Available data from charnockitic rocks (including twenty-eight new pyroxene pairs fromAustralia) suggest that a major cause of variation in optically derived compositional tie-line trends of co-existing pyroxenes is related to the geothermal history of the rocks concerned. It may yet be possible to subdivide the granulite facies, and also to detect mineral instability by critical study of tie-line trends. Recommendations are made whereby mineralogic and structural studies of charnockitic rocks can be integrated to yield more reliable chemical and optical data.

Pipe-like bodies, of granitic composition, occur in certain meladiorities in Guernsey. Their average diameter is 3 inches, and they are all similarly inclined. Some connect downwards with an acid vein system; others with a discontinuous acid layer. It is considered that the pipes were formed before the meladiorite host rocks had solidified, and that their inclination was the result of relative movement between the rocks above and below.

South of Clew Bay, Co. Mayo, Wenlock strata, cut off to the north by a belt of serpentine marking the Highland Boundary, are divisible into three stratigraphical groups. The succession is repeated by a syncline overturned towards the south, which is modified by north-west cross-folds. The Wenlock strata have undergone low-grade “regional” metamorphism, in spite of which fossils have been preserved at a few localities.

Six formations, totalling 1,210 metres and grouped as the Oslobreen Series, are dominantly of dolomite and limestone often with evidence of discontinuous deposition. They contain a Lower Cambrian and a Canadian fauna. The succession is similar to those of this age in N.W. Scotland, where a revised thickness is given, and in E. Greenland. A new species of Canadian trilobite (Hystricurus) is described in the Appendix.

The confusion that has arisen over the interpretation of the D2—D3 boundary is analysed and a new definitive section of the Upper D Beds is given.

The recent suggestion that natural selection of random mutations is inadequate to account for the major features of evolution is rejected. The pattern of evolutionary development in most major groups, the phenomena of extinction and replacement, the rates of appearance of new major taxa, the continuing vitality of the evolutionary process, the overall randomness of evolutionary history, containing directional change within individual lineages, the nature of natural selection, and the geologic evidence for environmental instability are examined. All suggest that natural selection and random variation are adequate to account for the major features of evolutionary history.

Two short seismic refraction profiles have been shot across the former valley of the River Teifi, above and below Cardigan, with the object of determining the depth to the rock floor. This was found to lie 75 feet below O.D. at Castle Malgwyn, near Llechryd and 107 feet below O.D. at the present estuary. These figures are consistent with the glacial history of the valley indicated by the geological evidence.

The Lower Old Red Sandstone deposits of Ekmanfjorden belong mainly to the Lykta Division, but pale sandstones with Giganthaspis representingthe Kapp Kjeldsen Division also occur in the core of what is probably a N.-S. striking anticline. The lower beds of the Lykta Division are soft, dull and silty and not very fossiliferous; above them are some 1,100 feet of sandstones and conglomeratic beds alternatingwith shales or marls. Locally abundant vertebrate remains include the guide fossil Doryaspis. Various sedimentary structures suggest rapid deposition on a broad shallow delta front.

Volcanism began in South-east Devonshire with the extrusion of keratophyric tuffs in the Lower Devonian. The majority of extra ves in the Middle and Upper Devonian are basic spilites but there are intermediate varieties. Volcanism in the Middle Devonian was local and in the Ashprington area appears to have been continuous throughout the epoch. At the beginning of the Upper Devonian keratophyric crystal and vitric tuffs were extruded in the Dartington area. Later in the Upper Devonian the Chipley pillow lavas were extruded: it is shown that these lavas were widespread and may probably be correlated with similar lavas at Pentire Head in North Cornwall. The final phase of volcanism is represented by the intrusion of swarms of sill-like bodies of spilitic dolerites in Upper Carboniferous times. Intrusive and extrusive rocks are distinguished, mapped, and classified petrographically

An attempt has been made to show that basic magma is associated with vertical and not with folding movement, that basic intrusions take the form of those characteristic of unfolded regions and of relatively high levels and that differentiation in situ is common.

It is argued that basic magma is emplaced in the orogenic belts as flows and typically non-orogenic intrusions during the geosynclinal or sinking phase of the orogenic cycle, that rocks of the appinitic suite, which commonly occur as stocks associated with granodiorites, are formed from these non-orogenic basic rocks by a process of hybridization during a subsequent folding phase, but that no further basic magma is introduced during this phase.

