The form of a brachiopod shell is the product of the rates of growth operating at all points on the valve edges during successive stages of growth. Shell form is analysed here in terms of these rates of growth, the rate at each point being resolved into component rates. If the antero-posterior growth gradients are linear, the shell is rectimarginate; if non-linear, the lateral commissure is “flexed” throughout ontogeny. Localized anomalies in the growth rate may modify either of these basic growth patterns at any stage in ontogeny. They produce deflections in the commissure, and these generally produce deformations in the valve surfaces (e.g. folds, sulci, costae). Two major varieties of external hinge structure are defined: strophic shells have a true hinge line and may also have interareas; non-strophic shells have no true hinge line but may have palintropes. The implications of this formal analysis are examined in relation to the systematic description of the shell form.

Bouguer gravity anomalies have been determined at seventy-nine stations on Alderney, Guernsey, and Jersey. On Alderney the anomalies are clearly dependent on the nature of the outcropping rock-types, and permit approximate values for the thickness of two outcropping rock masses to be obtained. On Guernsey the anomalies are not closely related to the surface geology, and suggest that the north-eastern coastal area is underlain by a body of dense rock, possibly of ultrabasic composition. The anomalies on Jersey indicate that the sedimentary rocks of western Jersey are underlain at no great depth by rock of density comparable to that of granite. In eastern Jersey the dominating feature of the anomalies is a pronounced “high” centred near Grande Charriére. It is shown that this feature is most reasonably considered to be the effect of a large buried gabbro intrusion.

A deep seated flow of geoplasma (bathyrheal underflow) subjected crustal blocks to recurring horizontal movements causing north-east trending faults, shearing along anticlines and rotation of the separate crustal blocks. These movements produced extensive faulting and shattering in the South Alligator River area and north of Katherine, providing suitable loci for uranium mineralization. The mineralization occurs as a late phase open fissure filling and two types occur, (i) the nickel–cobalt–native silver type, and (ii) the quartz–pyrite–galena type. These characteristics provide a guide for future prospecting for uranium in Australia.

The scheme currently used in East Africa for Pleistocene stratigraphic correlation is bases on climate. This basis is thought to be undesirable because it consists of second-order concepts rather than of primary, objective units and because its unconventional character inhibits correlation between East Africa and other regions. Furthermore the conceptual sequence of pluvial and interpluvial Pleistocene climates is not fully supported by the field evidence described thus far. Local support exists for the Gamblian and post-Gamblian and post-Gamblian wet climates, and at one locality a wet phase of pre-Gamblian age is admissible. The other units of the current scheme require factual support before they can be accepted. It is suggested that a more conventional basis of Pleistocene correlation in East Africa is desirable.

A review is given of the geology of the islands of the Scotia Arc. The provenance of the sedimentary materials is considered and it is concluded that the islands probably represent areas with a crustal structure of a continental type. The crustal structure of the Scotia Sea area is briefly compared with that of the Caribbean.

Carbon replicas of coccoliths examined under the electron microscope reveal structural details which are invisible under an oilimmersion microscope, but are essential for a systematic study of these minute bodies. In an appendix, one new genus and six new species are described. Some of these appear to have a limited vertical range within the English Chalk.

An assemblage of microplankton from the Cornbrash of Yorkshire is described. It consists dominantly of dinoflagellates, including three new species of Gonyaulax and one new species of Pareodinia. A relatively small number of hystrichospheres are present, including new species of Baltisphaeridium, Cymatiosphaera, and Pterospermopsis. The character and significance of the assemblage are discussed.

The Abitau Lake area, N.W.T., chiefly consists of medium-to-coarse-grained quartzo-feldspathic gneisses. Many of these are granoblastic, presenting little or no microscopic evidence of deformation. Others are highly tectonized and foliated varieties that sometimes form pseudomigmatites easily mistaken in the field for true migmatites formed by lit-par-lit injection of pink granite into more basic grey gneiss. The last, however, are found after detailed examination to be granitic rocks that owe their misleading appearance and distinctive fabric to deformation during isochemical amphibolite fades metamorphism. Surprisingly they are not mylonites. Their fabric, like that of the other foliated gneisses is dominated by the parallelism of dark minerals and elongated quartz crystals. It resembles that of typical European granulites and often seems largely due to compression acting in a direction normal to the foliation plane with little or no transport in that plane. Tectoniza-tion did not promote the formation of myrmekite or microperthite but may have assisted to some extent the production of epidote from hornblende in certain specimens.

A re-examination of Hettangian and Lower Sinemurian oysters has led to the rejection of Trueman's hypothesis on the evolution of Liostrea into Gryphaea. Gryphaea assemblages from two horizons in different parts of Britain have been subjected to bivariate and size frequency analysis. The only detectable difference is a slight size increase up the succession. No “gryphaeoid” trend is discernible in Liostrea up the Hettangian succession and the change to Gryphaea is in consequence abrupt. All the oysters of Trueman's series are referred to what are considered to be two different Linnaean species.

