Since the publication of an earlier paper by Mr. Charles Elton and myself (1931), further Quaternary fossils from Spitsbergen have been identified by me, including a lamellibranch (Macoma) which, I believe, has not been recorded previously from Spitsbergen, but which is similar to a form described by Brøgger from the Yoldia Clay of the Oslo district.

Anyone who studies the relation of the rocks of the Lizard Peninsula to those immediately to the north must realize that Porthallow, the little village in a sheltered cove near St. Keverne, is a critical locality in the problem, and one indeed that may hold the key to the solution of the relative ages of the rocks on either side of the sinuous line called the Lizard Boundary. Porthallow is at the eastern extremity of that line. The western extremity is on Polurrian Beach, near Mullion, where a very clear fault with a breccia about 22 feet thick separates two totally distinct formations, sandy and argillaceous killas on the north from hornblendegneiss on the south. At Porthallow, however, although there are cliffs on either side of the cove washed by the sea, the geology is far from having the textbook clearness of Polurrian Beach and there is room for much difference of opinion. Text-fig. 1 is a sketch-map of the locality based on the Ordnance Survey 25 in. to the mile map, and first the main features of the geology will be described. For the neighbouring country the reader is referred to the Survey 1 in. map (Sheet 359) and to the 6 in., Sheet lxxxi N.E.

For many years I have been interested in the colloidal nature of coal. As long ago as 1914, in discussing the coal resources of Korea State in the Central Provinces of India, I suggested that the bright bands of the Korea coals are colloidal. It is suitable to quote here the exact words used:—

Reptilian bones, first observed by Mr. C. I. Gardiner in 1935, are found in two quarries in the Chipping Norton Limestone (top of Inferior Oolite, fusca and zigzag hemerae). These two quarries are the New Park Quarry, about 2½ miles N.W. of Stow-on-the-Wold, and the Oakham Quarry which lies about a mile W.N.W. of Little Compton. The bones occur in a hard cream-coloured limestone which is worked for road-metal. Fossils other than reptilian remains are not common, but among those found in the New Park Quarry is an ammonite determined by Mr. J. W. Tutcher as Parkinsonia neuffensis Oppel. The great majority of the bones come from the New Park Quarry, but the Oakham Quarry yielded certain of the crocodilian, theropod, and sauropod bones.

Previous opinion sums up in favour of the continuity of the three boundaries, the entire line being one of dislocation in the east, dislocation and intrusion in the west. Previous opinion also favours the view that, inside the boundary-zone, not only are the Start-Lizard schists continuous, but they have features comparable with some of the Alpine “Schistes lustrés”, with recumbent folding at the Lizard.

The boundary-zone is defined as a belt of variolite (ophiolite), exotic blocks, and serpentine intrusive in, and contemporaneous with, a great thrust.

Recent work by the writer has shown that some of the beds outside the boundary-zone are a “facies flysch”. Younger beds come in towards the west, in association with the westerly pitch visible in the older beds in South Devonshire; geanticlines occur in the Lower and Middle Devonian respectively, of South Devon and South Cornwall. In an area further north some of the beds show an accumulation of folds comparable with those of the “autochthonous sedimentary” in front of some of the great Alpine nappes; recumbent folding is prevalent in both Devon and Cornwall. The Cornish Flysch was deposited under conditions such as might have preceded a great nappe movement; it is described in relation to the exotic blocks and serpentine in the fracture.

The much younger Alpine Flysch also includes ophiolites and exotic blocks, with serpentine intrusive in the fractures upon which the great nappes advanced. According to some authors, the nappes arose from recumbent folds based on geanticlines.

The similar direction of both the Cornish (Variscan) and the Alpine movements makes possible a comparison in certain effects as, for instance, the southward increase in albitization and metamorphism, between the great Alps and the similar but older, comparatively tiny, flattened, and denuded relic in south-west England.

These cases are also strikingly paralleled by a zone of basic igneous rocks and exotic blocks which overlies the Himalayas.

The evidence appears sufficient basis for the suggestion that the Start-Dodman-Lizard boundary-zone may be the relic of a great Variscan nappe, associated with the fan-structure of Cornwall.

A review of the literature, and our own observations have led us to the conclusion that granitization, widely defined as the process by which solid rocks are converted to rocks of granitic character, has been an important process in the evolution of many subjacent masses of granite and allied rocks, such as granodiorite and diorite, in erogenic regions.

