The unique specimen of Coccosteus angustus Traquair, from the Lower Devonian Hunsrückschiefer of Germany, is redescribed and referred to Gemuendenaspis n.gen. Previously unrecorded details of its morphology and a reconstruction are given. Its possession of both arctolepid and brachythoracic characters is confirmed and it is suggested that Gemuendenaspis should be referred to the family Gemuendenaspidæ nov., which closely approaches what would be expected in ancestors of the Coccosteidæ.

Three new genera and seventeen new species of trilobites from the Flags with Valcourea confinis (Salter) of the Girvan District are described and named, and thirty-six species are figured. The genera constitute a normal Middle Ordovician assemblage for the Girvan District; none of the species is known elsewhere. There is a close resemblance to the fauna of the Lower Edinburg Formation of the Appalachian Valley of the U.S.A., and many of the generic stocks are known earlier only from the Chazy and Lincolnshire Formations of North America.

Excavations in 1958 for the construction of a dam at Loch Droma, Ross and Cromarty, revealed a deep and extensive section in peat and Late-glacial silts. The section was surveyed, its environs studied, and samples of materials analyzed by the Macaulay Institute, Aberdeen, and the Sub-department of Quaternary Research, University of Cambridge. The watershed location of the site, the early radio-carbon date obtained for the basal silts (12,810 ± 155 B.P.), and the nature of their organic contents, make this a critical site for the elucidation of the deglaciation and vegetational history of the Atlantic seaboard of North-west Scotland. In Part I of this report, W. Kirk describes the site and its setting, and indicates some of the problems it raises for existing glacial chronologies of Northern Scotland, and in Part II, H. Godwin summarizes and comments upon the analyses of organic remains.

Garnetiferous peridotite masses which occur among gneisses in the Tafjord district of Norway are cold intrusions emplaced as crystalline rocks late in the metamorphic history of the region. No relationship other than similarity of mineral facies can be established between the peridotites and the eclogite bodies in the surrounding gneiss. Chemical analyses of twelve olivines, fourteen orthopyroxenes, nine chrome diopsides, nine garnets, three amphiboles and two rocks are presented, representing material from the Tafjord and Almklovdalen districts of Norway, a garnetiferous peridotite mass near Bellinzona, Switzerland, and the garnet-peridotite inclusions in the kimberlite pipes of South Africa. Optical and X-ray data for the analyzed and some unanalyzed assemblages are also presented. The mineral assemblages of these rocks are compared with each other, and with data from the peridotites of layered tholeiitic intrusions, alpine-type peridotites and the peridotite nodules in basalts. The garnet-peridotites of Norway, Switzerland and South Africa are believed to be little altered fragments of the mantle, whereas the peridotite nodules in basalts and the alpine-type peridotites are believed to be of igneous origin. Examination of the distribution of cations between the coexisting phases suggests that there are too many variables to permit a reliable interpretation of the results.

The orthopyroxenes from the garnetiferous peridotites are not rich in A1203, contrary to expectations based upon recent experimental work.

The main deformation of the Carboniferous sediments of north-east Northumberland took place in Armorican times. An analysis of minor structures shows that they occur in three distinct structural environments. These are, (i) as accommodation structures to large folds, (ii) as structures produced by transcurrent movement along lateral shearfaults, and (iii) as minor structures formed in direct response to the regional compression. The detailed interrelation-ships of these minor structures are described for selected areas.

In the neighbourhood of Berwick-on-Tweed a major east-facing monocline has been recognized. It appears that the large-scale folding of the Carboniferous strata was directly controlled by the configuration of the Lower Palæozoic and Lower Old Red Sandstone basement. Major folds have been generated by an east-west compression and are deflected around the Cheviot and Southern Upland masses. A regional fault pattern is interpreted as a conjugate system of strike-slip and oblique-slip shears. The nature and influence of structural control on the emplacement of the Whin Sill suggests that it was intruded during this same tectonic episode.

We undertake a re-interpretation of eighteen sheets of the 1: 100,000 Geological Survey map of Italy. Developing the tectonic discoveries of G. Steinmann and S. Lencewicz we group the pre-Middle Miocene rocks of the district in four structural units beginning with the lowest as follows: (1) The rocks seen through the Carrara Window; (2) Spezia Nappe; (3) Liguria Nappe; (4) Genoa Nappe. Our account mainly concerns the Liguria Nappe. In it we find too much layering to admit of G. I. Migliorini's invocation of successive piecemeal landslips. We also cannot agree with certain important features of R. Staub's synthesis of Mediterranean tectonics.

Structures in and around volcanic necks at Dunbar are interpreted as belonging to two different stages in volcanism. Some, which are related to an early neck emplacement stage, include small ring structures—probably incipient (crypto-volcanic) necks—filled with marginally flow-banded breccias, dykes of similarly margined unbedded tuff, and tuff-penetrated wall rocks. Among the last are sandstones veined along planes of minor fracture by very fine sand.

