A Large number of structurally preserved lycopsid axes from the Lower Carboniferous of Scotland are described and designated as a new genus and species. A comparison of this genus with other lycopsids is followed by a discussion of the development of the secondary cortex, and several other interesting structural features.

The results are presented of a detailed petrological reconnaissance of a group of picritic minor intrusions in the Hebrides. A substantial amount of new factual data is subjected to a unified treatment as a basis for reference and discussion. Olivine phenocrysts are not appreciably zoned and there is no evidence that they have a reaction relation with the liquid represented by the groundmass. Variations in the size and amount of olivine in individual intrusions are examined in detail and attributed to composite intrusion of differentiated material. A distinctive non-porphyritic facies found in several sills and in one dyke is chemically analyzed. Four analyses from widely separated localities establish this facies as a remarkably invariant, eucritic rock-type. The composition of the groundmass of the picritic rocks is variable and there is no evidence whatever of the participation of basaltic magma in their formation. Although no attempt is made to explain the new data in detail, a comprehensive working hypothesis is formulated. The origin of such picritic intrusions is believed to be due to selective fusion of pre-existing ultrabasic rock. Liquid more basic than normal basalt magmas can be formed by this process. Some re-precipitation of olivine may have preceded final emplacement of a magnesia-rich liquid which contained xenocrysts, mainly of olivine, from the source rock.

The life history of Petrobius brevistylis Carpenter is described from material reared in the laboratory and captured in the field (south Devonshire). A method of identifying the first eight instars is discussed and their diagnostic morphological characters described. Fecundity and time of oviposition are considered at some length. The effects of climate on various phases of the life history are considered as well as the faunas found associated with P. brevistylis. A brief description of the life history of P. maritimus (Leach) is included.

The scent-producing area of closely packed holocrine and apocrine skin-glands in Aotes has an atypical, caudal position. Whilst most of the holocrine glands open into hair follicles by ordinary short ducts, some of the ducts are elongated, opening either into follicles or on the skin surface. The holocrine and apocrine secretions, in conjunction with the peculiar splitting of individual hairs, cause felting of the pelage on the gland field. A peculiar structure of the hairs facilitates their splitting. Evolution and function of the gland field are discussed.

This study of the mineralogy and metamorphism of the Moine schists approaches the problem through consideration of the chemical composition of the minerals. The principal minerals of the Moine schists are studied individually, thirty-three new analyses of minerals being given, with four of schists. For all but six analyses the trace elements have been determined and are tabulated. Muscovites, biotites and garnets all show variation of composition with increasing metamorphic grade, respectively with decreasing Fe2O3 and SiO2, increasing MgO and Al2O3, and decreasing CaO plus increasing MgO, these being only the principal variations. The crystal chemistry of the muscovites, biotites and garnets is briefly discussed. Some new data are presented for the relationship of plagioclase and epidote, a relationship which can only be used with extreme caution to indicate metamorphic grade. A dependence of the incidence of a sutured quartz aggregate in psammitic schists upon the microcline content is noted, and it is suggested that the incidence of the breakdown of quartz under the combined effect of temperature (the dominant cause), stress and potassio solutions, all active in the core, is responsible for the production of the core-envelope boundary. This boundary transgresses the strike; within it retrogressive changes have converted Garnet-zone schists to Biotite-zone schists, but outside it the only retrogressive change is garnet to chlorite. The retrogressive metamorphism formed a distinct episode separated from the initial regional metamorphism by an unknown time-interval; during the second metamorphism isotherms were concentric with the dome, declining outwards. The evidence of an epidiorite from the west coast of Morar suggests that during the first metamorphism the zonal state there was that of the Dalradian Biotite-zone; “almandine” garnets in the adjacent schists are extremely rich in CaO and are in equilibrium with microcline.

An attempt has been made to determine the identity of two desmids commonly recorded from the plankton of British lakes, Staurastrum paradoxum and S. gracile. The original descriptions of these species were clearly inadequate and many subsequent investigators have given their own interpretation as to their identity, so that from the British plankton alone at least six well-defined taxa have been referred to as S. paradoxum and four as S. gracile. Owing to this confusion, and in the absence of type material, it is suggested that the species S. paradoxum cannot be maintained. On the other hand, type material of S. gracile exists in the British Museum and has been re-examined. The principal characters of this species are described and figured and a list of synonyms given. In addition, those Staurastrum species and varieties frequently misnamed paradoxum or gracile, have been described in detail.

An analysis of the structural style of the Palæozoic rocks exposed around Girvan in S.W. Ayrshire suggests that it was fashioned by at least nine phases of deformation. Five of these phases were active when maximum pressures were horizontal and together constitute the local expression of the Caledonian orogeny. The oldest phase recognized, the Main fold phase, consisted of overfolding due to an over-riding maximum pressure from between 150° and 170° and was penecontemporaneous with thrusting generated by a modal maximum stress from 145° to 325°. Three important thrust belts resulted but there were considerable local swings in the azimuths of maximum stress, a variation which culminated in the propagation of the Ardwell fold and reverse fault phase by a maximum stress from 110°. Later Caledonian movements, presumably influenced by an increase in overburden due to folding and thrusting, were represented by two episodes of wrench faulting: an older Ardwell “cross-fold” phase due to a maximum stress from north-east to south-west and a younger Main wrench system with a maximum stress aligned at 160–340° which generated an intricate pattern of sinistral and dextral shears together with second-order relatives. The three following phases, the first, second and third “normal” phases represented an episode in stress history when the relief of pressure was horizontal and aligned from approximately north to south, north-north-west to south-south-east and just north of west to south of east respectively. Maximum pressures tended to vacillate between the vertical and near horizontal and as a result much of the faulting was oblique-slip. All three phases were responsible for important faults and some evidence is put forward to suggest that all three are possibly Proto-Armorican or probably not later than Armorican, although the existence of a few mineral veins shows that reactivation certainly took place in Borcovician times. An analysis of the tensional joints recorded for the area indicates that, apart from the dominant Caledonian and less conspicuous Armorican sets, Tertiary joints were formed when there was a relief of pressure from north-east to south-west and this final phase of deformation was accompanied by the intrusion of dykes.

The study also includes discussions on the methods and merits of the resolution by stereographic means of the stress fields responsible for oblique-slip faults and on the nature and origin of first- and second-order wrench faulting in the light of the abundant statistical data available.