An outcrop of siliceous, conglomeratic grit is described on the margin of the Dartmoor granite near Woolley, and is considered to be probably of Oligocene age.

Several species of the Holothurian genus Achistrum, including three new form species, are described from the Ampthill clay of Melton, Yorkshire.

The magnetic susceptibility anisotropy of specimens of a glacial till is described and used to define a magnetic fabric. This is compared with the fabric established by small particle and stone orientation. The maximum susceptibility direction is shown to be similar to the preferred direction of the long axes of particles and stones.

Three acid breccia-bodies which are emplaced within the basaltic agglomerate of the Kilchrist vent of Tertiary age are described. They are considered to be of pyroclastic origin. Petrographic evidence which relates to the probable mechanism of emplacement of the breccias is discussed.

It is shown that in the two mineral pairs discussed the metamorphic grade can be estimated from the atomic ratios (Xa = Mg/Mg + Fe + 0·175 Mn + 0·360 Ca) in garnet and Xb = Mg/(Mg + Fe) in the other mineral. The standard error of the estimation is about one-third of the temperature range of the amphibolite facies.

Where M is the metamorphic grade on an arbitrary scale, in which the lower boundary of the amphibolite facies is at 4·2 and the upper at 5·1, and K is the distribution coefficient (Xb—XaXb)/(Xa—XaXb), then the estimating equation is M = 5·6 — 1·5 log10 K.

Five thousand feet of Upper Arenig turbidites are described with reference to their provenance and mechanism of emplacement. The turbidites were emplaced in a gently curving E.–W. trough whose width was approximately 20 miles and minimum length 50 miles. Axial and lateral derivation are recognized and it is suggested that entirely different mechanisms were responsible for the emplacement of each type.

Vermiform burrows, which are common in the Lower Greensand, can be used to estimate the relative rate of sedimentation, repeated penetration by burrowing organisms being taken as indicating slow deposition, a single undisturbed penetration as indicating rapid deposition. Application of this criterion is illustrated by reference to the Ferruginous Sands of the Isle of Wight.

Combinations of sedimentary structures in the lacustrine Keuper Marl are segregated bathymetrically. Beds deposited below lacustrine wave base are characterized by even bedding, rhythmic lamination, disturbed stratification, graded bedding, load casts, “pull-apart” structures, and oscillation ripple marks. Lacustrine beds deposited above wave base contain even bedding, rhythmic lamination, oscillation and interference ripple marks, current lineation, rib-and-furrow structure, groove casts, mudcracks, and raindrop imprints.

A marine unit in the Keuper Marl is characterized by even bedding, flat-topped oscillation ripple marks, and air-heave structures.

Comparison with sedimentary structures of other known lacustrine deposits suggests that the combination of structures in the non-marine Keuper Marl is diagnostic of lacustrine deposits. Recognition of such combinations of sedimentary structures should aid in interpreting the origin of continental sequences.

The coiling of the Liassic oyster Gryphaea is discussed and the assessment of tightness of coiling investigated. Hence Hallam's (1960a, b) statistical work on Gryphaea is interpreted and from his original measurements a highly significant increase in thetightness of coiling is demonstrated in the Gryphaeas of the higher Sinemurian horizons of Britain. The presence of a strong natural selection pressure favourable to more tightly coiled individuals of the communities is indicated, and the nature of the lineage discussed. It is suggested that recent criticisms of Trueman's work lack foundation.

The paper describes those features of the Scardroy Lewisian mass, a sheet-like body of basement rocks thrust into the younger Moine Series, which suggest that this mass was driven up through a thickness of several kilometres of Moinian rocks and inserted as a narrow wedge within the Moine succession, never penetrating the highest members of that succession. The relations of the Scardroy mass, to which most of the Lewisian outcrops of central Ross-shire belong, differ from those of the more westerly outcrops of Lewisian in the region of Glenelg where the basement rocks have been shown by the work of Clough and others to represent wedges lying between tightly-compressed synclines of Moinian rocks which form a more or less autochthonous cover. The connection between the two types of structure is discussed.

Some thousands of Australian coal samples have been studied at the Division of Coal Research, C.S.I.R.O. On the basis of these studies, the present usage of the term “sclerotinite” is considered and possible justifications for the retention of this maceral category are outlined and discussed. No characteristic differences in physical properties, form, or utilization behaviour have been found whereby sclerotinite may be distinguished from the other macerals of the inertinite group. Most of the material which has been referred to as sclerotinite is probably not fossil fungus. The “discrete body” category of sclerotinite may well represent fusinized resin bodies, while the more extensive material represents degraded plant tissue. There would appear to be no case for the retention of the maceral category sclerotinite, and alternative means are suggested of classifying for petrographic analysis material which has hitherto been regarded as coming within this category.

