Morphological and physiological features indicate Metriorhynchidae as the only group of crocodylomorphs with a pelagic lifestyle. Some of these features have evolved convergently in several clades of tetrapods secondarily adapted to aquatic life. One striking feature of metriorhynchids as compared to other crocodylomorphs is the morphology of the pelvic region (i.e., ventrally deflected sacral ribs and reduced pelvic girdle), which increases significantly the depth of this region. This morphology, as a whole, resembles that of other viviparous Mesozoic marine reptiles not phylogenetically related to metriorhynchids. We tested two alternative hypotheses of reproductive strategies in this clade: oviparity vs. viviparity. Given the lack of direct evidence supporting one or the other, we explored the use of evidence that may disconfirm either of these hypotheses. Using this counter-inductive approach, we found no cases contradicting viviparity in metriorhynchids, except for their phylogenetic position as archosaurs. A survey of reproductive modes amongst amniotes depicts the evolutionary plasticity of the transition to viviparity, and a widespread occurrence among tetrapods secondarily adapted to a marine life. Assuming oviparity for metriorhynchids implies egg-laying out of the water. However, their postcranial morphology (i.e., features of fore and hind limbs, pelvic girdle, and tail) contradicts this possibility. In this context, we rejected oviparity for metriorhynchids.

The striking morphological similarity that exists between appendages of the extant portunid crabs, such as Callinectes sapidus, and those of the extinet eurypterids has long been noted. The fifth pair of pereiopods in blue crags and other portunids are modified to form the broad, flat, highly mobile ‘swim paddles.’ A nearly identical modification is seen in the sixth pair of prosomal appendages of many eurypterids. The similarities are due to convergence and not to shared descent.

The kinetics of blue crab swimming were studied using high speed films. The animals are capable of slow upwards locomotion (‘hovering’) and rapid sideways swimming. The blue crab paddles apparently act as reciprocating hydrofoils, employing well-understood principles of lift and thrust generation to overcome the animal's weight and drag. Experimental studies indicated that the paddles are capable of producing appreciable amounts of lift. Drag on the body and paddles was also determined. Resxults are similar to those obtained in previous studies of bird and insect flight.

The physical principles employed to study blue crab swimming can be applied to the study of eurypterid locomotion. The eurypterid paddles may have functioned as hydrofoils, producing lift and thrust on forestroke and backstroke. Eurypterids were probably highly agile and manoueverable swimmers, capable of hovering and of high speed swimming. This model predicts observed morphological correlates. Predicted morphological correlates of earlier models (often based on analogies with Limulus) were not found.

The observed convergence between eurypterids and blue crabs may have resulted from similar functional constraints and parallel phylogenetic histories.

Two plants are described from fragmentary remains preserved in the Windyfield chert, situated c. 600 m from the classic Rhynie chert locality. Both are sometimes coated by a microbial film. The larger, fertile axes are placed in the new genus and species Ventarura lyonii. They possess a distinctive, sclerenchymatous middle cortex and terete xylem, and marginally dehiscent, lateral sporangia. The new taxon is similar to the Rhynie zosterophyll Trichopherophyton teuchansii, but is placed in a new genus on sporangial differences. Associated smaller axes with unicellular epidermal outgrowths lack the middle cortex of the larger axes and often have medullated protosteles. They are interpreted as subterranean rhizomes and probably belong to the new fertile taxon, but organic continuity between the two has not been demonstrated.

In a previous paper (4) the quantitative distribution of the molluscs and polychætes in certain intertidal muds and sands on the Scottish Coast was discussed, but there still remained several other types of shore such as (a) a river mud-flat, (b) grounds at the heads of sea lochs on the West Coast, and (c) the more exposed shores of the Western Islands, where conditions might possibly differ greatly from those already considered, with corresponding changes in the fauna. Since the publication of the first paper quantitative samples have been collected in each of these areas. Taking the survey as a whole, collections have now been made on such widely different parts of the coast that the peculiarities of the distribution of the above two groups can be stated with a fair degree of accuracy. The present paper is divided into two sections, the first dealing with the additional observations, the second with the survey as a whole.

It was the intention of Dr Kidston and myself to deal with the main plant-remains of the Old Red Sandstone of this country in preparation for a systematic account of the flora. I cannot continue the work alone without expressing in affection and gratitude how much I owe to my association with him in it. The loss of Dr Kidston's experience, insight, and judgment in dealing with the obscure and peculiar plants of this early period can hardly be estimated. No further results of our joint work had been prepared for publication; but, since we had for some years made common stock of our observations and notes on the subject, Dr Kidston's views on many points are known to me and will be utilised wherever they apply.

