The following description of new genera and species of Lower Ordovician Cryptolithids is the result of a stratigraphical and palaeontological investigation of the rocks in the Llangadock-Llandeilo district, Carmarthenshire.

Discovery of a shallow oilfield in Triassic rocks in a fenland area west of Formby, as described by Lees and Taitt (1946, pp. 307–11), led to an attempt to determine the nature of the local Carboniferous rocks, which were regarded as the most likely primary source of the oil found in the Trias.

Agmatite was one of the new descriptive terms introduced by the late Professor J. J. Sederholm in connection with his life-long study of the Finnish migmatites. He applied this name to a group of migmatites which present an appearance that has suggested the terms “eruptive breccia” and”intrusion breccia”, but agmatite has a very different genesis from that connoted by these terms. Sederholm (1923, p. 117) wrote: “As these migmatites consisting of fragments of older rocks cemented by granite are genetically and petrologically very different from many of the rocks that have been called eruptive breccias many of which are volcanic rocks, the author proposes to designate this group of migmatites as agmatites (from ἂγμα, fragment).” The elaborate drawings and illustrations to be found in Sederholm's Memoirs (1923, 1926), however, give a much clearer idea of the appearance presented by these rocks than any written description.

The objects of this paper are to supplement previous descriptions of the coast sections of the New Red Sandstone from Exmouth to Oddicombe, and to discuss views of the origin of the rocks as stated in the following quotation from the revised Torquay Memoir (Ussher-LIoyd, 1933, p. 105): “It is generally accepted that the lower New Red Sandstone breccias result from continental conditions, in which the extremes of temperature and recurring torrential rainfall operated on the bare slopes of a mountainous region, to produce diluvial fans, similar to those now being formed in the mountain valleys of Kashmir and Persia, The Dartmoor granite no doubt once formed an elevated dome and from this high ground, much higher and more extensive than at present, torrents flowing in a general easterly direction would produce gravelly accumulations, composed largely of the angular debris of formations then exposed. These accumulations may in part have been swept into a lake and there mixed with, or alternated with, beds of sand deposited under normal conditions; wind-borne sand may also have been blown from the desert into this lake or inland sea.” The term “diluvial fans” was introduced by Lloyd into the revised memoir, obviously without any reference to Pleistocene glacial deposits or the Deluge of Noah, as might be suspected from the use of this old word “diluvial”. “Alluvial fans” is preferred here and no evidence has been found of glacial action at any time.

The ostracods described in this paper have all been obtained from the Goniorhynchia boueti bed, as exposed at the little peninsula known as Herbury (“Herbeyleigh” in some of the older geological literature), near Langton Herring, some five miles to the west of Weymouth. The bed is at sea level at the north-west corner of Herbury, and is there about one foot thick. It is from this point (national grid ref. 30/610810) that the samples were taken for the separation of microfossils. Polyzoans, baby brachiopods, foraminifera, “vertebral” ossicles of ophiuroids, radicles of echinoids and minute gastropods, make up as diverse and interesting an assemblage as that formed by their better known macroscopic contemporaries.

Since the beginning of the century Carboniferous corals have been intensively studied throughout the world, and in this paper our resultant knowledge of their distribution and the sequence of faunas is outlined. The lower limit of the Carboniferous is taken to be at the base of the K zone of the Bristol sequence, and the upper limit at the base of the Russian Kungurian stage, in conformity with the principle of priority of nomenclature. The period is thus a long one including the Russian Artinskian, while the Permian is relatively short. Many recent writers, e.g. Dunbar (1940, 1942), adopting criteria other than priority of nomenclature, have extended the Permian downwards to incorporate greater or lesser amounts of the Carboniferous.

(1) The range of variation in the external characters of the rhynchonellids examined is illustrated by means of graphs and scatter-diagrams.

(2) The three-variable scatter compares directly the proportions of thickness, breadth, and length, and defines the assemblage as adequately as several scatters which relate only pairs of variables. A close relationship is shown to exist between the three-variable scatter in which the positions of specimens are mathematically determined and the scatter in which the specimens are placed according to general appearance.

(3) The three-variable scatter, when considered with size-groups, indicates that with growth, breadth and thickness increase more rapidly than does length. All the scatters indicate that proportionate thickness Varies to a greater degree than does proportionate breadth or proportionate length.

