by R. ETHERIDGE, Esq., F.G.S., F.R.S.E.

1. Introduction.

CONTENTS.

2. General Geological Description.
3. Zone of Avicula contorta.
4. Section at Whitehead.

5. Zone of the White Lias.

6. Zone of the Lower Lias.

7. Distribution of the Liassic Rocks in the North of Ireland.

Notes on Species.

1. Introduction.-General Portlock, in his Geological Report on Londonderry, Tyrone, and Fermanagh (1843), was the first to direct attention to certain beds linking the Triassic and Liassic formations. In that Report he refers to the occurrence of beds at Colin Glen, Belfast, characterized by the same Shell (Cardium striatulum) as that which occurs in the Lisnagrib section (pp. 49, 56, 107).

It is now my purpose to describe in detail the strata thus referred to, and their extension to neighbouring localities.

Within the last few years the stratigraphical relations and the fauna of the Lower Liassic and Avicula-contorta series, as developed in England, have been made known by the labours of Dr. Wright* and Mr. Charles Mooret.

I trust the value of the present communication is enhanced by the attention I have given to the correlation of the Belfast beds with the members of the same epoch, as detailed in papers read before this Society, and referred to above.

The following members of the Liassic period are developed in the neighbourhood of Belfast, namely, the zone of Ammonites Bucklandi, the zone of the White Lias, and the zone of Avicula contorta; but before proceeding to the details of these formations, I shall give a short description of the geological features of the locality, rendered somewhat necessary by the peculiarities that here occur.

2. General Geological Description.-The neighbourhood of Belfast is divided by the Belfast Lough and the River Lagan into two naturally well-marked sections, both as regards the geological formations and its geographical relations:-the Northern Section is part of the county of Antrim, and the geological formations are Neozoic; the Southern Section is situated in the county of Down, where the formations are Palæozoic.

The Northern Section is occupied by the Belfast Hills range, the basis of which is the Keuper formation, presenting a steep incline, rising from the shore and the River Lagan to a maximum elevation of 650 feet. The New Red is surmounted by the Lias, Gault, Upper Greensand, Hard Chalk, and Basalt; forming a bold escarpment extending from Whitehead on the north-east to Lisburn, &c., on the south-west, with an average elevation of 1000 feet. Numerous trapdykes intersect or cut through all the sedimentary rocks, and may be carried up into the overlying Basalt. The prevailing strike of the dykes varies between N.E. and N.W.

* See Quart. Journ. Geol. Soc. vol. xvi. p. 374, &c. + Ibid. vol. xvii. p. 483, &c.