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.

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 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.

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.

Monelasmina, previously known only from the Frasnian of Europe, is described and figured from the Hay River formation (Frasnian) of the Northwest Territories, Canada. The specimens are referred to a new species, M. besti.

In a recent account of the geology of North-east Shetland (Flinn, 1958, Quart. Jour. Geol. Soc.) two nappes of crystalline rocks lying one above the other on a base of meta-sedimentary rocks were recognised. Comparison with the Norwegian geological literature followed by field investigations in Norway has shown many similarities with the Jotunheim area of Norway. In both areas two relatively rigid nappes were thrust one after the other over the surface of the earth to their present positions. In both areas the lower of the two nappes was emplaced first and was subjected to erosion giving rise to sediments which were deposited on the nappes (Phyllite Group of Shetland and the Valdres Sparagmites of Norway). These sedimentary groups had a similar history of formation, deformation, and metamorphism, but differed somewhat in materials because the source rocks were different, although several strikingly similar rock types are present as pebbles in both areas. The remains of the first nappe and the newly deposited sediments were overrun by the second nappe in both areas. The emplacement of these nappes gave rise to considerable deformation and metamorphism in the underlying rocks. If the metamorphic rocks of Shetland are of Caledonian age, as seems likely, then it is possible that the Valdres Sparagmites and the Phyllite Group are stratigraphically equivalent: they are certainly tectonically equivalent.

Recent work on various Triassic, Jurassic and Cretaceous radio-larian faunas from sections in northern and north-eastern Iraq, all of known stratigraphic horizon, and from elsewhere in the Middle East, confirms the existing view that as absolute indicators of age, without associated evidence, these fossils as commonly preserved are of little use, but that in local and regional problems where they are associated with other evidence they may be of considerable stratigraphical value. The genus Meyenella is not regarded as a useful indicator for the Jurassic.

Minor folds in the Gramscatho Beds at the mouth of the Helford River have two predominant trends: W.S.W.-E.N.E., and N.W.-S.E. Main folds on W.S.W.-E.N.E. axes and cross folds on N.W.-S.E. axes have sub-parallel apical planes and occur in alternate zones which trend N.E.-S.W., parallel to the strike of the cleavage. The relations between the two systems of folding suggest that they are virtually synchronous.

It is concluded that the style of folding can be explained by a unidirectional regional stress acting normal to the apical planes of the folds.

An account is given of the history of the term “eucrite”. It is shown to be very varied and hence has been a source of confusion to authors wishing to employ the word with precision, and to readers trying to understand its exact meaning. Because of the lack of agreement over the interpretation of this word, the author proposes that its use should be discontinued and the term “gabbro” utilized in its place.

The first systematic descriptions of the nosean phonolite of the Wolf Rock were given by Allport (Geol. Mag., 1871, p. 247; 1874, p. 462). Later a fuller account of the rock was provided by Teall in his British Petrography (1888, pp. 367–368). Since that time the rock has been repeatedly figured in text-books of petrography and in the light of two chemical analyses provided by J. A. Phillips (in Allport, 1871), regarded as a type example of a more sodic phonolite chemically comparable with the plutonic mariupolite. In view of the early date of these analyses, Mr. J. H. Scoon has at my request carried out a new analysis of the fresh rock, the results of which are provided in Table 1 (No. 1). This analysis reveals significant differences from the original, particularly in the potash content and shows that the rock is to be compared with the well-known phonolite of Brüx, Bohemia (Table 1, No. 3), and a phonolite from Colfax Co., New Mexico (Table 1, No. 2). The trace element distribution in the Wolf Rock has also been kindly determined for me by Dr. S. R. Nockolds (Table 1). Some additional mineralogical data which re-examination of the rock has provided may now be set down.

New discoveries have established the presence of nine ammonite zones in the Middle Jurassic beds of East Greenland. The top two are Lower Callovian; the remaining seven yield ammonites unknown from extra-Boreal provinces and are presumed to range down through the Bathonian, possibly into the Bajocian.