The Buchholm Sandstones.—These beds are characterized by the evidence they afford of having accumulated in shallow water. They consist generally of gritty greywackes and light green or red, sandy, incoherent shales and mudstones.

A Recent short stay on Antigua has enabled me to inquire into a few points in the geology of that island. Among the matters of interest were to investigate the crucial question of the age of the Seaforth Limestone, which carries with it the age of the volcanic mountainous part of the island. Also to inquire into the supposed occurrence of Cretaceous Chalk at Cassada Gardens; to see some of the igneous intrusions in the Central plain and the Antigua Limestone; to collect the freshwater mollusca of the silicified tuff beds; and to search the Antigua Limestone for the so-called “Oligocene rudist”, Neomonopleura (Rothpletzia), which Dr. Lehner told me he thought occurred at Hodge's Bay. The sub-fossil land shells in the Pleistocene marls at St. George's Church also interested me, among other matters.

The claims of the sea as a denuding agent have been much disputed of late years; the meteoric and fluviatile theories of denudation have been revived; and the glacial theory has been extended, so as to encroach on what was once generally admitted to be the legitimate province of the sea. But, as a forgetfulness of, as well as too much reliance on, the power of the sea to modify, may become a fertile source of hasty and false generalization, it is well that the importance of waves, tides, and currents, as denuding causes, should be re-asserted, and attention directed afresh to the more striking monuments they have left behind them in regions removed from their present theatre of action. These monuments present an unmistakeable resemblance to the cliffs, buttresses, walled inlets, pillars, needles, &c., now in course of being formed by the sea; and in explaining them, the old principle of sound theorization —similar effects are referable to similar causes —is not to be set aside by overstraining the capabilities of any theory which will merely account for the phenomena.

As shown by his paper on “The Age of the Rocks and Topography of Middle Northern Iceland” (Geol. Mag., LXXV, 1938, 289–296), Dr. Hawkes realizes the great change of view concerning fundamental features of Icelandic geology necessitated by my discoveries in North Iceland of Pleistocene metamorphic glacial deposits. In fact, the changes involved seem to him so great that he finds the whole thing incredible, and he rejects what he terms my hypothesis. In this incredulity, I think, is to be found the reason for his being unable to repeat for himself some observations I made on the eastern side of Fnjóskadal. That I should have been mistaken is, I think, out of the question; a typical “striated pavement” is something a geologist of some experience cannot be mistaken about. In Skridugil I exposed a surface which quite definitely exhibited traces of glacial action. That “similar deposits” to those overlying the pavement “are found at various horizons in the older Tertiary Series of Iceland” (Hawkes, op. cit., p. 293) is unknown to me. The name “Skridugil” was given to me by a man who may not have understood to which locality I was referring.

Recumbent shear folds and their related structures in the Mylor Slates are briefly described. It is concluded that folding has been produced by subhorizontal shearing stresses acting in a northwesterly or south-easterly direction.

High-precision U-Pb zircon ages on SE Newfoundland tuffs now bracket the Avalonian Lower–Middle Cambrian boundary. Upper Lower Cambrian Brigus Formation tuffs yield depositional ages of 507.91 ± 0.07 Ma (Callavia broeggeri Zone) and 507.67 ± 0.08 Ma and 507.21 ± 0.13 Ma (Morocconus-Condylopyge eli Assemblage interval). Lower Middle Cambrian Chamberlain’s Brook Formation tuffs have depositional ages of 506.34 ± 0.21 Ma (Kiskinella cristata Zone) and 506.25 ± 0.07 Ma (Eccaparadoxides bennetti Zone). The composite unconformity separating the Brigus and Chamberlain’s Brook formations is constrained between these ages. An Avalonian Lower–Middle Cambrian boundary between 507.2 ± 0.1 and 506.3 ± 0.2 Ma is consistent with maximum depositional age constraints from southwest Laurentia, which indicate an age for the base of the Miaolingian Series, as locally interpreted, of ≤ 506.6 ± 0.3 Ma. The Miaolingian Series’ base is interpreted as correlative within ≤ 0.3 ± 0.3 Ma between Cambrian palaeocontinents, although its exact synchrony is questionable due to taxonomic problems with a possible Oryctocephalus indicus-plexus, invariable dysoxic lithofacies control of O. indicus and diachronous occurrence of O. indicus in temporally distinct δ 13C chemozones in South China and SW Laurentia. The lowest occurrence of O. indicus assemblages is linked to onlap (epeirogenic or eustatic) of dysoxic facies. A united Avalonia is shown by late Early Cambrian volcanics in SW New Brunswick; Cape Breton Island; SE Newfoundland; and the Wrekin area, England. The new U-Pb ages revise Avalonian geological evolution as they show rapid epeirogenic changes through depositional sequences 4a–6.