Other structures belong to a later stage during which bedded tuffs, that had originally accumulated sub-ærially, subsided into the necks in a process here likened to caldera formation. In one large neck the bedding is relatively undisturbed, but in smaller necks there are high inward dips from the margins and collapse structures, sometimes accompanied by reconstitution of the clastics, at the centres. Diagnostic features of subsidence margins are anastomozing veins of carbonate, locally accompanied by hæmatite, and these appear to be related to dykes of flow-banded sandstone and sandy tuff intruded along fractures initiated inside the necks during subsidence. Other structures described are ring-fracture, with or without gouge, and down-drag of wall-rocks: these suggest a solution to the space problem posed by caldera mechanism.

Lyginorachis papilio Kidston is shown to possess separate vascular bundles at its base like the leaf-trace in Pitys dayi Gordon. Vascular traces arise higher up indicating that the petiole bore one or two pairs of sub-opposite pinnæ (or pinnules). Above these the primary rachis dichotomizes into secondary rachides with traces to alternate pinnæ. One specimen is known showing the origin of an axis of Tristichia ovensi in the dichotomy.

L. papilio is considered to be a petiole of Pitys and T. ovensi the fertile region of the frond bearing Stamnostoma cupules.

A Histological investigation has been made of growth and repair of periostracum in Mytilus edulis. Physical rather than chemical differences in the processes of secretion can account for the variations in the structure of periostracum which appear during normal growth and in that which follows damage. Amœbocytes take part in the production of periostracum by supplying material for the secretory cells. Reasons for the presence of other granular cells near the site of secretion are also suggested. The periostracum is secreted solely by the epithelium of the inner surface of the outer mantle fold, although initially it adheres to the epithelium of a process of the middle fold. Consideration of the nature of the connection of the periostracum with its retractor muscles leads to the hypothesis that the cells of both epithelia move with the periostracum towards the mantle edge. The tissue where the two epithelia meet appears to be meristematic.

A Small picrite sill of critical significance is examined in detail, from top to bottom, with particular reference to the distribution and crystallization of the olivine. Statistical evaluation of the sizes of olivine crystals establishes a gradation from large phenocrysts to small groundmass crystals. The micrometric data indicate that, while the feldspar content has remained constant, there is an inverse relationship between the distribution of olivine and pyroxene. This relationship, viewed in conjunction with the common tendency toward skeletal crystallization of the olivine and its gradation in size, amounts to substantial evidence that much of the olivine rapidly crystallized at the time when the sill was emplaced. At a few places, the sandstones and grits, into which the sill has been intruded, have been fused. Where it has penetrated a dolerite dyke along its direction of strike, a non-porphyritic facies, with very much less olivine, is associated with xenoliths of peridotite and of fused sandstone. It is inferred, from the field relationships, that this non-porphyritic facies was intruded as a liquid, containing xenoliths, in advance of the picrite. The chemical composition of this liquid is more calcic than basalt. It is concluded that this earlier calcic liquid was followed by a later magnesian (picritic) liquid and that these liquids have probably a deep-seated genetic relationship with feldspathic peridotite. Further research must be directed toward investigating this relationship both experimentally and in picrite—peridotite rock associations.

In Strathaird, Tertiary lavas occupy an area of about 7 square miles and are up to 1000 ft. thick. Most of the sequence consists of alkaline olivine basalts but there is also a flow of trachybasalt and a thin group of picritic lavas. Pyroclastic rocks are rare.

The area lies along the south-eastern margin of the Cuillin gabbro and thermal metamorphism is evident to a varying degree over the whole of the lava outcrop. In the immediate vicinity of the gabbro the lavas have been recrystallized to pyroxene-bearing hornfelses, and these rocks are followed outwards by a broader zone characterized by the presence of actinolite, chlorite, albite and epidote. In the outermost of the three zones, which extends for at least 3 miles from the gabbro, thermal effects are limited to the local growth of chlorite, albite and epidote. When compared with Turner's (1958) scheme of metamorphic facies the inner zone is equivalent to the pyroxene hornfels and sanidinite facies whereas the two outer zones form subdivisions of the albite-epidote hornfels facies. The hornblende hornfels facies appears to be only poorly represented by a few hornfelses found on the outer boundary of the inner zone.

The metamorphism was not progressive since the mineral assemblages of each zone developed independently from unmodified lavas. There is evidence that a small amount of silica was added to some of the inner zone lavas during metamorphism.

Eight new chemical analyses of metamorphosed basalts are presented, together with one new analysis of a metamorphosed bole.

The petrology of a group of geosynclinal rudites and arenites of Upper Ordovician age from the Rhinns of Galloway, south-west Scotland, is described. The rudites are confined to the oldest formation, the Corsewall Group, and consist of pebbly microbreccias and “boulder-beds” interbedded with coarse greywackes and platy siltstones. The composition of the microbreccias and boulder-beds varies little with stratigraphic level.