(4) The sample, being random, is probably nearly representative of the goniorhynch rhynchonellid fauna of the Boueti Bed at Langton Herring. The stratigraphical value of the work, however, can only be proved by examination of assemblages from other localities and horizons.

(5) Since the scatters show that all gradations occur between the extreme variants, the forms behave as though belonging to a single homogenetic community. It is recognized that internal characters may in due course be found to show discontinuity in their variation, but on present evidence it appears that only one species is present.

Among a batch of reprints recently received from Professor Lugeon (1946) is one dealing with the above subject; it is of more than local interest as it prompts comparison with certain phenomena in this country.

The Ashgillian as the name for the uppermost series of the Ordovician system was proposed by Marr in his address to the Geological Society in 1905, and subsequently further justified by him in a paper in the Geological Magazine in 1907.

In this paper the writer deals with certain mineralogical and textural features found in the Moine and Sub-Moine Series of western Scotland, viz. garnet-zoisite calc-silicate ribs, non-garnetiferous epidotic calcsilicate ribs, sutured (crenulate) quartz-mosaic, foliation oblique to folded bedding, and the presence of abundant yellow epidote and of spots of haematite. The garnet-zoisite calc-silicate ribs have been claimed by Dr. Richey and Professor Kennedy as diagnostic of parts of the Moine Series. For the non-garnetiferous epidotic calc-silicate ribs, which have not previously been described, the name “calc-silicate ribs of Arnipol type” is suggested. These ribs occur in adjacent groups of rocks that have been mapped with the Lower Striped Schists and the Lower Psammitic Group of the Moine and with the outermost psammitic zone of the Sub-Moine.

A large part of Central Sutherland is occupied by an injection complex in which rocks of the Moine Series are associated with much granitic and pegmatitic material. These migmatitic Moinian rocks have reached a higher grade of metamorphism than those which occur outside the injection complex. One feature characteristic of the high-grade migmatites is the presence of sillimanite in many of the pelitic and semi-pelitic rocks. Near the village of Kildonan, ten miles north-west of Helmsdale, sillimanite is not only abundant in the country rock, but occurs also in many pegmatitic and aplitic veins. The field and microscopic evidence shows that this mineral was formed as a result of metasomatic activity at a late stage in the history of the injection complex, when the general metamorphism was already on the wane. The sillimanite seems to have no direct connection with the conditions of regional metamorphism. It was formed under the influence of pegmatitic solutions. In view of the common use of this mineral as an index of the grade of regional metamorphism, it is of interest to describe the evidence on which the above conclusions are based.

Among the most controversial problems of British geology are those concerning the metamorphic rocks which make up the greater part of the Scottish Highlands. The writer, in common with many geologists whose work has brought them into contact with the region, has long felt that the discussion and solution of these problems would be greatly facilitated by a nomenclature less involved and more consistent than that at present in use. A simplified nomenclature, moreover, would do much to stimulate and hold the attention of students and general readers.

While conducting elementary field-classes in the Ingleton area it is not possible to show students any convincing grounds for separating the Ingletonian Series from the Coniston Limestone above. The field-evidence which so strongly impressed Hughes, Goodchild, Gunn, and Green, and which apparently convinced Aveline against his will, still exists. In all three streams the highest beds of the Ingletonian are slates, which might be thought to show a gradation into the Coniston Limestone above, and the dip and strike of the Coniston Limestone appear closely similar to that of the near-by Ingletonian. Against these tangible facts arguments based on petrological similarities, even the evidence of the Neptunian dyke, are apt to seem slightly strained. Accordingly, during a field-excursion I suggested that an attempt be made to excavate the actual junction, and during the summer three students of Imperial College, Messrs. R. W. D. Elwell, G. J. H. McCall, and A. F. Trendall, have succeeded in laying it bare. To their enthusiasm and hard work the success of the attempt is wholly due. Owing to the kindness of Mr. W. S. Worthington, of Ingleton, the new exposure will be left open indefinitely.

In this magazine for January, 1938, there appeared a short note on the rate of sedimentation in the salt marshes of Scolt Head Island. The records then only covered two years. In a note in the Trans. Norfolk and Norwich Nat. Soc., 15, 1939, 41, some additional readings, covering four years, were published and analysed. This summer (June, 1947) I was able to measure the accretion again after a further interval of eight years, so that we now have rates and averages for two, four, and eight years. Unfortunately the line on Aster Marsh was partly destroyed during the war when it regrettably formed part of the target area for artillery fire.

