extent of surface, to their concordant and uninterrupte superposition, it is possible to arrive at an absolute certaint as to the duration of species, that is to say, the point in th series where they first appear, and where they become extinc

In order to compare North America with Europe, it ha been necessary for us to give a rapid glance at the group and stages of which the paleozoic class is there composed The differences which are presented to us in the geognosti conditions of the state of New York, and the Wester States, such as Ohio and Indiana, have revealed to us the degree of importance which it is necessary to attach to thes different groups. We have seen that their number, variable according to their vicinity or distance from lands emerged at the epoch of their formation, had little importance, as regards the establishment of systems founded upon palæontological characters. We have seen also, that in general the limestones are more constant than the shaly or arenaceous beds, that they form more extensive horizons, and furnish a surer guide to the geologist.*

Passing afterwards to a comparison of the two continents, we have shewn, supporting our views by geological analysis, how the American sub-stages should be grouped to correspond with the Silurian, Devonian, and Carboniferous systems of Europe. We have not disguised the fact, that the divisions introduced upon this principle did not correspond, in certain countries, with the divisions indicated by the mineralogical character of the rocks; thus the limit between the two stages of the Silurian system, very well marked in the state of New York, is observed near the Mississippi, in consequence of the predominance of magnesian limestone; it is the same with the Silurian and Devonian systems, the limit between which is found in the upper part of the great calcareous formation called cliff-limestone; as well also as with the carboniferous system, in parts of the state of Ohio, where it is in contact with the Devonian psammites of Portage.

*M. C. Prevost, in his Memoir upon the Synchronism of Formations (Comptes Rendus, April 1845), has clearly shewn the importance of the pelagic calcareous deposits, as compared with the arenaceous beds formed under the influences of coasts.

These mineralogical transitions, which one would expect in a country free from disturbances, would not, however, obscure the proofs of a parallel development of the animal kingdom in the two continents; for if, leaving aside the difficulties of fixing the limits between the systems, we compare the systems together, or, still better, one by one the groups of which they are composed, we acquire the conviction that identical species have lived at the same epoch in America and in Europe, that they have had nearly the same duration, and that they succeeded each other in the same order. We have endeavoured to prove that the first traces of organic life in countries the most remote, appear under forms nearly alike, at the base of the Silurian system, and that the same types, often the same species, are successively, and in parallel order, developed through the entire series of the paleozoic beds. If we have not succeeded in lifting the veil which still hides from us the cause of this grand phenomenon, perhaps at least our observations demonstrate the insufficiency of those causes by which certain authors seek to explain it. They prove, in effect, that the phenomenon itself is independent of the influences which the depth of seas* exercise upon the distribution of animals; for if, in certain countries, the Silurian deposits prove a deep sea, they have, on the contrary, in the state of New York, a littoral character. They prove, in fine, that in its general character it is equally independent of the upheavings which have affected the surface of the globe; for, from the eastern frontier of Russia even to Missouri, distant from or near the lines of dislocation, in the horizontal beds, as well as in those which are disturbed, the law according to which it is accomplished appears to be uniform.—(The American Journal of Science and Arts, vol. vii., p. 48.)

* We do not pretend to say that the differences of depth in the seas had not already an influence upon the distribution of animals; it is to this circumstance, on the contrary, that we attribute the more or less local fauna which we often discover in the paleozoic class. But these local fauna always afford some species which connect them with the epoch to which they belong. They are the exceptions (hors d'œuvre), which do not derange the general symmetry.

1. Flora of the Silurian System. 2. Plants of the Anthracite Formation of Savoy. 3. Fossil Plants, as illustrative of Geological Climate. 4. Co-existence of Certain Saurian and Molluscous Forms at Equal Geological Times. Phosphate of Lime in the Mineral Kingdom.*

5.

1. The Flora of the Silurian System.—In a memoir on the geology of the neighbourhood of Oporto, including the Silurian coal of Vallongo, Mr Sharpe furnished us with a detailed account of a part of Portugal, of which, in 1832, he presented a brief notice to this Society. After mention of the crystalline rocks near Oporto, his section shewing the granite of Oporto, covered on the WSW. and ENE. by gneiss, mica slate, and chlorite slate, he describes a band of rocks, chiefly formed of clay-slates, resting upon the eastern flank of the latter, and which, from the character of the organic remains obtained from it, he refers to the Lower Silurian deposits. The lowest part of this series is remarkable for containing several beds of anthracite, worked at San Pedro da Cora, eight miles ENE. from Oporto. Mr Sharpe states that the section is clear, and that these lower beds, which repose on chlorite slate, evidently dip beneath deposits containing Lower Silurian fossils. The upper part of the group is formed of a thick accumulation of micaceous sandstone, usually yellow, with some grey carbonaceous sandstone near the bottom. This rests on a black carbonaceous slate, among which are bands of indurated ferruginous clay, passing into clay ironstone. Beneath this comes a dark grey or black hard clay-slate, with softer chloritic beds of a pink or yellow colour in the lower part. Notwithstanding its contortion, this slate series is considered to have considerable thickness. The lower beds of the dark grey slates, and those lighter coloured and softer at the base of the series, are rich in organic remains (Calymene, Ogygia, Isotelus, Illænus, Chirurus, Beyrichia, Orthis, Orthoceras, Bellerophon, Graptolithus, and others), possessing a character from which Mr Sharpe refers these deposits to the Lower Silurian period.

