The discussion on Mr. Boyd Dawkins's paper, “ On the age of the Lower Brick-earths of the Thames valley,” at the meeting of the Geological Society of London, 9th of January, induces me to submit a view of the relative ages of the Boulder-clays of the east of England, which seems to bring into harmony the views of Mr. Dawkins, and the physical evidence suggested in the discussion that seemed to conflict with them.

Mr. Dawkins' opinion that the lower deposits of Brick-earth at Grays' Thurrock, Crayford, and Erith were super-imposed by a Glacial deposit containing transported materials, was objected to on the grounds that they occur in a valley apparently excavated after the deposition of the Boulder-clay capping the high land to the north of London—implying an interval between the Muswell Hill Boulder-clay, and the supposed Glacial deposits of the Thames Valley, represented by the entire excavation of the valley, and the deposition of the Brick-earths and gravels, containing mammalian remains, underlying the Glacial beds.

One of the characteristic features of the warmer and intertropical regions of the globe, is the presence in abundance of those highest forms of Crustacea, the Shore- and Land-crabs.

The object of the following paper is to record some further observations on the distribution in North Wales of deposits of White Clays and Sands older than the Boulder-clay and its accompanying gravel drifts, similar to those in the neighbourhood of Llandudno, described in the Geological Magazine of May, 1865, and also to give a condensed summary of what records I have been able to collect of the occurrence of similar deposits in other parts of the kingdom.

Anyone accustomed to the peculiar outlines which ancient ice action has produced in the Alps, cannot fail to be struck, at the first glance, by the contours to the upper parts of the Great Ormeshead and of the Carboniferous Limestone range which extends from near the village of Rhos to the Little Ormeshead; and a more minute examination only strengthens the conviction that, while the leading outlines of the hills are due somewhat to upheaval, but mainly to denudation—probably marine, the surface of the higher ground has in many cases been affected by ice.

Among the metamorphic phenomena which seem to me deserving of more attention than they have yet received, I have been especially interested by those existing in the brecciate formations. They are, of course, in the main, two-fold; namely, the changes of fragmentary or rolled-pebble deposits into solid rocks, and of solid rocks, vice versa, into brecciate or gravel-like conditions. It is certainly difficult, in some cases, to discern by which of these processes a given breccia has been produced; and it is difficult, in many cases, to explain how certain conditions ofbreccia can have been produced either way. Even the pudding-stones of simplest aspect (as the common Molasse-nagelfluhe ofnorth Switzerland) present most singular conditions of cleavage and secretion, under metamorphic action; the more altered transitional breccias, such as those of Valorsine, conceal their modes of change in a deep obscurity: but the greatest mystery of all attaches to the alterations of massive limestone which have produced the brecciated, or apparently brecciated, marbles: and to the parallel changes, on a smaller scale, exhibited by brecciated agate and flint.

In connection with the preparation of the second edition of “Acadian Geology,” I have obtained, from friends who have been engaged in geological investigations in Nova Scotia and New Brunswick, some interesting illustrations of the entomology of the Carboniferous and Devonian Periods, which I have thought it might be useful to publish in advance of the appearence of my work.

As confirmatory of the Miocene age assigned by me, on other palæontological grounds, to the Tertiary sands on the Southern shores of Victoria, containing the Trigonia semiundulata (M'Coy), I think the accompanying figure (Plate VIII., Fig. 1), of the natural size, of a molar of an Australian species of the mammalian genus Squalodon, may be of interest.

The species is smaller than any of the American Eocene Zeuglodonts, or the Maltese Miocene Squalodon Melitensis, and it differs form them all in the great proportions, length (or depth), and imperfect bifurcation of the root. In the latter, and all other characters, it most nearly agrees with the Squalodon Grateloupi of von Meyer, from the French Miocene beds near Bordeaux.

The study of the crystalline and metamorphic rocks seems hitherto to have been rather avoided by British geologists, who have more exclusively devoted their attention to the stratified and fossiliferous deposits, and left this field of research all but entirely to be cultivated by their continental brethren.

The district known as the Wealdmoors of Salop is an ancient lake-basin about seven miles in length, by four in width. It lies east of the Wrekin, from which the ground slopes gradually down to it. On the S.E., the high ground of Lilleshall, and its vicinity, rises more abruptly, and on the N.E. extremity it is intersected by the river Tern, which probably formed the principal outlet. The centre of the basin is filled with peat, containing remians of oak and hazel trees, very much decayed, and matted together by thick layers of fibrous roots, and in the lower part, by a species of moss, of which the fibre is too fine for the Sphagnum, but which it is impossible to identify, on account of its decayed condition. This peat attains a thickness of about six feet. Some years ago, a bronze celt of fine workmanship, and which is considered to have been manufactured since the commencement of the iron age, was found imbedded in it.

There are some points in Mr. Maw's article on the relative ages of the Boulder-clays which require notice from me, because they involve the consequence of assigning to the deposit which I have described under the name of “trail” an antiquity far higher than that which I believe to belong to it.

I wrote the first of these papers more with a view of obtaining some help in my own work than with any purpose of carrying forward the discussion of the subject myself. But no help having been given me, I must proceed cautiously alone, and arrange the order of my questions; since, when I have done my best as carefully as I can, the papers will be nothing but a series of suggestions for others to pursue at their pleasure.