The metamorphism of the Durness dolomite horizons in the aureole of the Beinn an Dubhaich granite of Skye has long provided one of the best known examples of dedolomitization and progressive thermal metamorphism of siliceous dolomites recorded in the literature. Harker's study (1904) concerned itself primarily with assemblages regarded as derived without notable accession of material during metamorphism and the occurrence of products of metasomatic origin at the contact of the granite has hitherto received but little notice in print. Yet as long ago as 1897, Geikie had written of this contact: “… the most abundant and interesting deposits are metalliferous. Fragments of a kind of ‘gossan’ may be noticed all along the boundary line of the boss, and among these are pieces of magnetic iron ore and sulphides of iron and copper. The magnetite may be seen in place immediately to the south of Kilbride. A mass of this ore several feet in diameter sends strings and disseminated particles through the surrounding granophyre and is partially coated along its joints with green carbonate of copper” (Geikie, 1897, p. 384). It is of interest to note further that a record of “a mineral resembling humite” from this same contact is made in the Annual Report of the Geological Survey for 1896 (1897).

Belemnites are common throughout the boreal province of the Upper Cretaceous Series of Eurasia occurring at practically all horizons of the so-called Senonian stage (in the broader sense) nearly everywhere in this province; often they are the only group of fossils to be met frequently enough to be used for stratigraphical purposes. Despite this there have so far been relatively few efforts to use the Upper Cretaceous belemnites as zone-fossils, with the exception of some Actinocamax and Gonioteuthis species. The probable reasons for this regrettable neglect have already been mentioned in a previous paper (e.g. Jeletzky, 1946, pp. 87–90). Our researches, the results of which have till now only partly been published (e.g. Jeletzky, 1940, 1941, 1946) have shown that the Upper Cretaceous belemnites occur relatively frequently, and in the same stratigraphical order throughout the whole Eurasian boreal province and are in fact excellent guide fossils.

Since the publication in 1880 of Nicholson and Etheridge's monograph of the Ordovician and Silurian fossils from Girvan, no further work has been done on the coral faunas of that region. While engaged on a revision of the rugose corals as a whole, I have studied a part of the Gray Collection in the British Museum (Nat. Hist.), of which the present article is an outcome. I am grateful to the keeper of the Department of Geology, and to Dr. H. D. Thomas for the loan of material and for the kind interest shown in my work, and to Dr. Stanley Smith for his valuable criticism and advice. This work was mainly carried out in the Sedgwick Museum, Cambridge, and I take the opportunity to express my thanks to Professor W. B. R. King and Mr. A. G. Brighton for facilities for study. Dr. H. D. Thomas and Dr. O. M. B. Bulman both kindly read the manuscript.

During the Easter Field Meeting of the Sedgwick Club, portions of the Neptunian dyke at Hazier Hill, near Church Stretton, were collected and brought back to Cambridge for further examination. The material consisted of a buff-coloured, sandy mudstone with scatters of facetted pebbles of quartzite and igneous material, including weathered rhyolite, up to a centimetre in diameter. The material proved to be richly fossiliferous and the following fauna was obtained which, we believe, throws some light on the age of these sand-filled fissures :—

In the discussion on a paper read recently by A, G. MacGregor on Scottish Carboniferous volcanicity,1 one of us, speaking on behalf of both, raised some points concerning the nomenclature of magma-types which we feel are worth amplifying. The points at issue concern firstly the use of the terms “tholeiite” and “olivinebasalt” when applied to fundamental magmas, and secondly the propriety of referring to the suites of rock-types supposed to be derived from them as “calc-alkali” and “alkali” respectively.

During the war a large new quarry was opened in the Longmyndian rocks of Haughmond Hill, Shropshire. It is near the south-east edge of the hill, to the west of the road running north from Upton Magna and one mile from the village. On the sketch-map in the Shrewsbury Memoir (p. 58) two arrows are shown, at about this locality, recording dips of 50° in a south-easterly direction. I was told that there was a very small quarry here before the large quarry was excavated. The present quarry is even larger than that near Haughmond Abbey (Shrewsbury Memoir, p. 48), on the north-west side of the Pre-Cambrian outcrop, and the two quarries offer extensive and splendidly displayed exposures of Longmyndian rocks, one in the coarse-grained Western Longmyndian and the other in the fine-grained Eastern Longmyndian.