The sands which are the subject of this investigation were taken from various parts of the Wealden area, and from different horizons, though all, except the French ones, are below the Weald Clay and represent the lowest division of the Cretaceous rocks, that is, the Hastings Beds.

One of us has been engaged for some years in the study of the Pleistocene gravels and associated deposits of the Cambridge district, and eventually proposes to give a full account of the results obtained. Meanwhile, considering the importance of noting the conditions under which Pleistocene floras are preserved, in order to draw attention to their probable occurrence under similar conditions elsewhere, it is thought advisable to give a preliminary account of the discovery of an Arctic flora of this date in a pit at Barnwell, a suburb of Cambridge, long noted for its Pleistocene deposits.

The peculiar features presented by the upper or land-surface portions of some deposits, or rather those portions of certain deposits which are now, or have been in times past, land-surfaces, have engaged the attention of many geologists. Most of those who have studied them are satisfied that some features which they often show are not now being produced in this country, and they are attributed by many observers to the action of different climatic conditions to those which at present exist.

Quenstedt described three distinct varieties of Ammonites Davœi, with nine illustrations. They all belonged to the 7 zone of Lower Lias:—

1. Ammonites Davœi, whose tubercles are somewhat clavate and with unsymmetrical prorsiradiate ribs.

2. A. Davœi enodis is continental. It is a small specimen without tubercles, with fine symmetrical and prorsiradiate ribs.

3. A. Davœi nodosissimus is also continental. This variety shows nine large bullate tubercles on each whorl, with close, fine, and symmetrically disposed flexiradiate ribs.

In continuation of the preceding paper (Geol. Mag., April, p. 156) which, as a preliminary to the present one, outlined the new classification of the crystalline rock formations and the nomenclature of the pietre verdi of the Piémontese Alps, I now propose to briefly describe the principal pietre verdi areas with which I became familiar during a long stay on repeated occasions in Turin. This city, apart from its rich collections of the rocks and minerals of the Piémontese Alps, is a most central and convenient starting-point for examining the different valleys debouching into the plain of the Po from the magnificent crescent formed by the Maritime, Cottian, Grajan, and Penniue Alps, which, as seen from Turin, afford by far the most extensive and fascinating Alpine panorama in Italy.

In a paper on the Permian formation in the Maritime Alps, etc. (Geol.Mag., 1916, pp. 7–17), I mentioned incidentally that it extends from those Alps, viz. from the Montgioie range east into Liguria as far as the Savona Hills. As in the former so also in the latter region, that formation is composed of essentially gneissic schists known as apenninites or besimaudites belonging to the Lower Permian or Permo-Carboniferous, and of sericitic schists, quartzites, and clastic rocks or ‘anagenites’ which constitute the Upper Permian or Verrucano proper, forming a transition to the Lower Trias. The geological limit of the Permian in the Savona Hills coincides more or less with the geographical line of division of the Alps and Apennines at the Colle or saddle—also called Bocchetta—d'Altare; but another geological line of division exists still further east, at the junction of the Triassic and Eocene formations in the Chiaravagna Valley near Sestri Ponente, immediately west of Genoa. In reality the geological division is marked, not by either of those lines but by a contact-zone between them. This contact-zone occupies the whole of Western Liguria and comprises two distinct and dissimilar parts: one, the Triassic calc-schists and pietre verdi area or Voltri group, which extends for about 25 kilometres along the Riviera littoral west of Genoa from Sestri Ponente to Voltri, Varazze, and Celle Ligure, and the other or Savona group, which skirts the littoral for about 15 kilometres from Celle to Savona and Zinola, and is composed for the greater part of a crystalline massif of granitic, gneissic, and amphibolic rocks.

