A trilobite fauna of Llandovery/Wenlock age is described. Five species are represented:Rhax polllnctrix gen. et sp. nov. (Scutelluidae), a warburgelline?, Sphaerexochus sp.,Encrinurus? sp., and a calymenid. The morphology of R. pollinctrix supports the view that Bumastus is a scutelluid, and consequently that the Illaenidae, as presently conceived, is polyphyletic.

Small-scale igneous layering and lamination have been found in the gabbro of the Eastern Lizard, Cornwall. An origin by gravitational settling of plagioclase and olivine crystals is proposed. Several post accumulation factors have obscured the lateral continuity of these features.Their present orientation suggests that the gabbro has been rotated through approximately 90° about an E—W axis and‘ tops’ to the N. This invalidates the idea of an in-situ ring intrusion but is in keeping with the ophiolite model for the Eastern Lizard.

The palaeoecologic significance of post-Palaeozoic green calcareous algae is evaluated with what is known of the environments of comparable living algae. Here requirements and tolerances of temperature, bottomsediment, salinity and water-energy may be observed; depth is apparently significant only as it influences these. In the extinct algae, only a minority show clear taxonomic relationship to living algae, in palaeo-environmentsdeduced from independent evidence. Codiaceae and Dasycladales seem to have had environmental preferences like their living descendants, with preferredmicroenvironments in some genera.

The Adrano area covers approximately 150 km2 of the tower SW flanks of Mount Etna, Sicily. A wide selection of the rocks that occur on the volcano are represented in the area. Lavas of alkalic affinity form by far the greater proportion of the volcanics in the area, and comprise a trachybasaltic suite of lavas ranging from hawaiite through mugearite to benmoreite. There appears to be no overall progressive variation in the chemistry of these trachybasaltic lavas with time; rather that the parental magma has remained fairly constant in composition. Periodically, however, this parental magma has been able to differentiate into more evolved products. The chemical variation shown by the trachybasaltic lavas can be largely explained by crystal fractionation of augite, olivine, plagioclase and titanomagnetite at moderate to low pressures. Crystal fractionation, however, cannot explain the variation in the alkalis which is thought to be affected by volatile transfer.

Calcirudites in the Upper Devonian (Frasnian) of Central Poland are often couplets with a laminated intrapelsparite upper part and a lower section of intraformational calcarenitic and micritic flat pebbles. The pebbles are associated with bioclasts derived from 3 offshore environments: I, a fully marine area (echinoderms, rugose and tabulate corals, brachiopods, trilobites and conodonts); II, phytogenic banks (globose stromatoporoid stromatolites and Renalcis); III, restricted lagoons (ramose stromatoporoids, calcispheres, ostracodes and peloids). Many of the flat pebbles are only slightly displaced and had been partially cemented before being reworked. The depositional environment was subtidal. The considerable size of the flat pebbles and the complex nature of the surrounding matrix suggest that storm surges or tsunami may have disrupted beds and led to channelling and pebble formation.

The Glen Park Member of the Sulphur Springs Formation (Devonian) in east-central Missouri contains abundant phosphate nodules. Dissolution of several nodules in hydrochloric acid yielded a diverse, well-preserved Ordovician fauna, containing diagnostic graptolites, ostracodes and conodonts, demonstrating that the Glen Park phosphate nodules are reworked from the Ordovician. Faunal similarities and the in situ occurrence of phosphorite in nearby exposures of the Mequoketa Shale (Ordovician ) strongly suggest hat phosphate nodules in the Glen Park were reworked from the Maquoketa.

In 1957, Hudson, Eames & Wilkins proposed the name of Hammar Formation for a series of sands and silts below the surface alluvium of the Mesopotamian Plains near Basrah, Iraq, which yielded a marine molluscan fauna of Holocene age. This paper shows that deposits yielding a very similar molluscan fauna are present at shallow depths at Amarah and Qurmat Ali, and lists the numerous foraminifera recovered from these deposits. Marine or brackish water conditions are thus shown to have prevailed in recent times over a distance of at least 250 km NW of the present head of the Persian Gulf.

A modified fission track technique has been used for datingbiotite flakes from crystalline rocks of Khammam district in Andhra Pradesh, India. The recorded fission track ages of 368±15 Ma to 616±20 Ma, with a mean of 475±90 Ma, correspond to the period of the Indian Ocean cycle. The data suggest an average cooling rate of about 0.6 °C per million years for the closing phase of this cycle.

An unusual type of mottled area is described from titaniferous augites in the Dippin sill, Isle of Arran. These are characterized by abundant magnetite inclusions, irregular embayed outlines and distinctive chemical compositions. The possibility that these are due to zoning, especially sector zoning, is examined and discarded. They probably represent partly resorbed relics of pyroxene which crystallized at depth prior to the emplacement of the sill. As such they could have considerable petrogenetic implications both with regard to the sill itself and to alkaline basic magmas in general.