Additional mechanical preparation of the type material of the temnospondyl amphibian Perryella olsoni (Lower Permian, Wellington Formation, Oklahoma) highlights new cranial and postcranial features and provides additional data on previously known structures. Important new information is available for the quadrate, palatal bones and their associated dentition, parasphenoid, and appendicular skeleton. The revised diagnosis and redescription of Perryella provide the basis for a re-evaluation of its systematic affinities. A cladistic analysis of (mostly) Carboniferous and Permian temnospondyls, together with several Devonian and Carboniferous stem tetrapod outgroups, supports a single origin for temnospondyls. The sequence of branching events within temnospondyls consists of: (1) a paraphyletic Edopoidea; (2) a clade of Zatracheidae, Eryopidae, and basal Archegosauriformes; (3) a monophyletic Dvinosauria; and (4) a monophyletic Dissorophoidea. Perryella is nested within Dvinosauria in an intermediate position between Trimerorhachidae and Dvinosauroidea.

A conglomerate test using 36 clast cores (76 specimens) from the upper Precambrian Port Askaid Tillite of the Dalradian Supergroup in the Garvellach–Islay region of Scotland shows that the tillite was remagnetised during orogenic activity in Lower Ordovician time. After 550°C thermal demagnetisation, the clast remanence directions give a mean of 155°, 14° (α95—12°). This is similar to the mean from four tillite matrix sites of 162°, 4° (α95—9°) and the mean ‘primary component direction’ of 166°, −12° (α95—6°) previously determined from the interbedded siltstones. This indicates that the matrix and siltstones were also remagnetised. These mean directions give virtual geomagnetic poles after tilt correction that fall within the cluster of British Ordovician poles from rocks in the Caledonian orogen, and thereby indicate a prefolding Ordovician age for the remagnetisation. Thermal demagnetisation studies and observations from polished and thin sections of tillite clast and matrix specimens show that secondary hematite derived from partially to completely altered magnetite is the dominant carrier of the metamorphic remagnetisation. These results show that remanence data from the Port Askaid Tillite cannot be used to support the hypothesis that a worldwide glaciation occurred during the Late Precambrian.

The richest and more explored regions concerning Miocene crocodylians in South America are the basins surrounding the areas of Urumaco (Venezuela), La Venta (Colombia), Acre (Northwest Brazil) and Paraná (Northeast Argentina). Fossils from the late Miocene in the Paraná area were recovered from the “Conglomerado Osífero” (Ituzaingó Formation) and assigned to several taxa of Caimaninae (Alligatoroidea) and to a taxon of Gavialoidea. The late Miocene “fauna” of crocodylians recorded in northeast Argentina differs from coeval ones of northern South America by the absence of crocodyloids, some alligatorid genera (such as Purussaurus, Melanosuchus, and Paleosuchus) and by the scarce gavialoid species. Giant forms, conspicuous in the northern South American deposits, are also absent in southern latitudes. Despite this, the austral South American crocodylian fauna exhibits strong affinities with the northern, contemporary forms, sharing taxa at generic (i.e. Caiman and Gryposuchus) and even specific levels (i.e. Mourasuchus nativus). The sharing of such freshwater taxa in the Miocene indicates partial connections of drainage basins through swamp areas on their boundaries, and is evidence against the assumption of an intracontinental coeval seaway link in this continent proposed by several authors.

Sixteen new species of trilobites are described and named, and thirty species are figured. The specimens were collected from a small exposure of mudstones at Craighead Quarry; most of the species are only known from this one exposure. The occurrence of several species which show strong affinities with forms from higher horizons indicates that the mudstones are more recent than other Balclatchie Group (Lower Caradocian) deposits.

The study of Organic Form, which we call by Goethe's name of Morphology, is but a portion of that wider Science of Form which deals with the forms assumed by matter under all aspects and conditions, and, in a still wider sense, with Forms which are theoretically imaginable.

The study of Form may be descriptive merely, or it may become analytical. We begin by describing the shape of an object in the simple words of common speech: we end by defining it in the precise language of mathematics; and the one method tends to follow the other in strict scientific order and historical continuity.