The Viggiano Mt. platform carbonates form a layered succession cross-cut by a dense array of pressure solution seams, and five sets of fractures and veins, which together form a sub-seismic structural network associated with polyphasic tectonic evolution. To assess the influence exerted by depositional and diagenetic heterogeneities on fracture geometry, distribution and multiscale properties, we present the results of stratigraphic, petrographic, mineralogical and mesoscale structural analyses conducted at the Viggiano Mountain, southern Italy. Based on rock textures and fossil associations, we documented that the Sinemurian–Pleinsbachian carbonates were deposited in a low-energy open lagoon, the Toarcian carbonates in a ramp setting rimmed by sand shoals, and the Cenomanian carbonates in a medium- to high-energy, lagoonal–tidal setting. Fracture-density (P20) and intensity (P21) values computed after circular scanline measurements show similar trends in both Sinemurian–Pleinsbachian and Toarcian carbonates, consistent with the bed and bed-package heterogeneities acting as efficient mechanical interfaces during incipient faulting. On the other hand, P20 and P21 do not show very similar variations throughout the Cenomanian carbonates due to pronounced bed amalgamation. Throughout the study area, the aforementioned parameters do not vary in proportion to the bed thickness, and show higher values within the coarse-grained carbonate beds. This conclusion is confirmed by results of linear scanline measurements, which focus on the P10 properties of the most common diffuse fracture set. The original results reported in this work are consistent with burial-related, physical–chemical compaction and cementation processes affecting the fracture stratigraphy of the Mesozoic platform carbonates.

The area to the north of Barnstaple (North Devon) was covered by a detailed gravity survey. The main gravity gradient of the Bouguer anomaly map (estimated to be 1·2 mgals per mile) confirmed the conclusions drawn by Bott et al. (1958), who attributed it to a basin of possibly Carboniferous sediments and/or Old Red Sandstone, about 4 miles thick, separated from the outcropping Devonian rocks by an assumed thrust plane.

A negative residual gravity anomaly is located over the outcrop of the Pickwell Down Sandstone. Analyses of the anomaly show that it is caused by the southwards dipping belt of sandstone and that the angle of dip of the formation decreases with depth. At a depth of about 2 miles the formation becomes nearly horizontal. Alternatively, it may terminate against an assumed thrust plane underlying the whole outcropping Devonian.

The aeromagnetic map of the area shows an elongated magnetic “high” following the outcrop of the Morte Slates. The anomaly is probably caused by near surface, highly magnetized rocks in association with the Morte Slates.

Whilst studying the sedimentary roofing-slates of North Wales and Cornwall, and allied materials, my attention was also directed to those most interesting rocks, the ash-slates of the Lake District, often externally so closely resembling some of the Welsh and Cornish examples, though differing so much in origin. In course of time I have collected, and had sections prepared from, a considerable number of specimens from many quarries and other places at various parts of the district, both very fine-grained wellcleaved actual roofing-slates and also the attendant coarser beds.

Since the publication of the paper by the present author in 1905 on the Classification of the Phacopidae, a considerable advance has been made in our knowledge of this family as a result of further and better material being obtained, and of new discoveries in different parts of the world. Many new genera and subgenera have been instituted, and modifications or limitations of some of the old terms have been introduced by various authors. The work of Wedekind, Clarke, Rud. and E. Richter, and Kozlowski has specially dealt with questions of classification, but there is still a considerable amount of diversity in the usage and application of the generic and subgeneric names.