The arenites comprise lithic, coarse-grained greywackes with occasional quartzose or feldspathic varieties. They carry, in aggregate, a wide range of igneous, metamorphic and sedimentary rock-fragments, quartz of variable source, a variety of feldspars, ferromagnesian minerals, micas, chlorites and a common to conspicuous argillaceous matrix. The greywackes are well defined stratigraphically as regards both overall composition and the character of the large mineral grains and rock-fragments (“granules”). Moreover composition appears to be related to grain-size in a consistent manner. The size-distribution, sorting and skewness of the greywackes based on thin section measurements show little stratigraphic variation.

The aggregate suite of heavy minerals is meagre and only minor differences exist in the individual formation-suites.

The character of the rock-fragments and mineral grains suggests that the earlier formations were derived from a nearby source-area in which plutonic and hypabyssal acid and basic igneous rocks were extensively exposed, together with spilitic lavas and glaucophane schists. The petrology of the upper formations reveals that a metamorphic terrain of Southern Highlands aspect became an important additional source of material. However, the highest beds were derived from a region dominated by andesitic and spilitic tuffs and lavas.

The principal directional sedimentary structures are described briefly and it is suggested that the lower part of the Corsewall Group, derived mainly from the north and north-east, was deposited in a sheltered pro-delta environment, but that the boulder-beds and associated rocks were formed within a more boisterous region. The Kirkcolm Group is a turbidite-sequence deposited in a marine trough of moderate depth by currents which at first flowed dominantly in opposing directions, towards either north-east or south-west. However, transport from the north-east became progressively established. The Portpatrick Group is another turbidite-sequence but this formation was deposited by currents flowing from the west or south-west.

A Stem of Stenomyelon tuedianum Kidston is described with the base of a petiole of Kalymma tuediana Calder attached to it.

Two new species of Stenomyelon are described—Stenomyelon heterangioides, characterized by interspersed xylem parenchyma and mesarch protoxylem, and Stenomyelon primaevum distinguished by a solid tri-radiate protostele lacking parenchyma bands. The possible external features of Stenomyelon are compared with a compression of a Pteridosperm with large fronds.

Incomplete, but structurally preserved remains of an organism referable to the Nematophytales Lang, are described from the Rhynie Chert as a new genus and species. The fossil is composed of a plexus of non-septate tubular cells of two types—the smaller having uniformly smooth walls, the larger, walls with conspicuous spiral thickenings. Branching of both types is localized in areas referred to as branch-knots. Comparison is made with other members of the Nematophytales which have been shown to possess differentially thickened tubes.

Outstanding structural features related to habits of life in the chydorid cladoceran Eurycercus lamellatus are described. Crawling is as important as swimming in this deposit-feeding species. The nature of the food, its collection and subsequent manipulation, are described. Both cephalic and trunk appendages are involved in this process. Their structure and mode of action are described and illustrated in detail. Many hitherto unknown structural features are described and the functional significance of these and other morphological peculiarities is explained.

Material of a coccosteid fish, from various localities in Caithness, is described as Dickosteus threiplandi n.g., n.sp. The fish has previously been confused with Coccosteus cuspidatus Miller ex Ag. ( = Coccosteus decipiens Ag.). A diagnosis of this new form is given and comparisons made with Coccosteus show that it is quite distinct. Coccosteus fletti Watson is also redescribed and referred to the new genus Watsonosteus. The phylogenetic relations and stratigraphical distribution of these two genera are considered, and it is shown that Dickosteus occurs in Caithness in the Thurso Flagstone Group above the Achanarras horizon, apparently replacing Coccosteus, and has a similar range in Orkney. Watsonosteus is characteristic of the Eday Flags. The stratigraphy of the Thurso Flagstone Group is critically reviewed and compared with the Orkney succession; the Ackergill Beds are shown to be the probable lateral equivalents of the Mey Beds, and the consequences of this are examined.

The paper is concerned with one of the marginal parts of the Laxfordian complex of the Lewisian of north-western Scotland where the older Scourian complex (c. 2500 million years) was reactivated during the Laxfordian orogeny (c. 1600 million years). The effects of Laxfordian deformation are discussed with reference to the distortion of Scourian structures and post-Scourian dolerite dykes and to the orientation of newly-developed structures. The arrangement of structures N.E. of the Laxfordian metamorphic front is thought to result from rotation of pre-existing planar elements during compression on north-east-south-west lines, without the development of very large folds. The connection between the style and arrangement of Laxfordian structures and the metamorphic state of the rocks at the time of deformation is illustrated with reference to both local and regional variations, and some implications of the regional changes in the structural pattern are discussed.

The arctolepid fish “Phlyctœnaspis” germanica is redescribed as Stuertzaspis n.gen. An interpretation of the head shield is attempted and it is suggested on this evidence that the fish is a relatively unspecialized member of Denison's subfamily Actinolepinæ. On the ventral surface of the fossil is preserved the postethmo-occipital ossification of the neural endocranium, a structure previously satisfactorily known only in Kujdanowiaspis among the Arctolepida. Generally the endocranium of Stuertzaspis is similar to that of Kujdanowiaspis, although it shows some interesting differences, particularly in the orbital and occipital regions.