Granitization of pre-existing rocks seems to involve two processes: (a) Metasomatism under the influence of permeating highly energized fluids—emanations—ahead of advancing magma; and (b) Mechanical penetration by magma. During the first process metasomatic exchanges take place between the minerals of the country-rock and its pore fluid: the reactions tend towards the achievement of equilibrium under the existing physico-chemical conditions. This metasomatism is selective, and promotes the convergence, in bulk and mineral composition, of rocks which were originally different, towards a common end-product. During the early stages conditions are essentially those of thermal metamorphism, but with rising energy level and increasing magmatic contributions the final conditions are dominantly “igneous”.

The mechanical penetration of the altered rocks and their mixing with magma may follow the first process without a break. Alternatively, intrusion may occur before metasomatism is completed, or has even had appreciable effect. The mixing or intrusion stage is accompanied by reactions, which tend towards the attainment of equilibrium, under magmatic conditions, between the magma and the foreign material. In terms of bulk composition the products will be intermediate between that of the magma and that of the incorporated material.

The metasomatism trends of the various examples that we have discussed are plotted together in Text-fig. 8. The diagram brings out the convergence of the curves from the normal sedimentary field to the rhyolite-diorite line, which is itself the locus of mixtures between metasomatized products and acid parental magmas.

Granitic rocks may originate as the result of either or both these processes. That which predominates in any particular case depends on the supply of emanations and the local physico-chemical conditions. In the deeper parts of the granitic layer complete or selective fusion is to be expected, and the magmas so formed may rise and granitize the overlying rocks: firstly, by metasomatism, and at higher levels chiefly by mechanical penetration. At still higher levels, owing to loss of energy, rising magma is unable to cause extensive modification of the pre-existing rocks, and forms true intrusions.

The purpose of this note is to call attention to the occurrence of a Chalk sea-urchin, apparently hitherto unrecorded from England, in the hope that field-workers may be able by collecting to determine its zonal range and importance, if any, as a zonal guide. Since it resembles superficially both the common Offaster pilula (Lamarck), and also very small specimens of Echinocorys scutatus Leske, it has possibly escaped recognition.

It is still fresh in our memory that the Geological Society of London made a bold attempt a few years ago to arranga a wide-ranging discussion on the problem of continental drift. On an occasion of this nature one might be tempted to imagine a scene as lively as that when the Wernerians and Huttonians met at the Castle Hill of Edinburgh. But the opponents of the hypothesis, as the report revealed, seem to have stood no less firm than do the continents, as they hold. One looks in vain, since the publication of the American Symposium, for a change in the trend of opinion. This, however, does not mean that the problem is closed. We thus welcome the fresh lead given by Dr. A. L. du Toit in his recent volume on Our Wandering Continents.

Certain conclusions on distribution and migration have been reached by Dr. W. K. Spencer2 from his detailed studies of Palaeozoic Asterozoa and in conversation he has frequently expressed the wish that he might be able to compare these with data derived from similarly focused studies of other animal groups. It is reasonable to assume that the final story of migration of faunas in the Lower Palaeozoic British area cannot be told until the inequalities of fossil-collecting and naming have been overcome and until more is known of the stratigraphical position of certain faunas; any conclusions made at the present stage are tentative and are offered as an incentive to research.

In 1901 (Swansea Memoir, p. 5; West Gower Memoir, p. 4) the Officers of the Geological Survey (R. H. Tiddeman and B. S. N. Wilkinson) discovered olive-coloured shales and mudstones in outcrops on Cefn Bryn, Gower. They considered these strata to be “succeeded naturally by Old Bed Sandstone”, for the larger outcrop is bounded on the south by brown sandstones and quartz conglomerates dipping southwards at about 30 degrees. It was therefore natural that these beds, apparently obviously older than the contiguous Old Red Sandstone, should be referred to the Silurian. Tiddeman obtained fossils from the shales which were identified by E. T. Newton as “Rhynchonella (like R. nucula), Bellerophon (like B. murchisoni), Modiolopsis?, Chonetes sp., crinoid ossicles, and entomostraca”. The evidence of the fossils thus seemed to confirm the conclusions made on the field evidence, though (as shown by the private records of the Geological Survey) Newton was doubtful of the precise age of the fossils and questioned their reference to the Ludlow.

