Detached petioles and their branches are described under the name Lyginorachis arberi sp. nov. In their anatomy they resemble the petioles of Rhetinangium arberi Gordon, a presumed Pteridosperm. Two specimens show preparation for dichotomy. Others are interpreted as rachides probably formed by dichotomy of petioles. In cross section such rachides show the presence of pinna-traces arising alternately and marginally from the V-shaped vascular bundle. The pinna bundles are also V-shaped but have only three corrugations in section. Cylindrical pinnules are borne on the pinnæ.

L. kidstoni sp. nov. is a smaller petiole with a less corrugated and C-shaped vascular bundle. Both species are associated with seeds of Genomosperma.

The structures and mineralogy of the Tertiary ultrabasic and basic intrusions are described. The ultrabasic rocks are thought to be remnants of a layered intrusion which once extended from Hirta to Boreray, and which probably formed by crystal accumulation. The eucrites may represent higher levels of this intrusion. A 350 feet-thick, fine-grained margin is described from the East Glen Bay Gabbro. The metamorphism of the ultrabasic and eucritic rocks, and the formation of the Glacan Mor Complex, probably occurred in a basic environment, before intrusion of the first acid rocks on St. Kilda. Five major-element and twenty-two trace-element analyses are presented.

With the exception of Pterygotus rhenaniœ Jaekel, for which the new genus Jœkelopterus is proposed, the published accounts of the median abdominal appendages of the Pterygotidæ are inadequate. An examination of the British material was undertaken with a view to improving our knowledge of the opercular anatomy of the family. An account is given of the genital appendages associated with both sexes of Erettopterus bilobus (Salter) and Pterygotus anglicus Agassiz, of the Baltic species Erettopterus osiliensis (Schmidt) and of British forms in which only one type of appendage is known. Attention has been given also to the cheliceræ of the British type species because of the importance which has been attached to this character in classification. The significance of the chelate and genital appendages in the classification and biology of the Pterygotidæ is discussed.

Nebria brevicollis (F.) and Philonthus decorus (Grav.) are two of the commonest predaceous insects of the woodland floor, and the head structure, mouthparts and feeding methods of each have been compared and contrasted. In N. brevicollis, the mandibles are well developed for the capture and shearing of the prey, whilst the laciniæ of the maxillæ form rakes which pull the food towards the cibarium across the smooth labium. Food is bolted in large pieces and stored in the crop before passing through the filtering and grinding gizzard. A fundamental difference between the two beetles is seen in the movements and structure of the maxillæ, and a mechanism whereby stipital abduction and protraction is effected in N. brevicollis has been proposed. In P. decorus, the mandibles are also developed for prey capture but hold the prey between large brushes while it is being crushed. The maxillæ form thick brushes which also hold the prey, and the labium-hypopharynx is densely covered with setæ which prevent the entry of solid food into the mouth. Thus, in contrast to N. brevicollis, the labrum has a median food groove which directs the food upwards and away from the mouth, and returns it to the mandibles to be re-chewed. Here, partial external digestion occurs and fluid food is sucked in by the powerful cibarial pump, and passed to the filtering proventriculus. In order to show how the two feeding methods described fit into the general pattern, the feeding methods of various predaceous Coleoptera have been reviewed in relation to different types of gut structure.

The Granophyric Quartz-dolerite is one of a number of intrusions having arcuate outcrops which are concentric with respect to Centre II, Ardnamurchan. It is composed of three rock types: porphyritic dolerite, aphyric dolerite and granophyre. The granophyre extensively net-veins the two kinds of dolerite. However, the development of the net-veining was only the last stage of its intrusive activity. Relationships between granophyre and aphyric dolerite are such as to indicate that at an earlier stage both were in a magmatic state at the same time; that is, they were intruded together, though movement of granophyre magma persisted after the aphyric dolerite had solidified. Evidence is presented to show that intrusion of the porphyritic dolerite was the first episode, and that this provided the host rock for the simultaneous intrusion of aphyric dolerite and granophyre. In its role as host rock, the porphyritic dolerite was at first incompletely crystallized, but for later intrusions it had consolidated. When both dolerites were solid they were net-veined by the granophyre.

The inner contact of the Granophyric Quartz-dolerite was formed by a later intrusion. The outer contact for much of its extent dips fairly gently outwards, and it would seem that where this is so intrusion was more nearly in a horizontal than a vertical sense. Locally, sheeted relationships between the three members of the Granophyric Quartz-dolerite, being gently inclined, support this conclusion. There are several possibilities as to the form the intrusion might have, and these are discussed.

Bouguer anomaly maps covering most of Ayrshire at a density of about one station per sq. km., show a close relationship between anomalies and the distribution of the Upper Palæozoic rocks in the area south of the Inch-gotrick Fault, but are less clearly interpreted to the north, where thick dense igneous masses are present.

