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.

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 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 area yields marbles, schists, and quartzites, probably of Hecla Hoek age, a series similar in lithology to those in the Kongsfjorden region. Their structure and metamorphic condition fit in with the general picture of Caledonian trend and of increasing orogenic activity westwards. Later faulting along the western edge of a graben has broken this ground up into independent blocks as witnessed by the disposition of the Devonian conglomerates. The youngest rocks are a southerly outlier of the plateau basalts best seen around Woodfjorden, remnants of at least two flows are preserved, both of olivine basalt rich in olivine phenocrysts and carrying inclusions of a more alkaline rock type.

A sedimentary formation beneath the Bray Series is found to have an extensive outcrop in southern Co. Wicklow. Evidence is given of the Pre-Cambrian age of both series. They are exposed in a Caledonian anticlinorium, which has been cut by thrusts and high-angle faults, but they had suffered strong orogenic deformation and prolonged erosion before the unconformable deposition of Lower Palaeozoic strata.

A small plug-like body is made up of an intrusive breccia contained within a ring of felsite. The felsitic matrix of the breccia is of composite origin and certain textures may indicate contemporaneous breaking of crystals. Attention is drawn to the association of this diatreme with the suite of felsite, hornblende lamprophyre, and hornblendite intrusions clustered around the diapiric pluton of Ardara.

To account for a type of rhythmic unit found in the Bushveld complex of South Africa and probably in other layered intrusions, a hypothesis is put forward dependent on the different powers of crystal nucleation from supersaturated magma. It is suggested, for example, that the three common primary precipitate minerals, chromite, bronzite, and bytownite nucleated in this order which is probably dependent on the differing complexity of their crystal structures and that the common rhythmic unit, beginning with chromitite, passing upwards into bronzitite and ending with a bytownite-rich rock is the result of these crystals accumulating successively at the bottom'of the liquid.

In East Norfolk, boreholes have revealed the presence of a northern and a southern clay bed in the Crag. These lie at different horizons and have been linked to clay exposures previously correlated with the Chillesford Beds of Suffolk. It is concluded that a clay facies is developed at two main horizons in the Crag in Norfolk.