During the last few years I have spent a considerable amount of time studying the geology of the country east of Llandrindod, but much still remains to be done, and the present paper merely embodies a few of the points which seem to be satisfactorily established with regard to a small portion of the area. Three distinct types of igneous rocks are recognized, and some facts and ideas with regard to each are put forward.

The Sierra Leone, from which the Colony of Sierra Leone takes its name, is a range of palm-covered hills running parallel to the coast (N.N.W.-S.S.E.). It is truncated on the north by the wide mouth of the Roquelle (Rokell) River, which forms the magnificent harbour of Freetown. Towards the south the range terminates at Yawry Bay. The length of the Sierra is therefore about 25 miles and its width, from Kassa Town to Kissy, about 8 miles. On the east side the range descends steeply to the Kwaia plain, from which it is separated by Waterloo Creek. The detachment of the hills from the interior lowland is sufficiently complete to entitle one to speak of the Sierra Leone Peninsula. Freetown is built on the north end of the peninsula, overlooking the harbour, and it straggles up from sea-level to a height of some 800 feet on Wilberforce Hill. The greater part of the peninsula is covered with thick tropical vegetation riglit down to sea-level; and an additional obstacle to geological study is created by the heavy covering of laterite which screens the rocks from observation. In places this laterite mantle is 30 feet thick. But along the northern shore of the peninsula, from Cape Sierra Leone to the mouth of Waterloo Creek, there are nearly continuous exposures of norite, and further useful exposures have been made during the construction of the Hill Railway and along certain of the roads on the hillside. These outcrops make it clear that the whole of the north end of the Sierra is formed of norite, and it would not be surprising to learn that the entire Sierra has the same composition.

Since Salter, in 1865, published his classification of the species of the genus Homalonotus, no detailed attempt has been made to re-arrange the increased number of species now known into natural groups. Salter was not convinced that his scheme was satisfactory, and appears to have regarded it as largely artificial, though convenient. The divisions instituted or recognized by him bore the names Brongniartia, Salter, 1865 (divided into two sections); Trimerus, Green, 1832; Kænigia, Salter, 1865; Dipleura, Green, 1832; and Burmeisteria, Salter, 1865.

In South-Central Western Australia, in the physiographic division which the writer has termed the Central or Salt Lake Division, in a large portion of which the average annual rainfall is about 10 inches per annum, numerous “dry” lakes or playas occur. These have been described and the question of their origin has been discussed by various authors. They have been differently regarded as due to glacial, marine, and wind action; also as the remains of old Tertiary rivers now largely obliterated by drifting sands; and also (in part) as deformation basins. Most writers agree that they have been formed under subaerial conditions, and probably most will ultimately agree that deformation is responsible for some at least of the lakes, or has aided in their formation.

Some years ago I published, with the late Professor T. Rupert Jones, F.R.S., a description of two small Limuloids referred to the genus Bellinurus, sent me by ray friend Dr. H. M. Ami (then of the Canadian Geological Survey), who obtained them from the Lower Carboniferous Marine Series on the Intercolonial Railway of Canada, in Colchester County, Nova Scotia (Geol. Mag., 1899,pp. 387–95, PI. XV, Figs. 2 and 3), under the specific name of B. B. grandævus. Fig. 2 was collected from the sixth cutting east of Riversdale Station and Fig. 3 from the third cutting east of Colnary River.

Some years ago I was allowed to publish in the Geological Magazine some papers on the recent geological history of the Baltic, in which I tried to bring before English readers the very important discoveries of the Northern geologists as affecting the general geology of the north-west of Europe and to extend their deductions. I was obliged to interrupt them for other work. Perhaps you will allow me to continue them some steps further, as we had reached a stage of some interest.

In an interesting paper lately published my friend Mr. R. B. Newton has expressed the opinion that the Coralline Crag should be grouped with the Diestien and Anversien of Belgium as Upper Miocene, the fauna of the Suffolk boxstones being regarded by him as Middle Miocene. The recent researches of Mr. Alfred Bell have led me to agree with Mr. Newton that the latter is pre-Pliocene, but I regret I cannot accept his view as to the age of the Coralline Crag, which I consider to be more nearly related to the Waltonian horizon of the Red Crag than to the Belgian Miocene.