The observations presented by Mr. J. Wilfrid Jackson (1916) on my paper on “Brachiopod Morphology”, published in this Magazine in 1915, are very welcome as furnishing many important details omitted by Davidson and other writers in the description of species. The error into which I fell as regards the types of folding of Dallina and Dalinella illustrates the danger of relying on figures when specimens are not available, but it was worth while making such an error when the correction of it brought forward so many useful observations on other points, particularly on the prevalence of dental plates in the Dallininæ and the relationships of Mühlfeldtia. These observations pave the way for a further advance in the natural or genetic grouping of species and genera. At the same time, while admitting that Dallina is ventrally biplicate, I am not disposed to agree with Mr. Jackson that the folding is exactly comparable to the ventral biplication exhibited in some species of Magellania, but probably arose in a different way. I refrain from a further statement on this point, as I understand that Mr. S. S. Buckman is discussing the subject of types of folding fully in his forthcoming memoir on the Jurassic Brachiopods of Burma. In what follows I shall have again, through lack of specimens in Colonial museums, to rely on figures to some extent, and may possibly again err from this cause, and if so hope the correction will be applied as promptly and informatively as in the former case.

Remains of Echinoderms are so rare in the Hartwell Clay of Buckinghamshire, and when found so fragmentary, that it may be worth while drawing attention to a small piece of an Echinoid test recently obtained from the Hartwell Brick-pit by Mr. Edwin Hollis, F.Z.S., curator of the Aylesbury Museum, and presented by him to the national collection (Brit. Mus., Geol. Dept., E 12241). The terminology of the following description is that defined on pages 59–65 of my “Triassic Echinoderms of Bakony”, Budapest, 1909.

In the course of a visit to North Wales last summer my friend Mr. Ivor E. Davies, of Penmaenmawr, called my attention to a mauve mineral, forming thin veins, in the intrusive porphyrite of Penmaenmawr Mountain. The specimens containing the veins were not seen in place, but were collected from the waste-heaps of the Graig Lwyd Quarries, the most easterly of the large quarries that are making such deadly inroads into the heart of the mountain. Careful search on the waste-heaps enabled us to collect further specimens, and in some of these the mineral had built in fissures and cracks somewhat crowded, very sharp-edged crystals of tabular development.

Sedimentary rocks show a variety of minor structures whose origin has been obscure. Among these are the small circular pits and mounds which sometimes mark the surfaces of sedimentary strata. Such of these as cannot be referred to rain-prints or the work of worms are apt to be referred by the geologist to some obscure type of concretion.

About one mile to the north of the railway station at Ayer Kuning, in the south of Negri Sembilan, one of the Federated Malay States bordering on Johore and Malacca, is a low but conspicuous range of hills covered with long grass. The highest of the hills, on which is a beacon used by the Trigonometrical Survey, stands about 300 feet above the level of the surrounding country. The general trend of the hill range is in a direction of S. 60° W. to N. 60° E., and there are several hills which branch from the main axis, usually more or less at right angles to it. The eastern half of the range over a distance of about half a mile only need be considered, as there are no rock exposures on the western half.

Early in January, 1916, Dr. O. P. Hay, of Washington, D.C., referred to me for description the fossil bone of a large bird that had been discovered in the eastern part of South Carolina some time previously. This specimen I at once recognized as the lower extremity of the right femur of some bird belonging to a species much larger than any existing form in the United States. I find this specimen to be thoroughly fossilized and of a dull-black colour, the edges of both condyles being considerably chipped off. On the antero-internal aspect the shaft appears to be cut away as if by some shaving implement. This, and where the shaft is broken nearly squarely across above, exposes a filling of a dense, very hard, pale-grey matrix, with a grain as fine as clay. Judging from this there should be no doubt but that this femur was a thoroughly pneumatic one in the living bird, and that the thickness of the osseous wall of the shaft was by no means great, as may be appreciated by examining the figures on the accompanying Plate XV.

On account of the aid it has given, palæontology has been termed the handmaiden of stratigraphy, but up to the present time petrology has not been called upon, so far as it might have been, to fulfil its appropriate duty towards the elucidation of the problems of stratigraphical geology and palæogeography.

A Careful examination of the distribution of the high-level gravels and sands of the Thames Valley, especially those associated with the boulder-clays, shows that in pre-Chalky Boulder-clay time, not only were the main valley lines marked out, but many even of the smaller valleys, such as the Brent, were in existence. Of course, during Pleistocene time, denudation has been very active; for over large portions of this area the boulder-clays, gravels, and sands now only occur as scattered patches.