The Upper Llandeilo Rocks of the South of Scotland have long been known to yield graptolites in great profusion, few other forms of animal life being recognised as occuring in them. Having, this summer, had an opportunity of examining the graptolite-shales of Garple Linn, near Moffat, I was struck with the occurrence in them of numerous bodies, differing from the graptolites in form, though resembling them in mineral texture.

In the almost complete absence of fossils in the British Keuper there has been a lack of datum-lines in that formation by which we may compare the horizons of different sections. Yet in such a thick and widely spread deposit it is very desirable to have subdivisions enabling us to give the particular part of the Keuper to which a section belongs. In deposits such as the New Red formations too great stress has been laid on lithology, inevitable perhaps in the scarcity of fossils, but a source of grave errors in correlation. For example, Mr. L. J. Wills thinks that fossils found in the Keuper of Warwick have affinity, not with the Keuper, but with the Muschelkalk of Germany. Again, there are strata in the Permo-Bunter of Nottinghamshire which might be mistaken for Keuper Waterstones, if only lithology was considered. Over small areas a band of sandstone with some peculiarities may be used as a datum-line, as in the Arden district of Warwickshire and in Nottinghamshire, but these are of local value only.

A Small series of rock-specimens, consisting chiefly of fragments of basalt, dolerite, volcanic conglomerate and tuff, which were collected near Kilima-njaro, by F. Holmwood, Esq., C.B., lateConsul-General at Zanzibar, was recently forwarded to the Museum at Jermyn Street, and placed by Dr. A. Geikie in my hands for determination. Among these specimens was a small block, the crystalline texture and high density of which at once arrested attention Freshly fractured surfaces of this rock present numerous glistening facets, which with the aid of the pocket-lens are seen to be the cleavagefaces of a yellowish-green, a dark-green, and a garnet-red mineral. These minerals are respectively olivine, hornblende, and hypersthene in nearly equal proportions, the hornblende being perhaps slightly predominant. They form a holocrystalline granular aggregate, in which the.grains are of nearly equal size and without crystalline contours; in other words, the structure is allotriomorphic-granular. Subordinate both in size and quantity to the three principal constituents is magnetic iron-ore.

(1) Reasons are given for believing that the holotype of Anthracomya adamsi Salter (the genotype of Anthracomya) has been correctly identified.

(2) It is shown that the horizon of this presumed holotype is near the middle of the Similis-Pulchra Zone, and is near if not identical with the horizon of A. hindi Wright.

(3) Anthracomya adamsi at that horizon has no close connection with A. modiolaris (from which it may, however, have been derived at a lower horizon). The distinction of these two forms is discussed, and it is suggested that among well preserved specimens only very occasional variants cause any difficulty in identification. The shells referred to A. adamsi. s. lat. by Weir and Leitch from the base of the Similis-Pulchra Zone (1936) are not considered in this paper.

(4) The relations of A. adamsi, A. hindi and A. warei are briefly discussed: in view of the limited distribution of the various species it is thought best for the present to retain the three specific names.

My attention has been drawn to a recent notice' by Mr. Colesof a quartzite at Martley. Since this area is included withinthe district of the Malvern and Abberley Hills, which I have beenengaged in studying for more than two years, a brief descriptionof the relations of the rocks, as determined by myself in Januaryof the present year, may not be out of place. The small patch of interesting rocks here is likely to become covered up as cultivation progresses; indeed, the exposure is evidently much less extensive than it was when Phillips described it in his memoir on the Malvern and Abberley Hills. Mr. Coles has, moreover, I think, hardly done justice to the remarkable section exposed here.

In this paper I propose to deal with the question set forth in the title in connexion with the recent works of different authors. Owing to the difficulties of international communication, I was unable until quite recently (1922) to consult the general works on the Rugosa corals published by Faurot, Jaekel, and Robinson.