In the Harlech Grit Series pyrite always occurs associated with rocks of practically all grades. It is, on the whole, of least importance in the grits, but even in these it becomes locally fairly abundant. Among the mudstones it occurs concentrated into layers, which are relatively persistent laterally. Immediately below the manganese-ore of the Manganese Shale Group, for example, there occurs a very widespread band of green mudstone which contains abundant pyrite crystals. Although its general characters are the same this band varies slightly, in detail when traced laterally and it is with these variations that the present paper is largely concerned. This band is usually 1 to 2 inches thick and is usually of dark green mudstone, though rarely it is of the normal blue-grey colour. The pyrite crystals vary from very minute to about ⅜ inch in size. In addition, pyrite occurrences from other rocks are described. The account is particularly concerned, not with the pyrite crystals themselves, but with zones of authigenous minerals which almost invariably surround them in these rocks.

In the Scottish Lower Carboniferous limestones there are known to occur at least sevenspecies of Dicyclic Inadunate crinoids belonging to the family Poteriocrinidae, one of the main characters of which is the possession of five simple unbranched arms. One species is also known from the Carboniferous of the Isle of Man. Two of the Scottish species have been assigned to the genus Ulocrinus, viz. U. globularis de Koninck and U. doliolus Wright. The former species is now referred to U. bockschii (Geinitz), which has priority, and the Scottish specimens as they commonly occur appear to be indistinguishable from it. The cup in these two species is specially characteristic, the shape being for the most part globular and the anal area, while sometimes of normal character, is more commonly occupied by a large RA with anal X and rt surmounting it and comparatively small. The arms are rather long, uniserial, and formed of narrow cuneiform brachials (Plate XIV, Figs. 1–6). (Bather, 1916–17; Wright, 1927, 1936.)

In the course of work in collaboration with Dr. J. E. Hemingway on the petrography of the Dogger of North-East Yorkshire it has been found that brookite is widely distributed as a “heavy mineral” constituent in several different kinds of sediment. This is in agreement with results obtained earlier by myself alone in the study of sandstones from higher horizons of the Middle Jurassic in Yorkshire. Although it does not yet appear that the distribution of brookite in the Dogger is of any particular significance, nevertheless the mineral itself shows interesting peculiarities and variations; a detailed discussion of these would be out of all proportion in the paper which we hope to publish shortly on the character and distribution of the Dogger in general; and it has therefore been decided to give here a brief and mainly mineralogical account of the different varieties of brookite met with, without discussing the general problem of the abundance of titanium minerals in the Yorkshire Jurassics and their local distribution.

During recent work on a collection of Camerinidae from Mexico the species recently described by M. G. Rutten, from Cuba, were considered in some detail, since Cuban and Mexican foraminiferal faunas show close affinities. No Cuban species of Camerina or Operculina were found in the Mexican Tertiary material, but some interesting points were discovered regarding Camerina petri Rutten.

To compare a rising island (Barbados) with one supposed to be sinking (Malta) two visits were paid to Malta and Gozo in 1933 and 1936 of four and six weeks’ duration. One is soon convinced that a good deal is yet to be learnt about these islands, especially as regards the later deposits. The Pleistocene beds of the Maltese islands occur as a number of separated deposits and can be classified into:—

In 1904 the late Dr. Arthur Vaughan, in collaboration with the writer, described1 the Rhaetic rocks exposed in constructing the South Wales direct branch of the Great Western Railway between Stoke Gifford and Chipping Sodbury. During the last few years, extension of the big quarry in Carboniferous Limestone at Chipping Sodbury has exposed a fine section of Rhaetic, the description of which and of the field relations of the associated rocks is the object of the present paper.

Before proceeding further with these notes on the geology of The Lizard it will make matters clearer if the sequence of rocks is given as established by the Cornish and other geologists, but I have ventured to introduce modifications which will be explained later:—

Youngest: Kennack granite.

Kennack gneisses, consisting of doleritic and granitic components.

New analyses are given of the Glen More Ring-dyke. The basic end of the variation diagram is found to differ considerably from that of the Normal Magma Series. The magma variation is explained by gravitative sinking of augite and iron-ore (and plagioclase), the olivine of the Normal Series playing only a subordinate part. Various objections are brought forward to the explanation of the magmas by hybridization. The peculiar microscopic aspect of the intermediate rocks is tentatively attributed to pneumatolytic emanations from the lower reaches of the column. It is shown that a gradual transition from basic to acid already existed before the final consolidation of the magma took place.

The investigation of submarine canyons has been actively pursued in the United States of latter years, principally due to the activities of F. P. Shepard. The Coast and Geodetic Survey has mapped a large number of these interesting chasms, both along the Atlantic and Pacific continental slopes, by sonic soundings; Shepard himself added data by soundings and dredgings along the Californian coast; Stetson performed current measurements, dredgings, and sampling in the canyons off the east coast. The number of data is steadily increasing in the United States, and it is to be hoped other nations will also become active, for much still remains to be learned before a comprehensive view of the many-sided problem can be obtained.