In central and south Ayrshire the gravity field may be largely interpreted in terms of the known density-contrasts at the interfaces separating Upper and Lower Old Red Sandstone, and Lower Old Red Sandstone and Lower Palæozoic rocks. The major structure, the Mauchline Basin, is reflected clearly in the largest anomaly, and there is evidence of a culmination of its south-western limb near Kirkoswald. The important N.E.–S.W. faults also give rise to large anomalies, which may be connected with the known geology. It is inferred that they moved as normal faults in Carboniferous times, and that the adjacent synclines are essentially sags associated with the fault displacements. There is geophysical evidence that both the Southern Upland and Kerse Loch Faults existed in Middle O.R.S. (proto-Armorican) times. It is concluded that a hypothesis of N.–S. Armorican stress is not valid in south Ayrshire.

In north Ayrshire, many of the anomalies are best explained by changes of thickness of the Millstone Grit lavas and of the Clyde Plateau lavas, and by the presence of thick dolerite intrusions. Additional evidence is needed, however, before final conclusions may be drawn.

Samples from the various horizons of five soil profiles representative of diverse types widely occurring in north-east Scotland were intensively examined, after separation into particle-size fractions, by appropriate instrumental and chemical techniques including optical examination, X-ray diffraction, electron microscopy and diffraction, infra-red absorption spectroscopy, thermal analysis procedures, chemical analysis and selective chemical dissolution. The results obtained are presented and assessed with respect to quantitative estimation of the mixed SiO2-Al2O3-Fe2O3 gel system occurring in these soils. At best results can be only semiquantitative, but interesting trends are observable in each profile and marked differences are noted between profiles on different parent materials, although this effect is somewhat obscured under impeded drainage conditions. The maturity of the soil is also a significant factor. Results in general can be explained in terms of current concepts on pedogenesis.

Dividing and non-dividing nuclei in the hyphæ of M. androsaceus and M. rotula, grown by means of agar- and cellophane-film techniques, were examined alive with phase contrast and also after various fixation and staining procedures. The division was compared with that of the nuclei found in the ultimate clamp connection, i.e. that found, associated with the developing basidium, and with the divisions of the single diploid nucleus in the mature basidium. The end products of all the hyphal divisions are the same as in organisms having a conventional mitosis but some of the steps by which this is achieved are unusual, notably the arrangement of the chromatin as a figure of eight, the twisting of one of the loops so formed above the other to create two rings and the opening of these rings in such a way that the two rods which, ultimately separate each correspond with the chromosome complement of a daughter nucleus. The first division of the diploid nucleus in the basidium is noteworthy for the linking together, in late prophase, of the four chromosomes. This division is followed by a distinct interphase in which nucleoli reappear. The second division shares the peculiarities of the division in the ultimate clamp.

Results are presented of a cytological survey of the Pteridophyte flora of Jamaica. Approximately 270 species or cytotypes were investigated, only a few of which have previously been investigated from other parts of the world. Several genera have been cytologically examined for the first time and their phylogeny has been discussed in the light of these findings. A number of species complexes and interspecific hybrids have been revealed. The overall statistics of the survey are compared with those compiled from an investigation of the Pteridophyte flora of Ceylon, by Manton and Sledge (1954). Finally, endemic species are discussed in the light of the cytological results and the time known to have been available for their establishment in Jamaica.

In the western Midland Valley of Scotland and the neighbouring areas of the south-western Grampians and Southern Uplands, the regional Bouguer anomalies may be resolved into (i) a westerly-rising component similar to that prevailing throughout western Scotland, and (ii) a broad high over the central zone of the graben with marked decreases towards the bordering mountains.

When allowance is made for the contribution to the gravity anomalies of the light Upper Palæozoic rocks within the graben, the adjusted values outline an accentuated high over the graben with a drop of 25–30 mgal from the maximum to the northern limit of the area and with a corresponding drop to the south. In a profile normal to the major geological structure, the shape of the high approximates to a parabola with its apex 5 miles north-west of the Inchgotrick Fault.

These regional changes may best be explained by a thickening of the Upper Crustal Layer under the Grampians and Southern Uplands, most probably by the addition of thick Lower Palæozoic and Dalradian geosynclinal deposits. Thicknesses of the order of 17,000 ft., additional to those under the Midland Valley, are required to account for the gravity changes. The relative attenuation of the succession in the Midland Valley area, implies that the area of the graben was already a crustal entity in pre-Upper Palæozoic times.

The anomalies accord qualitatively with isostatic compensation of topography. The predominant high positive background values, have, however, no significance peculiar to the graben area.

The holotype and only known specimen of Rhachiosteus pterygiatus Gross is partially redescribed and new restorations are given. Attention is drawn to important points in its osteology and the possible development of a cutaneous sensory system. A definition of the family Rhachiosteidsæ Stensiö is given. This family differs from all other described groups of euarthrodires in the lack of posterior lateral and posterior dorsolateral flank plates. Rhachiosteus is a pachyosteomorph brachythoracid, as defined in the text, and may be fairly closely related in some way to the (coccosteomorph) family Coccosteidsæ. There is no indication that it is closely related to any other known pachyosteomorph, or to other groups of arthrodires, such as the Rhenanida and Ptyctodontida, in which there are no posterior flank plates.