The mica mines of the Kodarma area in the Hazaribagh district of Bihar contribute as a single unit the largest quantity of muscovite (locally known as “Ruby mica”) to the world. The mica-pegmatites of this area have attracted the attention of geologists and mining engineers since the beginning of the last century, but still many petrological problems connected with them have not been satisfactorily solved. During recent years the present authors have studied the geology of the Government Reserve Forest of Kodarma; and they intend to discuss in this paper the origin and the characteristic features of the Kodarma pegmatites and to review the literature already existing on this subject.

During last winter (1937) at Cottesloe, a seaside suburb of Perth, Western Australia, a large sand-dune was being levelled. This provided the writer with an excellent opportunity for observing the movement of sand grains by wind.

This well-known genus presents a nomenclatorial problem apparently even simpler than that of Mortoniceras, dealt with in the first article of the present series, yet I can foresee considerable opposition to the views here put forward. It is, of course, agreed that “names now current are not to be discarded unless the reasons for change show a clear-cut necessity” (Opinion 93); but since “priority of actual date” is quoted as an example of such necessity, I consider that we shall have to change our present interpretation of Pachydiscus, however irksome the change may be to some.1

During my visit to Malaya in 1938, for the purpose of reporting to the High Commissioner upon the mineral industry of that country, I noticed in cuttings at two places exposures of banded rocks of alternating light and dark tints that recalled the varved sediments of other parts of the world. As such rocks have not hitherto been described from Malaya, and as varved sediments are everywhere considered to be of much interest, a brief note upon these Malayan occurrences seems desirable, in case they should prove to be of similar origin.

The fertile highlands of Kenya, of which the great mountain of that name is the northern outpost, are divided from those of Abyssinia by a great desert nearly 400 miles wide. This tract is a gneiss peneplain of great age, whose degradation, without any regional interruption, has continued since Palaeozoic times. At the present date its undulations are scarcely noticeable, and its ill-supplied rivers do not often reach the coast. Such is the Uaso Nyero, which, rising from the north-western slopes of Mount Kenya, and running spasmodically for 200 miles eastwards through this desert, finally dies away in the great swamp called Lorian, which shifts its position up or down the valley in accordance with the seasons. The Tana River reaches the sea, and its valley also has the appearance of great antiquity; the long slopes down to the valley from its sides are hardly perceptible, and for two-thirds of its 400 mile course the river meanders sluggishly from one side of its valley to the other.

During a recent survey of the Lower Old Red Sandstone lavas of North Fife a small unrecorded mass of diorite was found by Dr. F. B. A. Welch. The rock of this intrusion is so much fresher than that of other diorites in the Ochil range that it seems worth while to give an account of its mineralogy and petrology.

Recently, in describing the fauna of the passage-beds between the Dinantian and the Namurian, I pointed out, for the first time, the presence of some Conodonts1 in the Carboniferous of Belgium. Since the discovery of this first series of specimens, I have picked up several hundred Conodonts in various localities, included either in the passage-beds, or in the lower levels of the Namurian. It is to be expected that other localities may shortly be discovered.

It is proposed in the present paper to discuss certain micrometric methods applicable to the minerals of sedimentary rocks and to suggest how their graphical study may be used for the elucidation of certain problems in sedimentary petrology. The examples used are taken chiefly from the Triassic and Jurassic rocks of Yorkshire as described in Part I.1

The muscle systems of Lingula, Discinisca, and Crania have been described in considerable detail and in general with progressive accuracy by numerous workers since the time of Cuvier and Owen, and the best and apparently most recent accounts are to be found in two works by Blochmann (1892, 1900). But I am not aware that there exist any diagrams of these systems readily accessible to the palaeontologist; Fischer and Oehlert (1887) give some figures adapted from Joubin (1886), but these are in some respects inaccurate and Blochmann's work, other than on Crania, has not apparently found its way into palaeontological literature. The purpose of the present note is little more than to provide diagrams of the shell muscles of the above-mentioned living genera, and to attempt certain palaeontological restorations. I have had the opportunity of verifying the structures in spirit Lingula and to some extent in Crania, thanks to the kindness of Dr. C. F. A. Pantin.