It is suggested that the terms Non-orogenic Association and Orogenic Association might replace Volcanic Association and Plutonic Association to indicate the relation of basic and acid magmas to their tectonic environment.

Sedimentary structures in the lowest sub-division of the Torridonian of Skye are described and figured. Trough cross-stratification of the type known as festoon bedding is widely developed in the coarser grits. Finer-grained sandstones show curly-bedding structures due to post-depositional disturbances. Siltstones and mudstones are characterized by a fine lamination and by such structures as ripple-marks, minute graded bedding and desiccation cracks. The orientation of cross-laminae in the festoon-bedded grits indicates that the currents depositing these rocks flowed towards the north-east or east.

Mudstone inclusions in graded greywacke-conglomerates of Salopian age from the Slieve Bernagh Mountains, Co. Clare, are considered to have been formed by fracture of the conglomerates in the course of slumping shortly after deposition and the infilling of the resulting cavities by mud derived from the underlying beds. The attitudes of the inclusions and of associated pebble imbrication suggests that slumping took place on a slope with a northerly inclination of 10°.

The English Bathonian contains a rich foraminiferal fauna composed largely of Lagenidae. The succession of foraminifera is as yet only partially revealed, but some faunal changes between the Lias and Bathonian are apparent, and four faunules have been distinguished in the Bathonian. In Dorset and the vicinity of Bath the faunules occur in the same order of superposition. In comparing the English Bathonian foraminifera with those in the German section the present data suggest that a number of species range higher in England than in Germany.

The property of liquefaction of certain confined, water-logged, unconsolidated sedimentary layers is considered to play an important part in the development of much of convolute folding. Lateral intrastratal laminar flow of liquefied beds, according to flow patterns mainly determined by the distribution of parts of the layers that have remained solid, appears to account satisfactorily for internal folding. Although intra-stratal flow, which can result from a number of causes, may considerably deform the stratification planes of a liquefied layer, there is neither lateral shortening nor a notable change in the thickness of the bed.

A new fossiliferous section in the Coralline Crag of Suffolk is described, and its fauna is analysed as a clue to the conditions under which these beds were formed; in particular, the theory that the temperature of the Crag sea was affected by the alternate breaching and closing of land-bridges to the north and south of the North Sea area is considered unnecessary to account for the facts as seen in the field. Further, the Coralline Crag is correlated with the Astian formation of the Mediterranean, and reasons are brought forward to show that the supposed “Boytonian” Zone of the Coralline Crag does in fact not exist.

The lophophores of spire-bearing fossil brachiopods (Spiriferoidea and Atrypoidea) arereconstructed by homological comparison with living brachiopods. It is inferred that all spiral brachidia supported simple spiral lophophores. For each type of brachidium, only one arrangement of the spirolophe could have created an efficient filter-feeding system. The water would have entered the mantle cavity laterally and been ejected medially; but would have been filtered between the whorls of the conical spiralia either outwards (e.g. Atrypa) or inwards (e.g. Spirifer). These are the only possible alternatives: it is probable that both systems were evolved more than once.

An ambiguity in previously published hornblende orientation data is pointed out and illustrated by measurements on an epidiorite. A method is proposed of differentiating in certain cases between (a) a fabric derived by crystallization of hornblende under stress and (b) that derived by alignment of pre-existing hornblende prisms.

The heavy mineral suites of the Trias, Rhaetic and lowermost zones of the Lower Lias in the Vale of Glamorgan of South Wales are described. The northerly coastline of the Mesozoic sea, roughly coincident with the present-day periphery of the Coalfield, consisted mainly of Carboniferous Limestone and in places, the Old Red Sandstone and Millstone Grit. The mineral assemblage at any particular point in the littoral zone was determined largely by the nature of the outcropping rocks of the coastal mainland, the derivation of detritus being very localized. Within this zone some degree of gravity sorting of the detritals occurred, this implying a relatively steeply inclined coastal sea-bed. An off-shore current carried detritus from the Armorican land-mass of Britanny and granite of South-West England to this area where the detritals were dispersed thinly throughout the locally derived sediment.

A succession of Jurassic sediments is shown to have been metamorphosed in contact with a Tertiary microgranite. The meta-morphic features of the three main lithological groups of the sediments are described and the conclusion is reached that in addition to simple thermal metamorphism, which is apparent in most of the rocks, the rocks nearest the microgranite have been permeated by aqueous fluids containing K2O, Na2O, MgO, FeO and Fe2O3.