The country lying between the head of Loch Ainort and the northern end of the Blaven Range in central Skye forms part of a Tertiary igneous complex. Country rocks in the area are Jurassic sediments. The earliest igneous rocks are basalt lavas which show the effects of thermal metamorphism by a later intrusion of eucrite and gabbro. This latter, which is part of the Blaven mass, has features of a layered intrusion such as igneous lamination, repetition of layers rich in certain minerals and comparable textures. It may be correlated with zones of the Cuillin layered intrusion. The eucrites are cut by a cone sheet swarm. Adjacent to the eucrite is a vent breccia which contains eucrite blocks, is not cut by cone sheets and is, therefore, of later age than the eucrite. The major part of the area under discussion is formed from four granitic ring dykes and a hybrid suite with ring dyke form, all of which belong to the Western Redhills intrusive complex; in addition, part of a fifth granitic ring dyke, which probably belongs to the Eastern Redhills intrusive complex is included in the area. The granites are mainly fayalite-hedenbergite types with a variety of phenocrysts of felspar and features characteristic of high level intrusions such as granophyric texture and varying optical and chemical properties of the felspar indicating higher temperature modifications. Three new chemical analyses of the granites and one of ferrohedenbergitic pyroxene are presented. The granites may be regarded as partial remelts of the underlying basement gneiss and a simple investigation of thermal requirements indicates that the heat necessary for the partial melting could be provided by a mass of basic rock presumed from geophysical evidence to underlie the complex. Various acid and basic minor intrusions in the area are also described.

The marine invertebrate macro-fossils of the principal marine bands of Namurian age in Central Scotland are described. The species identified are listed and the vertical and lateral distributions of some species within the region are discussed together with notes on the palæogeography and palœoecology. Notes on the morphology of certain species are given and Campylites carbonarius (McCoy), Dyscritella leei sp. nov., Koninckopecten gen. nov. (type species Limatulina scotica Hind), Myalina mitchelli sp. nov., Palœoneilo mansoni sp. nov., Paleyoldia macgregori sp. nov. and Schizodus portlocki (Brown) are described.

Structural features related to habits of life are described for the thermosbænacean Monodella argentarii. Although it can swim, this minute malacostracan is essentially benthic in habits, and its food consists of bottom detritus. The collection and subsequent manipulation of food are described. Monodella is not a filter feeder and no currents are involved in the feeding process which consists essentially of scraping, brushing and pushing. Cephalic appendages only are involved. The structure and mode of action of the mouthparts are described and illustrated in detail, and the functional significance of many structural features is explained.

No justification is found for placing the Thermosbænacea in a separate division, the Pancarida, and its position within the Peracarida is discussed.

The past history and present distribution of the Thermosbænacea are reconsidered.

Detailed mapping and accurate levelling of fluvioglacial and raised marine features in the Forth Valley between Stirling and Burntisland show that the most conspicuous late-glacial raised beaches of this area are associated with the Perth Readvance and possess a marked gradient down the Forth Valley. The relation of the raised beaches to fluvioglacial deposits is described and discussed and this leads to the conclusion that the Perth Readvance resulted in a renewed downwarping of the land, the response to glacial loading and unloading being immediate and rapid.

Lepidodendron calamopsoides sp. nov. is described from petrified protostelic stems formerly considered identical with Levicaulis arranensis Beck. The stems range from 2 to 20 mm. diameter and some possess leaf-cushions usually about 10 × 1 mm.

Three specimens are known showing the transition from stem to rooting organs. Secondary xylem has only been seen in the transition region and rooting organs. The latter resemble Calamopsis dubia Solms-Laubach now considered to be part of the closely related Lepidodendron saalfeldense.

Two new species of petrified seeds Eosperma edromense, and Anasperma burnense gen. et sp. nov. are described from the Cementstone Group of Berwickshire. Anasperma shows that the anatropous condition existed among Palæozoic ovules; it has a single integument with two lateral apical lobes.

Rachides of Stauropteris berwickensis sp. nov. and associated megasporangia are also described.

An account is given of the theory of the telomic origin of the first ovular integument. The second (outer) integument in Angiosperm ovules may therefore have evolved after the establishment of anatropy, either from the first integument or as an overgrowth of the chalaza. Evidence is cited to support the theory that Angiosperm carpels have evolved from dorsiventral bivalved cupules.

Three cupules of Eurystoma angulare are described; they bear one, six, and ten attached ovules respectively. The cupules are built up of several terete branches which dichotomise in successive planes at right angles. Where an ovule is borne a small number of dichotomies are adnate basally so forming an ovuliferous syntelome.