Beneath these strata, in descending order, the carboniferous accumulations of San Pedro da Cora occur, gradually passing into the beds above them. These carboniferous beds consist in descending order of (a) red sandstone, (b) coarse conglomerates alternating with black carbonaceous shales, (c) coal, 6 feet thick, (d) coarse micaceous conglomerate, alternating with black carbonaceous shales, (e) coal, thin bed, (f) coarse carbonaceous conglomerate, (g) coal, four beds, from 2 to 5 feet thick, variable however in thickness in different places, the beds separated from each other by 3 or 4 feet of black

*The interesting details and views in this article we owe to Sir Henry de la Beche's valuable Anniversary Address for 1849 to the Geological Society, a copy of which was forwarded to us by the Author.

shale, and resting on black shale, and (h) slates apparently composed of the debris of the chloritic schists on which they rest. The carbonaceous series is estimated at from 1000 to 1500 feet thick, and is seen on the north bank of the Douro, at Jeremunde, twelve miles from Oporto. North of San Pedro da Cora this series rapidly thins away, and disappears about a mile and a half from that place.

Having given a detailed account of the rocks referable to the Silurian series, noticed by him in Portugal, Mr Sharpe refers to the beds described by Dr Rebello de Carvalha as forming the chain of the Serra de Marao, near Amarante; those mentioned by M. Schulz on the eastern side of Gallicia, by Link in the province of Tres os Montes, and by Le Play in Spanish Estremadura, and infers that these also may belong to the Silurian series.

The lithological characters of the carboniferous deposit of Vallongo, thus plunging beneath beds containing organic remains referred to the date of the Lower Silurian deposits, are important, as shewing the physical conditions under which the accumulations have been effected, and their general agreement with many other deposits, in which sheets of vegetable matter have been so formed, as eventually to have been turned into coal and anthracite, amid mud charged with carbonaceous matter and beds of shingles. Why we should not expect accumulations of the kind at this period, the fitting conditions for the gathering together of plants or their remains, either by growth on the spot or drift from their place of growth, so that they were mixed with little or no common mud or other sedimentary matter, does not appear. We find old mud accumulations, now forming black slates, common enough in some parts of the Silurian series, and there is no want of carbonaceous matter in the black slates of North Wales and Ireland beneath the whole mass of the beds commonly referred to that series.

The occurrence of the anthracite beds in the position and under the conditions stated by Mr Sharpe, would be highly interesting in itself, as shewing to what extent clean or nearly clean accumulations of vegetable matter may have been effected amid deposits in which the carbonaceous, and, we may fairly conclude, vegetable matter was generally more diffused amid mud and gravel; but the remains of fossil plants detected in connection with this carbonaceous series are still more interesting, always assuming that the sections seen by Mr Sharpe are unequivocal, as his certainly would appear to be, unless we suppose a most enormous reversal of these deposits.

The remains of the plants found by Mr Sharpe were submitted to the examination of our Foreign Secretary, Mr Bunbury, who, though the specimens of ferns were in bad preservation, considered that one bore a strong resemblance to Pecopteris Cyathea, of the coal-measures; another reminded him of Pecopteris muricata, and a third of Neuropteris tenuifolia. Mr Sharpe calls attention to the evidence, as far as it goes, afforded by these plants, of a vegetation

having existed similar to that of the coal-measures at a geological date long anterior to them. It would indeed be of the greatest geological importance to arrive at an insight into the kind of vegetation that clothed the land, which furnished by its disintegration, abrasion, and removal, by river and breaker action, into fitting places of deposit, those thick accumulations now known as the Silurian series. We appear to have fair reason for concluding that, while the seas swarmed with trilobites and molluscs, the dry land, supplying the detritus amid which these remains were entombed, was not a desert waste, a mere mass of rocks decomposing under the action of the atmosphere, and worn away along the sea-level by the breakers; in fact, nothing but a storehouse for the production of the marine sediments of the time. We require a marine vegetation as a base for the existence of the sea animal life of the period; and we may fairly infer no lack of terrestrial vegetation flourishing beneath the atmosphere at the same time. What that vegetation may have been we have yet to learn; but as the range of the Silurian deposits becomes more known over the earth's surface, in regions where they have either never been covered by more modern deposits, or having been so covered, are now bared by denudation,—and every day we learn more and more of their distribution,—we may expect to obtain a better insight into the kind of plants existing at that remote geological period.

2. Plants of the Anthracite Formation of Savoy.-Among the labours of our Foreign Secretary, Mr Bunbury, during his late travels on the continent, was included an examination of the fossil plants from the anthracite formation of the Savoy Alps. The results of this investigation he communicated to us in a memoir, in which he not only describes the species of plants that came under his observation, but also gave us a history of the researches and opinions connected with the mode of occurrence of these plants, adding general views of his own.

As you are aware, M. Elie de Beaumont was the first, in 1828, to announce the fact, that near Petit Cœur in the Tarentaise, beds containing an abundance of plants, of the same species as those discovered in the coal-measures of the paleozoic period, alternated with other beds containing belemnites, and referred the whole to the period of the lias. The plants were determined by M. Adolphe Brongniart. Subsequently M. Elie de Beaumont published an account of beds occurring between Briançon and St Jeane de Maurienne, and included them in the same series. Plants obtained from these rocks were examined by M. Adolphe Brongniart, and identified by him with those of the coal-measures. From all the facts, M. Elie de Beaumont inferred that the beds with belemnites and ammonites, and those containing the plants, were parts of one whole, and that whole referable to the date of the lias and part of the oolitic series. This announcement was startling to those who were accustomed to