The composite granodiorite batholith of the Kopaonik Mountains forms one of the more southerly members of the peri-Adriatic tonalitic intrusions. In the area discussed in this paper it intrudes a series of sedimentary rocks which range from dominantly calcareous to pelitic types. Metamorphism of these rocks has produced crystalline limestones, skarns, and calc-silicate hornfelses, which grade downwards into mica-, amphibole-, epidote-, and locally cordierite-bearing rocks. The pelitic and amphibole-bearing hornfelses are in immediate proximity to the batholith on the surface. The amphibole-bearing types are mainly confined to a relatively small area, well within the zone of high-grade metamorphism and overlying the southerly pitching nose of the intrusion. With them are associated hornfelses which carry porphyroblasts of albitic feldspar. It appears that the persistence of the amphibole and the development of these feldspar porphyroblasts may have been caused by hydrous and probably sodic emanations which permeated the sediments above and ahead of the advancing igneous mass.

Northern Iceland between Skagafjord on the west and Skjalfandi Bay on the east is a deeply dissected upland built up of plateau basalts with subordinate intercalations of clastic volcanic sediments. The main valley, the Eyjafjord, is traceable northwards as a groove in the sea floor down to–500 metres. To the east of the upland the country is less elevated; marine Pliocene deposits are present in the Tjörnes peninsula, and recent lava flows are prominent. The contrasted regions adjoin along the BarQardal fault running N.–S. and marking the western boundary of the great graben which has been the site of Recent and Quaternary volcanic activity. Thoroddsen considered the upland rocks to be Tertiary (Miocene) in age, and that the Pliocene sediments had been laid down in a bay formed after the faulting and erosion of the older series.

The transformation of sedimentary rocks to a rock of quartz-diorite aspect and mineralogy by a process of granitization, characterized by the introduction of an alkali-felspar magmatic fluid, has recently been described by the writer from the western end of the Criffell-Dalbeattie igneous complex (1937, pp. 471–7).1 In the present paper the geochemistry of this process is considered in the light of supplementary analytical data.

The Outer Hebrides, lying off the north-west coast of Scotland, are of particular interest to the student of Pleistocene geology, on account of the grand scale on which the results of ice-action are to be seen, and because of the marine shell-beds which are to be found at the northern end of the Isle of Lewis. In the present paper no general survey ofthe glacial deposits of the Outer Hebrides will be attempted; my object is rather to drawattention to certain features of the marine fossils, as a study of the coast sections shows that a faunal sequence can be established in the Pleistocene series.

During the recent construction of a new highway linking Glacier and Yellowstone National Parks a number of deep cuttings have had to be made in the Little Belt Mountains. Some nine miles south-south-east of the once prosperous mining town of Neihart the road crosses the divide at King's Hill (7,400 feet O.D.) and, passing from Cascade County into Meagher County, starts a long and gradual descent into Sheep Creek. Along the side of the creek for a distance of several miles a series of sections reveal that the country rock is here cut by igneous intrusions with interesting contact-metamorphic effects. The mineralogy of the contact rocks has already been described by the author (l): the present communication describes the field relations and considers some problems of paragenesis.

The detailed studies on rocks of the prasinite-green schist facies published during the last decade have thrown a flood of light on the genetic relations of the various members of this facies group. References may be made to the work of Vogt at Sulitelma (l),1 Fischer in the Wippra metamorphic zone (2), Weg's studies in the Saxon Zwischengebirge (3), Turner's contributions on the Otago schists (4), and finally in this country to Wiseman's study of the progressive metamorphism of the Dalradian epidiorites (5).

It has long been suspected that the mode of development of the proximal end in Cryptograptus may differ considerably from the ordinary Diplograptid type, but the preservation of the material has hitherto been too poor to allow of a complete interpretation. Amongst the graptolites preserved in impure limestone nodules1 in the Balclatchie Shales at Laggan Burn, near Girvan, Cryptograptus tricornis is abundant, and despite the extreme tenuity of the periderm, specimens can be dissolved out with HC1 and HF, in a remarkably good state of preservation.

A brief note on this subject was published in the GeologicalMagazine, Vol. LXXII, October, 1935. In September of that year certain more detailed experiments were prepared, whose object was to afford a means of measuring the rate of accretion of tidal silt on different types of marsh in various parts of the island complex. Reference to Text-fig. 1 will show that five lines were prepared. In each case patches of fine and distinctive light brown Lower Greensand were spread over the marsh at measured intervals. Sometimes the patches, each about 2–3 feet in diameter, were put down at regular distances, but, on account of the number of small creeks and salt pans intersected by any straight line across a marsh, it. was usually more convenient to make the intervals between patches irregular. The sand was spread as a fine layer in and on the vegetation, and after it had been covered by one or two big tides, it settled down easily on the true marsh surface under the plant covering. It was then only a matter of time before it was covered by tidal silt. The sand was put down in September, 1935, and the measurements of accretion were made at the end of June, 1937.

