Some of the nodules described are similar to trace-fossils described by Donaldson and Simpson and some ichnofossils described by Seilacher, but many appear to be structures produced by sedimentary boudinage. These do not seem to be a result of organic or concretionary action. It is suggested that currents deposited thin bioclastic calcarenites with interbeds of calcite silt, and that crinoids and coral patches developed only sporadically during deposition. A few scavengers reworked the bioclastic calcarenites and calcite silt layers thus forming the trace-fossils; many of the irregular-nodules, however, were probably formed by differential compaction and segregation in the calcite silt beds, and may represent sedimentary boudins, which are relicts of former layers.

A new description of “Didymograptus” fasciculatus Nicholson, 1869, is given on the basis of specimens from the Skiddaw Slates (Zone of Didymograptus bifidus) some of which are preserved in relief. The uniramous rhabdosomal form is confirmed. The presence of prothecal folds indicates that the species belongs in the family Sinograptidae Mu, 1957, and adoption of the generic name Nicholsonograptus, proposed by Bouček and Přibyl (1951) with “ D. ” fasciculatus as the type species, is recommended. The possibility that Nicholsonograptus fasciculatus is an intraspecific variant of Holmograptus lentus (Törnquist, 1911) is discussed.

Structures in the Upper Purbeck Beds at Peveril Point, Swanage, Dorset, are described. Interpretation of the overall structural pattern has been attempted by constructing a three-dimensional model of the Broken Shell Limestone surface, upon which the more complex folding of the shales and marbles has taken place. The regional setting of the structures is discussed.

The character, horizon, and extent of ten kaolin tonsteins occurring in the Westphalian strata of the North Staffordshire Coalfield are described, and four additional horizons considered worthy of further study, when this is possible, are noted. The value of these kaolin tonsteins in correlation, and the possibility that they may fall into two groups having different origins, is briefly discussed.

Eighteen potash felspars from the potash felspar gneisses of the Connemara migmatite belt have been partially analysed and the associated plagioclase optically determined. Comparisons have been made with seventeen similar felspar pairs from the Galway Granite. Albite components are expressed graphically in an attempt to illustrate sodium distribution between associated felspar phases. On such a plot it is possible to contrast the “magmatic” felspars of the Galway Granite with those of the migmatitic gneisses; the separation of the two fields being a function of total rock chemistry. Crystallization temperatures have been determined by the two felspar method and the range 460 to 480° C. is thought to represent retrograde amphibolite conditions in the migmatitic gneisses, while petrographic evidence supports 550° C. as the temperature of amphibolite facies metamorphism in these rocks. Triclinicity measurements have also been made on the analysed potash felspars.

As a result of magnetic, seismic, and gravitational studies it has been possible to describe the nature of the boundaries of the Mountsorrel granite massif in more detail. Confirmation has been found of faulting postulated on other grounds; and also it is shown that there is no substantial underground extension of the granite beneath the surrounding Triassic countryside to the west of the outcrop.

One of the internal contacts of a doleritic intrusion, Co. Donegal, is lined with large augite dendrites. The habit is revealed by parting on a median zone of chlorite which is regarded as an altered exsolution feature. It is suggested that an initial platy dendrite grew, in response to undercooling, as a metastable phase with the composition and structure of a high-calcic pigeonite. A later overgrowth of augite preserved the delicate crystal against destruction.

Three large pipes of brecciated Torridonian sediments set in matrices of calcite and calcareous mudstone occur on the island of Raasay. Previous work has shown that these structures may be due to explosive fumarole activity during the Tertiary volcanic episode. A recent study of the Torridonian stratigraphic succession has made it possible to demonstrate that there was considerable variation in the amount of vertical collapse of the local country rock caused by the explosions. In one vent local fracturing and brecciation took place with no downward movement; in another it is possible to show that Torridonian boulders tumbled at least 350 metres down into the throat of the fumarole. The amount of vertical collapse increases from vent to vent southwards towards the Cuillins volcanic centre.

These vents are of particular interest for two reasons. Though clearly of volcanic origin they contain no volcanic material. Secondly, the carbonate matrix of analogous structures is generally believed to be due to the hydrothermal solution of underlying limestone beds. The latter are absent in these examples and the carbonate material seems to be solely of volcanic origin.