New genera and species of microplankton from a borehole through the Speeton Clay (Lower Cretaceous) of West Heslerton, Yorkshire, are described. One genus, two subgenera and seven species of dinoflagellates, and three species of hystrichospheres, are described, and a new family of dinoflagellates, the Muderongiidae, is set up.

Mine sections beneath the Firth of Forth at Wellesley Colliery fill gaps in the Knowledge of the strata adjacent to the junction between Middle and Upper Coal Measures. A hitherto unrecorded marine band which may formerly have been confused with Skipsey's Marine Band is now placed about 70 feet lower in the succession. A coal seam near the base of the Upper Coal Measures contains a rib of kaolin mudstone comparable with tonstein. Local reddening and alteration of coal to limestone in the Upper Coal Measures and more particularly in the upper part of the Middle Coal Measures is typical of a zone of partial oxidation beneath some major unconformity which may lie within the Upper Coal Measures or at some unlocated sub-Permian horizon above. Structureless highly-coloured clayrocks in the Upper Coal Measures, however, are regarded as primary red beds comparable with, and perhaps the equivalents of, the Etruria Marl of the English Midlands.

A brief description is given of the sedimentary features of the Aberystwyth Grits. The form and distribution of the major folds are demonstrated and their relationship to the sedimentary pattern is indicated. Thrust, wrench, and normal fault systems are discussed in relation to the stress field which initiated them. Cleavage and joint patterns are also considered. Finally the major structures of the Aberystwyth Grits are compared and contrasted with those which have developed in adjacent areas.

Pitchstones and obsidians from Arran, Eigg, and Iceland, are shown to have small but distinct differences in their major-and trace-element composition, and it is concluded that acid magma in the British Tertiary as represented by the pitchstones from Arran and Eigg maybe more variable in composition than that of the Icelandic subprovince. Fourteen new analyses are represented.

Pedicellariae, sphaeridia, and radioles associated with a specimen of Holectypus depressus (Leske) from the Bathonian of Wiltshire, are described and figured.

The Oramutia volcanics consist of a group of ignimbrites overlain by pumice tuffs, which lie in a fault formed valley on the eastern flank of the main Kenya rift valley. The presence of a dyke of ignimbrite suggests that the “claystone ” ignimbrite of this area was erupted from fissures. A similar explanation probably applies to the pumice tuffs. These volcanics are therefore the product of Katmaian type eruptions.

The occurrence of numerous washout structures in the Appin Quartzite is recorded and the criteria by which they are recognized discussed. It is concluded that these structures are reliable for the determination of the way-up of beds and that their association with current and graded bedding indicates a turbid deltaic environment of sedimentation.

Bowen's petrogenetic grid is a PT projection containing univariant curves for decarbonation, dehydration, and solid-solid reactions, with vapour pressure (Pf) equal to total pressure (Ps). Analysis of experimental data in the system MgO–CO2–H2O leads to an expansion of this grid. Three of the important variables in metamorphism when Pf = Ps are P, T, and variation of the pore fluid composition between H2O and CO2. These can be illustrated in a three-dimensional petrogenetic model; one face is a PT plane for reactions occurring with pure H2O, and the opposite face is a similar plane for reactions with pure CO2; these are separated by an axis for pore fluid composition varying between H2O and CO2. Superposition of the PT faces of the model provides the petrogenetic grid. The reactions within the model are represented by divariant surfaces, which may meet along univariant lines. For dissociation reactions, the surfaces curve towards lower temperatures as the proportion of non-reacting volatile increases, and solid-solid reaction surfaces are parallel to the vapour composition axis and perpendicular to the PT axes. The relative temperatures of reactions and the lines of intersections of the surfaces can be illustrated in isobaric sections. Isobaric sections are used to illustrate reactions proceeding at constant pressure with (1) pore fluid composition remaining constant during the reaction, with temperature increasing (2) pore fluid composition changing during the reaction, with temperature increasing, and (3) pore fluid changing composition at constant temperature. The petrogenetic model provides a convenient framework for a wide range of experimental data.

The type species of Amplexograptus is re-examined and is considered to include two distinct species. In neither of these is there any indication of a concavo-convex rhabdosome cross-section. A revised diagnosis of the genus is given and its relation to Climacograptus briefly discussed.