The papers on the floras of the Carboniferous rocks, published in recent years by Dr. Emily Dix [7, 8], collectively form an important contribution to our knowledge of British Carboniferous palaeobotany. In these publications a floral classification was proposed for the Carboniferous strata of the Swansea district and an endeavour was made to apply it to other British and to foreign coalfields. The present writer, however, considers that some modification of the suggested scheme is necessary in regard to the strata included in the Yorkian Stage. Until this is done the classification will not be applicable to areas outside South Wales.

The occurrence of andalusite and sillimanite in unaltered igneous rocks is, according to the orthodox view expressed in most standard textbooks (see, e.g., Tyrrell, 1934, pp. 50, 164; Shand, 1927, pp. 62, 146; Grout, 1932, p. 230), always to be ascribed to contamination of magmas by highly aluminous sedimentary or metamorphic rocks. Having been given cause to doubt the correctness of this view by the recognition at Pyramid Hill, Victoria, of andalusite-bearing granites and aplites in which evidence of assimilation is lacking, I was then very interested to discover that the opinion has often been expressed, and evidence adduced in support of it, that both andalusite and sillimanite may be normal pyrogenetic constituents of igneous rocks.1 That is, they may under certain conditions crystallize from uncontaminated magmas. Some authors, while admitting that andalusite and sillimanite may crystallize from magmas, regard such pyrogenetic occurrences of these minerals as caused by the development of local excess of alumina, due to the assimilation of shales (e.g. Wells, 1931; Shand, 1927, p. 62). Others do not make their position clear, merely classing andalusite and sillimanite as assimilation minerals (sic), but Tyrrell goes so far as to state that they are “never of pyrogenetic oiigin” (1934, p. 50). Because of the reliance that is placed upon accessory minerals in igneous rocks as indicators of consanguinity of magmas and of the role of assimilation and other processes in pedogenesis, it is important that the status of each mineral should be thoroughly understood. In most classifications of accessory minerals andalusite and sillimanite are either classed as “contamination accessories” (Wells, 1931) or grouped with minerals that are commonly due to contamination (Wright, 1932), and Wright regards them as “of little value for correlation purposes”. Chatterjee, however, was able to use andalusite as an indicator, on the one hand, of relationship between the Falmouth and Bodmin Moor granites, both of these containing a purple variety in fair amount, and, on the other, of the distinction of these granites from those of Dartmoor and St. Austell, in which andalusite is colourless and rare. The rare, sporadically developed andalusite in the Dartmoor granite is considered by Brammall and Harwood (1923) to be a contamination mineral, but Teall suggested (1887) that the andalusite in the Cheesewring granite is probably an “original constituent” (i.e. not mechanically incorporated with the granite, as strew from xenoliths or wall rocks), and the relative abundance and uniformity of distribution of andalusite in the normal type of the Bodmin Moor granite, as exhibited at the Cheesewring (see Ghosh, 1927), lend support to this suggestion.

The present investigation establishes the following facts:—

(1) Xenoliths of vein quartz in a vogesite dyke near Kircubbin, Ards Peninsula, Co. Down, exhibit felspathic replacement-rims.

(2) The replacement-rims have developed as a result of the introduction of alk-aluminous emanations, and to a smaller extent of cafemic constituents, into the quartz xenoliths.

(3) Rheomorphic leucocratic veins extend from the felspathized rims through the lamprophyre, the veins being essentially similar in type to felspathic dykes which are associated with British Caledonian lamprophyres.

(4) Phenomena similar to those of (1), (2), and (3) are developed in the Newmains dyke, Dumfriesshire.

(5) Quartz lenticles in potash-enriched hornfels in the vicinity of the Newmains dyke exhibit similar replacement-rims, and thus bear witness to the high degree of mobility of the emanations which brought about the felspathization.

(6) Felspathization of xenoliths is shown, by reference to various recorded examples, to be a phenomenon which characterizes British Caledonian lamprophyres.

(7) The Caledonian dyke suite: lamprophyre—porphyrite—porphyry is shown to parallel the rock suites developed by processes of metasomatism and rheomorphism in individual heterogeneous intrusions.

(8) Ultrabasic types, such as hornblende-peridotite, biotite-peridotite, hornblendite, biotite-pyroxenite, and scyelite, are shown to be the most basic members of the lamprophyre suite.

(9) Chemically, the various components (a) of single heterogeneous lamprophyre dykes and (b) of the Caledonian dyke suite as a whole are shown to be expressible in terms of sialic material, alk-aluminous emanations, and cafemic emanations, the latter being directly related to the ultrabasic types listed in (8).