The Late Precambrian and Early Cambrian strata in eastern California and Nevada can be divided into 3 facies – the eastern Craton, the White-Inyo, and the Death Valley. These 3 facies supply evidence of 3 trilobite zones – the Fallotaspis, the Nevadella and the Bonnia-Olenellus; the inter-relationships are outlined. Correlations with the Siberian Platform successions are discussed and the Precambrian–Cambrian boundary is tentatively placed within the beds of the upper Reed Dolomite in the White-lnyo Range.

A new total degassing argon-40/argon-39 age determination is given for crystals of fresh adularia from hydrothermal veins within the amphibolites near Porthkerris Point, the Lizard, Cornwall. The apparent age of 211±2 Ma obtained is regarded as a close minimum age for crystallization of the adularia. There appears to have been only one phase of crystallization of primary hydrothermal adularia, about 210–220 Ma, in the granulites and amphibolites in the vicinity of Porthkerris Point and in the gabbro of Dean quarry. Another hydrothermal event occurred c. 160–170 Ma. Younger apparent ages have been attributed to hydrothermal activity at one or more subsequent periods.

There are close geometrical and dimensional similarities between the faults in Scotland north of the Highland Boundary Fault and faults in southern California east of the San Andreas Fault. It is argued that the Moine Thrust and Oarlock Fault are equivalents and that the Great Glen Fault and the Rosamund Lineament are also equivalent, implying corresponding senses of movement and that the Highland Boundary Fault originated as a dextral transform. The comparison cannot be extended yet to the terrains to the N of the Oarlock Fault or W of the San Andreas or to the corresponding areas in the Caledonides.

Two regions are considered to be the best for the definition of the Cambrian lower boundary in Siberia – in Yakutia (the middle course of the Aldan River), in Western Prianabarye (at the Kotuikan and Kotui). The stratigraphical relationships in these 2 regions are described. Some general problems of stratigraphy are then raised (a) the need to use lithologic-facies, palaeogeography and biostratigraphy together, (b) the boundary stratotype method of delimiting chronostratigraphical subdivisions and (c) the earliest trilobite zones, the Ediacara fauna and geochronology.

Richardson's (1911) detailed correlations of the Upper Rhaetic and Lower Lias strata of W Somerset are in need of revision; he wrongly identified the basal Langport Bed as the Cotham Marble at Blue Anchor and Lilstock. Likewise, his correlations of the Upper Rhaetic and Lower Lias strata between W Somerset and Glamorgan are erroneous; the lower parts of his Glamorgan Langport Beds were equated with the upper part of his W Somerset Cotham Beds. The greater part of the W Somerset Watchet Beds are, in the hand specimen, lithologically similar to Liassic shales and not to the White Lias ‘marly’ beds of Lavernock as he stated. The matter is important because the W Somerset coast is the recommended type area for the base of the Jurassic System, and Richardson&s classification of the strata is taken as the starting point for fixing this horizon.

The orthidine brachiopod Heterorthis alternata (J. de C. Sowerby 1839) is here recorded from the River Onny Cliff Section at an horizon high in the Onnia superba Zone of the Onnian Stage. Previously it had only been recorded from rocks of Upper Longvillian, Marshbrookian and Actonian age of South Salop and of Upper Caradoc age of Morocco.

A previously undescribed series of outcrops which lies nearBishop's Castle, 3.2 km S of the Longmynd-Shelve Area of Salop (Shropshire), displays a relationship between the Western Uriconian tuffs, WentnorSeries ashy turbidites (both Pre-Cambrian) and Ludlow Series siltstones. This throws further light on the structure of the Pontesford-Linley Disturbance, indicating that, in the vicinity of the outcrops, a component of its movement may have been post Ludlow in age.

Two small outcrops of harzburgite and asbestos-bearing serpentinite, occurring S of Di Zahav in eastern Sinai are the first record of ultramafic rocks from the Sinai Precambrian massif.

The zonal pattern of metamorphism in the Scottish Highlandsis more complex than that suggested by Chinner. It has been disrupted by major tectonic dislocations and cannot be interpreted as a simple thermal anticline. Retrogression and inversion of zones seen in NW Scotland may resulteither from structural perturbation or the interference effects of superimposed metamorphism. A sinistral displacement of the Great Glen Fault still seems to match the metamorphic patterns in the opposing blocks, even if allowance is made for a major downthrow to the SE.

The discovery of Ediacara type faunas and later the Tommotian fauna at levels below the supposed first appearance of trilobites has brought new life to the discussion of the formal position of the Precambrian–Cambrian boundary. The oldest shelly faunas are apparently restricted to a few favoured areas, whereas transition beds developed as quartz sandstones, mostly unfossiliferous apart from trace fossils, seem to have a much larger regional distribution. The sequences of quartz sandstones overlie a Precambrian crystalline basement of a much greater age or clastic sediments, in part tillites, and are in turn overlain by a variety of rocks containing olenellacean trilobites.

The lowering to the Cambrian boundary makes the correlation of the widespread marine sandstones below levesl with trilobites highly pertinent. The correlation of some such sandstones in Greenland and Scandinivia is discussed below. In this account the Tommotial Stage is regarded as the basal Cambrian stage.