The new genus, Liothyrella, has recently been created by Dr. J. Allan Thomson for the reception of a series of recent and fossil Terebratulids commonly ascribed to the genus Liothyrina. The chief characters upon which the genus is founded are the presence of fine radial ribbing on the surface of the shells and the possession of a short, low, thin, mesial septum in the dorsal valve. In the thickness of the shell, Liothyrella is said to stand between Liothyrina (genotype L. vitrea) and Terebratula, sensu str., all three genera being finely punctate. Thomson takes the; recent Magellanic species L. uva (Brod.) as the genotype of Liothyrella, and includes in the same genus L. uva, var. notorcadensis, Jackson, from Scotia Bay, South Orkneys, and a new species dredged off Tasmania by the Mawson Expedition, as well as two Australian Tertiary species, Terebratula tateana, Tenison-Woods, and T. concentrica (Hutton). He remarks that “probably also many of the other southern species ascribed to Liothyrina will be included here, but the descriptions do not state whether or not a mesial septum is present” (op. cit., p. 44).

There is a regrettable tendency to looseness of thought among geologists on the subject of isostasy. I give no quotations in support of this assertion, firstly because, being always in the form of casual allusions to the principle, they would require long hunting down; and secondly because, if given, they would fasten upon a few individual geologists a criticism which should be more general. The usual form in which the looseness of thought shows itself is in explanations of shallow-water deposits of thickness greater than their depth of accumulation. We are frequently told that such thick deposits result from local subsidence due to the loading of the sea-floor by the great weight of sediment, and reference is made to the principle of isostasy as justifying this explanation.

Kaolin occurs abundantly in the Federated Malay States in connexion with granite, and is certainly formed on a large scale by weathering. The purest kaolin in large quantity, however, is found as veins in clay above limestone at Gopeng and elsewhere in Kinta, and in quartzite and shales near Tanjong Malim and Kerling. The purity of these veins and the information obtained about those in Kinta when traced down to limestone, lead to interesting considerations about their origin, and the nature of the material in the limestone is a matter of importance in connexion with the possibility of establishing a kaolin industry.

Before returning to Calcutta the specimens described in his memoir “Ordovician and Silurian Fossils from Yun-nan” (1917, Palseont. Ind., N.S., vol. VI, Mem. 3), Dr. F. R. Cowper Reed very kindly lent to the Geological Department of the British Museum the figured cystids, in order that plaster casts of them might be made and kept there for reference. This was done, and a set of the casts was also furnished by the Department to the Sedgwick Museum, Cambridge. While preparing the specimens for the moulder, I had the opportunity of studying them with some care. Although Dr. Reed has published good figures, drawn with Mr. T. A. Brock's usual exactitude, and descriptions, on the fulness of which he will perhaps allow me to compliment him, nevertheless the notes made by me, when still unacquainted-with his valuable work or with the views therein expressed, do contain supplementary matter, which it seems better to publish now rather than to reserve for some revision in an uncertain future.

In an article by Dr. H. Jeffreys in the Geological Magazine for April, pp. 215–19, an attempt is made to show that the discovery of radio-active materials in the earth's crust favours the “contraction and puckering” theory of mountain building. With regard to 0. Fisher's view he writes, “It rests entirely on Kelvin's theory of the cooling of the earth, which has had to be completely revised on account of the discovery of the extensive distribution of radio-active matter in the earth's crust. The time available has been found to be about twenty times greater than on Kelvin's theory, and the cooling has therefore had time to extend to a much greater depth and to produce a very much greater compression.” We are also told what the reduction in the earth's diameter has probably been, and the actual depth of Fisher's level of no strain.

The type of this section is the Lower Devonian species Homalonotus Herscheli (Murchison) from South Africa and the Falkland Isles. The characters of the section were stated by Salter to be as follows: “Elongate, convex; head triangular, eyes approximate on gibbous cheeks. Glabella distinct, lobeless, spinous. Thorax slightly lobed and spinous, as is also the many-ribbed pointed tail.” It should at once be stated that the type-species has neither a lobeless nor a spinous glabella, and Salter apparently added in these characters from the Rhenish H. armatus, Burm., which he included in the section. The only British form quoted by Salter is one from Devonshire based on a pygidium which does not conform to the above definition and was described under the name H. elongatus. Woodward, in reviewing the Devonian species of Homalonotus, follows Salter in including the latter species in Burmeisteria.

A recent attempt by the writer to utilize the information at present available with a view to gaining some notion of the dominant characteristics of the denudation suffered by the Chalk of the London Basin prior to the deposition of the Eocenes yielded results of sufficient interest to encourage him to apply the same method of analysis to the East Anglian area.

At the present time a large proportion of the world's supply of tungsten ores comes from secondary (detrital) deposits of various kinds, formed by the normal denudation and redeposition of primary ores exposed at the surface to the agents of weathering and transport. It is impossible to form any idea of what fraction of the world's output actually comes from these sources, since the published statistics do not draw any distinctions in this respect', but the amount is undoubtedly large. Although of such great economic value, the secondary deposits do not show any features of special interest, and a lengthy description is unnecessary.