On the eastern side of the Mount Lofty Ranges of South Australia, impure marbles and calc-silicate rocks characterized by assemblages rich in scapolite and pyroxene have been formed on a regional scale by high grade metamorphism of limestones and calcareous shales. It is suggested that this metamorphism is essentially iso-chemical and that even chlorine in the scapolite (Me 55[60) could have been derived from the original sediments.

A secondary paragenesis consisting of epidote, actinolite, and calcite at Tungkillo and epidote, actinolite, calcite, and garnet at Milendella, is the result of late metasomatism and reaction associated with the formation of granites, migmatites, and veined gneisses. At Tungkillo, outside the sphere of granite activity, the secondary, retrograde assemblage is due to limited metasomatism chiefly involving the introduction of water, whereas at Milendella where marbles and calc-silicate rocks are intimately associated with granitic rocks, reaction and metasomatism giving rise to the secondary minerals has been more intense. Here garnet of the andradite-grossularite series has developed.

Boudinage occurs with great regularity in parts of West Cork. The principle break-up of competent beds is into boudins with the separation parallel to the dip of the bedding, but where the exposure permits examination in three dimensions it can be seen that incipient boudinage is developed with separation parallel to the strike of the bedding. The structure is shown to have originated after the main phase of folding by horizontal forces acting on steeply inclined beds. Some unusual features are described.

The complex described is composed of basic to ultrabasic rocks, ranging in composition from hornblendites, through meladiorites, to diorites. It is surrounded by the Bigga Granite, which has an intrusive relationship with the basic complex. The nomenclature of these rocks is discussed, and detailed petrographical descriptions, together with modal and chemical data, are given. It is suggested that the original rocks of this complex were probably of gabbroic composition, and that they subsequently assimilated and hybridized to give rise to the observed rock types.

A reversed seismic refraction station and some cores taken on the Dogger Bank, in the North Sea, are described. The absence of compacted sediments within the bank and the finding of only glacial or post-glacial sediments at its surface strongly suggest that the bank is a large moraine.

The various mechanisms which could cause oblique slip faulting are briefly reviewed. It is thought that such faulting may frequently arise from the existence of preferred planes of fracture within the rocks. The dynamics of this mechanism is studied in some detail and an expression is obtained for the first direction of slip within the plane under the influence of a general stress system of given orientation it is found that the initial slip may occur in any possible direction within the plane, the direction depending on the relative values of the three principle pressures. The theory suggests that when a pre-existing fault is subjected to a reorientated stress system (typical or rotated) the movement after fracture will usually be oblique. In conclusion, the general implications of the theory are discussed.

A unique chert nodule, bowl-shaped, ten feet in diameter and three feet deep, with a mass of crystalline calcite in the bottom, occurs in the lower part of the Hawes Limestone at the base of the Yoredale Series. The overall peculiarities of the nodule require an origin after consolidation of the enclosing work.

The basis for Mr. Hallam' rejection of the hypothesis on the evolution of Liostrea into Gryphaea is briefly examined and is shown to be inadequate. For Liostrea real evidence is lacking. For Gryphaea the evidence, though copious, is unsound for it is based upon an improper treatement of his collections. Moreover, the features he measures are not sufficiently significant and the reader is left in considerable doubt as to the actual range of his measurements. His aspersion upon previous workers in this field is entirely unjustified.

The possibility of the Southern Upland Fault of Scotland continuing to the west coast of Ireland is examined critically. No post-Carboniferous faulting has occurred along this line in Ireland. It cannot be connected with any major fault occurring in the Lower Palaeozoic rocks of County Mayo or County Galway; and there is no evidence that it continues as a structural line to the south-west of Carrick on Shannon.

The major stratigraphic divisions of the Carboniferous rocks of Devon and Cornwall are characterized and new terms suggested to replace those of W. A. E. Ussher. It is shown that there is in South Devon and Cornwall a major unconformity separating an uncleaved group of post-orogenic Carboniferous strata (Ugbrooke Group) from underlying Devonian and Carboniferous with slaty cleavage. It is argued that the Ugbrooke Group is younger than any strata hitherto thought to be present in the Carboniferous of South-West England, and that the major orogeny is either Malvernian or Asturic in age.

A basic gneiss in Ghana is traversed by light veins which are considered to have originated by replacement because gneissic mineral banding persists through them. Veins make up to 10 per cent of the rock over hundreds of square miles. It appears that a very large amount of material has been transported through the basic rocks without destroying their gneissic structure.

Mines near Culross, in Fife, have traversed a vent of Upper Limestone Group (Namurian) age at levels estimated to be 150 to 250 feet below the contemporary surface. The vent-filling comprises a central basaltic tuff, and a marginal lithic tuff derived entirely from the Carboniferous sedimentary rocks. A sill-like body of lithic tuff has been intruded beyond the vent margins. In sediments outside the vent post-volcanic subsidence has generated small faults; these become flat-lying or undulating where they traverse mudstones and siltstones that are inferred to have been incompletely indurated at the time of the subsidence. The volcanic and post-volcanic processes are discussed in the light of Cloos' interpretation of Swabian volcanism.