The usage and synonymity of the names of some olivine-bearing feldspathoidal extrusive rocks is discussed. In the nephelinic rocks it is suggested that the terms nepheline-basalt and olivine-nemafite be abandoned, and that the use of olivine-nephelinite be continued. A similar recommendation is made for other feldspathoidal rocks.

Echinocyamus woodi Currie from the Miocene of Kenya is reexamined and considered to be conspecific with Fibulina gracilis Tornquist and Fibularia voeltzkowi Tornquist. This echinoid is a fibularid, not a laganid.

A number of acid plutonic xenoliths from the volcano Surtsey are described, along with fine-grained rock fragments, consisting chiefly of anorthitic plagioclase and tridymite. The chemistry of the xenoliths indicates a compositional pattern from tonalitic to pyrometamorphic types. A hypothesis is put forward that the tonalitic xenoliths have undergone partial fusion during transport to the surface in the basaltic magma, and the removal of a salic liquid from granitic xenolith into the magma has resulted in the formation of a residue of anorthitic plagioclase and tridymite. Granitic xenoliths from other parts of Iceland, and their fusion products, are also described.

A petrographic study of the sediments of Ghazij Formation, supplemented by field observations, has been made with a view to studying the environment of sedimentation in the Ghazij Basin. It is concluded that the sediments were formed in marine and fluviatile environments. The principal source area lay to the north-west of Harnai and a palaeogeographic reconstruction of Ghazij times is attempted.

Evidence for the growth of andalusite and staurolite porphyroblasts prior to the first penetrative movements in the rocks of the Mt. Lofty Ranges is presented. The implications of this unusual observation are discussed.

A revised interpretation of the sequence of marine invertebrate faunas from the Svalbard Triassic is given. Correlations are made with the unusually complete sequence now recognized in Canada. The position of the faunas is given in terms of the recently proposed lithostratigraphic scheme. In the Lower Triassic, Griesbachian, Dienerian, Smithian and Spathian faunas are represented; in the Middle, Anisian and Ladinian. In the Upper Triassic only a small part of the Karnian is represented by a marine fauna. No new faunas are recorded but for the first time three ammonoid zones are discriminated within the Anisian.

The type specimen, other figured specimens and supplementary material of Monograptus tenuis (Portlock, 1843) have revealed the presence of pronounced ventral apertural processes which place this species in a unique position in the Monograptina. The affinities of M. tenuis are discussed.

The earliest monograptids are shown to appear at exactly the same time (base of the vesiculosus Zone in Scotland) as Dimorphograptus and Rhaphidograptus, and the earliest species of these two genera are those with long uniserial portions, the forms wiht shorter uniserial portions appearing in the overlying cyphus Zone. Akidograptus is entirely restricted to the premonograptid beds. One of the earliest monograptids is described as Monograptus cyphus var. praematurus var. nov., which has a distinct and earlier range than M. cyphus s.s. Lapworth.

Some thin basaltic intrusive sheets in south-eastern Iceland consist in cross-section of a porphyritic central zone sharply bounded by non-porphyritic margins. Within the porphyritic zone phenocrysts of plagioclase, augite and olivine are arranged in two main layers, an upper layer containing mostly plagioclase phenocrysts, and a lower layer containing concentrations of augite and olivine phenocrysts. The phenocrysts are considered to have been gravitationally sorted during the passage through the sheets of a highly fluid and strongly flowing porphyritic basalt magma.

Volcanic lapelli, bomb-like fragments and dust, along with other ejectamenta were incorporated in the limestone during its sedimentation. The limestone belongs to the Chail Series of Algonkian age. The volcanic explosion took place under sub-marine conditions.

Examples of semi-horizontal mineral layering in adamellites from the Galway Granite Batholith of Co. Galway, Eire, are described and illustrated. The layering results from variation in the amounts of the constituent minerals in successive horizons of the granite. It is suggested that the layering originated by settling of the early crystallizing minerals during quiescent periods in the emplacement of the granite, and that it may have been much more extensively developed than it is at present. Volatile constituents are thought to have reduced the viscosity of the magma periodically.

Chemical analysis of twenty-six amphibolite facies gneisses from western Connemara are treated statistically, and used in conjunction with petrographic evidence to elucidate their origins. It is shown that the gneisses are of igneous ancestry, and have been invaded by material of silica-soda potash composition. The conditions of temperature and pressure prevailing at different times is related to the evolved mineral assemblages, and the whole sequence fitted into the general pattern of events in Connemara.

A likely example of biochemical evolution in the nautiloids is demonstrated, based on X-ray fluorescence analysis of the Sr content of unaltered shells.

Cruziana semiplicata (Salter) is recorded, generally in abundance, from previously known and new localities within Upper Cambrian (Ffestiniog) sediments in Snowdonia, and the Portmadoc area, North Wales. C. furcifera (D'Orb) is recorded for the first time in the British Isles from four localities within Lower Ordovician (Arenig) sediments on St. Tudwal's Peninsula, North Wales.

It is shown that each of these species is of limited but different range, and it is suggested that they could be useful in distinguishing between otherwise unfossiliferous Cambrian and Ordovician strata.

Gravity readings were taken on a 40-km traverse running roughly NE-SW across the Liruei Younger Granite ring complex of Nigeria. A negative Bouguer gravity anomaly of about 16 milligals amplitude was observed over the complex.

Electronic computing methods were used in the interpretation to obtain the best 2-dimensional and 3-dimensional structures which would fit the observed anomaly. The best computed models indicate that the contacts between the Liruei Complex and the surrounding Basement Complex dip outwards from the ring complex and, based on the surface density contrast of 0·10 gm/cc, the depth to the base of the density contrast is of the order of 7,500 metres.

A description is given of potassium feldspar which was produced during the fibrolitization of biotite.

An account is given of the karst features of a given area, and ways of finding some order in their apparently chaotic arrangement. The simplest characteristic to study is the alignments of the karst features. These can be determined either subjectively (following the simple overall impression given by the area), or objectively (on the basis of various mathematical or graphical operations).

A distinction between “local” and “general” alignment by an elementary statistical-graphical method is proposed. This method is applied to the Lake Constance area, and the results are interpretated in relation to the geological features of the area. It is concluded that (a) the structural features of an area have a strong influence on the karst phenomena, and (b) there is a possibility of revealing, and even making geometrical determinations of, some geologically fundamental directions, e.g. tectonic—from an analysis of the distribution of such relatively superficial phenomena as karst features.

The thecal form of Monograptus argutus Lapworth and M. leptotheca Lapworth is similar to that of M. incommodus Törnquist, the type species of Pribylograptus Obut & Sobolevskaya; their thecae are geniculate and have introverted and laterally expanded apertures, and M. leptotheca has in addition apertural hoods. The relationships of these species are discussed.

Tracks believed to have been made by a crawling gasteropod are described from a loose block of Upper Carboniferous grit from Soyland Moor, near Todmorden, Yorkshire.

Calcarea and Hexactinellida are now characteristic of different depth zones, and have shown comparable bathymetric zonation since the Carboniferous period. This paper reviews and discusses relevant evidence from modern and fossil sponge faunas, together with some problems involved in the use of the modern data for the assessment of past depths. The most important independent evidence is provided by calcareous algae and herma-typic Scleractinia.