In this group, shown in the sketch-plan Fig. 4, may be included the interesting pietre verdi areas (1) of the Rocciavré ridge on the right, (2) of Monte Rocciamelone on the left side of the Dora Riparia Valley, and (3) of the Rocciacorba ridge and the Avigliana belt of spurs where the Dora and the Sangone Rivers emerge from the Alps and enter the Po Valley about 20 kilometres west of Turin.

In a previous paper on the Permian Formation in the Alps of Piémont, Dauphiné, and Savoy, I referred incidentally to the large masses of pietre verdi or greenstones which constitute perhaps the most striking geological feature of the extensive areas covered by the crystalline rocks of the Piémontese Alps in a crescent-shaped curve about 200 miles in length from the Maritime range to Monte Viso, Grand Paradiso, and Monte Rosa. In the present paper I propose to deal more fully, although necessarily within narrow limits, with these pietre verdi which, owing alike to their extraordinary development, variety, and complexity, to their intimate association with each other and with the crystalline sedimentary rocks, and to their intricate composition and origin, have for the last fifty years presented most interesting problems and passed through many remarkable phases of interpretation. As a necessary preliminary to a description of the different areas, it will be convenient to briefly consider the most recent classification of the crystalline formations of the Piémontese Alps generally, and of the pietre verdi rocks in particular.

In the preceding paper I described the crystalline rock-areas of the Maritime and Cottian Alps: I now proceed to briefly review those of Northern Piémont forming part of the Grajan and Pennine Alps, under three heads—

I. The Lanzo Valleys and Gran Paradiso Groups.

II. The Dora Baltea (Val d'Aosta) Area.

III. The Lanzo, Ivrea, and Val Sesia Area.

They are shown in the sketch-map, Fig. 1. The conclusions in reference to the combined areas of the Piémontese Alps will be stated at the end of the present paper.

This district is of especial interest from the palæontological point of view in that the different members of the Upper Trias each afford a representative though not extensive flora and fauna. The scantiness of the material, in so far as the Lower Keuper and in some respects the Dane Hill Series are concerned, is due rather to the absence of good sections. This cannot, however, be said of the Rhætic beds, for the section at Glen Parva is one of the finest in the Midlands.

This, perhaps the most complex crystalline area of the Piémontese Alps, is also eminently sui generis, for it forms a unit of rocks outside, and different from the great calc-schist horizon with pietre verdi of secondary composition. As previously stated, it is the continuation of the mica-schist and minute gneiss belt which skirts the Po Valley from the Rocciacorba group to Avigliana, Monte Musiné, and Lanzo, and, extending from Lanzo to Ivrea, Biella, and Val Sesia, reaches beyond the latter into Lombardy to Lakes Orta and Maggiore. Within the Piémontese Alps, viz. from Lanzo to Val Sesia, it is bounded on the north by the calc-schist and pietre verdi fringe which skirts the Monte Rosa gneiss massif, and on the south by the Pliocene and Pleistocene deposits of the Po Valley, its superficial area being roughly 90 by 15 kilometres or 1,350 square kilometres, equal to over 500 square miles. The lower hills of the southern margin vary from 600 to 900 metres in altitude, which in the centre of the area increases to 1,000 and at the northern margin to 2,500 metres. In its general direction south-west to north-east, the area is intersected more or less at right angles by the following affluents of the Po: Stura di Lanzo, Malone, Orco, Chiusella – Dora Baltea, Elvo–Cervo, and Sessera–Sesia. The valley floors vary at the lower limit of the crystalline area from 300 to 500, and in their upper parts from 600 to 1,000 metres in altitude.

At about 55 miles we reach the Hendon Lobe fan. At Dollis Hill the base of the fluvio-glacial beds lies at a height of about 200 feet, whilst their upper limit at Hendon is about 280 feet. On Finchley Hill to the north-east the Boulder-clay lies between the levels of 240 and 340 feet. This was a small lobe, and the fluvio-glacial fan may have sloped rapidly towards the fluvio-glacial gravels of the main stream. On the section, Fig. 2, the heights are shown without correction for slope towards the River Thames.