It will, no doubt, be admitted by all, that it is highly conducive to the advancement of any science, that some one of its votaries, more courageous than his colleagues, and endowed with a more generalizing turn of mind, shall, by the comprehensive and exact study of accumulating observations, endeavour to elevate himself above the level of the more plodding but invaluable collectors of facts, by attempting the arrangement and organization of such data, and the deduction therefrom of the laws which regulate their existence and govern their movements.

The extinct cartilaginous fishes represented in ‘mountain lime-stone’ and similary aged carboniferous formations by detached teeth, or dental masses adapted for crushing, have been referred to the Cestraciont family; and, so far as I know, have now no nearer living representative, in the class of fishes, than the Port Jackson shark (Cestracion Philippi.)

On the genus Necrosius.—This new genus is very near to Ozius, and is still more near to a small genus, established a few years since by M. Stimpson, named Spherozius. Like this last-named form, the carapace of Necrozius is remarkable for its globular form, its width scarcely surpassing its length. The curve of the buckler is slight in a transverse direction, but is great from back to front, the anterior border being much curved down. The latero-anterior borders are continuous, almost without interruption, with the latero-posterior, which latter are swollen. The frontal border (rostrum) projects a little, and is slightly depressed in the centre. The basal joint of the internal antennæ is large, and it is articulated obliquely beneath the front (rostrum). The basal joint of the external antennæ is short, not reaching to the front as in the Pseudozius of Dana, and in spherozius of Stimpson; the articulation is free and is not lodged in the internal obital cavity. With Ozius on the contrary, this basal joint is fully attached to the front.

I obtained, the other day, on my way into South Devon, another peep at the Bristol Channel, and the gorge of the Avon, at Clifton, which I had long been wishing for. It showed me, as I anticipated, that the hypothesis of atmospheric erosion, which I was compelled to adopt, a year or two ago, to explain the formation of the river valleys of the South of Ireland, is applicable to the Clifton gorge as to all other similar places.

Two of the Gymnospermatous Orders are represented by fruits found in Secondary strata, viz., Cycadeœ and Coniferœ; no remains have been observed, as far as I know of any plant belonging to the Gnetaceœ.. There is satisfactory evidence of the existence of Coniferœ from the period of the Old Red Sandstone; but it is very doubtful whether the Palæozoic fruits and leaves which have been referred to Cycadeœ have anything whatever to do with that order.

Among the many singular discoveries made in the ruins of Pompeii, and deposited in that most interesting of Museums, the Museo Borbonico, in the city of Naples, are a variety of shells, principally species now found in the Mediterranean Sea, and so far of interest as an illustration of the persistency of certain known species within the historic period, no difference whatever being observable between the disinterred and living specimens. On a close examination I observed, besides those from the neighbouring seas, species from distant countries, for example:—Conus textilis, Triton femorale, Meleagrina margaritifera (Pearl Oyster), species only found in the Indian and Eastern seas. I think, therefore, that this may be regarded as part of a Natural History collection. Assuming the truth of this conjecture, its antiquity is without a precedent. Did the original proprietor form one of a Natural History Society of Pompeii, of which the distinguished Naturalist Pliny, who perished at Pompeii, was a member? It would also be curious, in these days of research for priority of names, to know how they were described. Such a discovery might disturb existing nomenclature, and increase the perplexity already felt in naming collections. But laying aside fanciful conjectures, the collection is further instructive from the condition and perfect preservation in which the specimens are found, after an interment of nearly 1,800 years. Besides the collection in the Museo Borbonico, there is still standing in a villa at Pompeii, a fountain decorated with shells of the Mediterranean, one species of which, viz. Murex Brandaris, retains its colour and general freshness and is not to be distinguished from living examples; while the same species, from the Italian Tertiaries, are colourless and in that friable condition characteristic of shells even of the most recent geological period, pointing, like other discoveries, to the great antiquity of the most modern Tertiary deposits as compared with the era of the human race.

When examining the collections of the Geological Society at the time of preparing the notes I published some months ago, on the Fossil Cones of the Secondary Strata, I found a small fragment of a curious vegetable organism, the nature of which I was then unable to determine, but which I was allowed by the kindness of the Secretary to take with me for the purpose of further examination. Some months ago I obtained from James Yates, Esq., a more perfect specimen, which clearly showed that it was the portion of the stem of a cycadean plant, as Mr. Yates had already determined. Professor Church subsequently brought me a yet finer specimen from the Museum of the Royal Agricultural College at Cirencester, and I have a fourth fragment from the collection of Professor Morris.

As the remains of insects are rarely found in Carboniferous strata, a short account of three imperfect specimens, which have been discovered in the Durham coal-field, may not be deemed valueless. Indeed, with the exceptions of the specimens described from Coal-brook Dale by Prestwich, twenty-five years ago, and the examples of Xylobius sigillariœ of Dawson,—discovered by Mr. Tindall, in the Lower Coal Measures, near Huddersfield, and by Mr. Thomas Brown, of Stewarton, in the Upper Coal Measures of Kilmaurs,—I am not aware of any other fossils of this class having been noticed as occuring in Carboniferous rocks in England.

The consideration of the subject of Denudation requires so extensive an acquaintance with Forms of the Ground in a field large enough to embrace all countries, that general conclusions must be advanced with more or less reserve, in proportion to the extent of our research.