Geological and palaeontological research in the Rhynie area, Aberdeenshire, Scotland, has progressed in several stages. Following early surveys in the nineteenth century, Dr William Mackie mapped the western margin of the basin in 1910–1913, and discovered the plant-bearing chert. Following trenching of the chert in 1913, Kidston & Lang described the plant fossils between 1917 and 1921 and Scourfield, Hirst and Maulik the arthropods in the 1920s. Following a ‘dark age’ of some 30 years, Geoffrey Lyon awakened interest in the late 1950s. Trenching in 1963–1971 provided Lyon and his co-workers with new material, and resulted in finds of new plants and reinterpretations of earlier work. The next phase was initiated by Winfried Remy's discovery of gametophytes in material given to him by Lyon. Since 1980, the Münster school has continued to make exciting discoveries. Aberdeen University involvement began in 1987 with geochemical work confirming a hot spring origin for the chert. Drill cores taken in 1988 and 1997, and further trenching have allowed structural, sedimentological and stratigraphic reappraisals, and resulted in the discovery of a new biota in the Windyfield chert. Long-term collaborative international research continues to advance interpretation of this unique Early Devonian hot spring system, and the remarkably diverse freshwater and terrestrial biota of the cherts.

Contact relations and petrography of the volcanic breccia known as the Stac Fada Member, near Stoer, show that it is not a simple sediment-gravity flow, but was generated lower in the sedimentary succession by phreatomagmatic activity and rose to the surface as buoyant peperitic slurry. A previously undescribed part of the member, 9 m below the intrusive base of the main ‘flow’, has an intrusive top. Vesicle trains within the breccia matrix suggest that the slurry was boiling at a temperature of at least 160°C.

Namurian alkali-dolerites in W and central Fife comprise up to nine component sills. These have three-dimensional shapes which are directly related to penecontemporaneous structures in the sedimentary host rocks. Two forms of control are identified. Basinal control is apparent where restored sill geometry shows thickening towards the bottoms of saucer-shapes which mimic sediment disposition at the time of emplacement. Fault control is evidenced by sills which change horizon along extensive E–W fractures once assumed to be entirely post-Carboniferous but now confirmed as growth-faults.

There are no associated dykes representing likely feeders comparable with those of the later tholeiitic Midland Valley Sill, but evidence is presented to suggest that at least some of the alkali-dolerite magma reached sill intrusion levels through volcanic pipes.

The literature of the Scottish Cephalopoda is, on the whole, rather scanty. Most of the references occur in more general faunistic lists, or are comparatively short notices in various periodicals. Except for Russell's work, which dealt almost exclusively with the collections of the former Fishery Board for Scotland and did not include references to the other Scottish species, there is no comprehensive paper devoted to the Scottish Cephalopoda. More attention has been paid to the subject in neighbouring countries. Massy (1928) has summarised previous work on the Irish species; Grimpe (1925) has dealt with the species of the North Sea, and Hertling (1929, 1936) has supplemented Grimpe's work with further notes on the Helgoland species; Grieg (1933) has described the Norwegian forms; Nielsen (1930) has listed the species occurring at the Faroes; Stevenson (1935) has described those found on the Yorkshire coast. Where references are made to the species occurring in the above-mentioned waters, these summaries only are quoted.

The distribution of melt has been mapped in a granite pluton deformed whilst it contained melt. At the outcrop scale, leucomonzogranite melt was segregated from hornblende monzogranite when the rigid crystal framework was tectonically compacted. The melt collected in well-defined, structurally controlled sites that formed during dextral, non-coaxial, strike-slip shearing. The segregations are generally isolated, but locally they link to form extensive branched arrays which drained larger volumes of granite in a two-step process. First, melt drained from the compacting matrix through the array and pooled along dilatant foliation planes; later, the melt moved farther away when a single planar melt-transfer channel formed.

Thin section maps show that most melt was distributed in the foliation plane and along the lineation in the crystallising matrix. The location of melt at the grain scale is primarily controlled by the feldspar-dominated shape fabric of the crystal framework, and not by tectonic stresses as at the outcrop scale. Tectonic stresses account for the relatively small proportion of melt films located in grain boundaries normal to the lineation. The distribution of melt-bearing grain boundaries outlines larger domains in the thin sections that form a linked three-dimensional network through which melt moved within the crystallising framework.

In the following pages two separate subjects are considered which are connected only by their relation to the same animals. The first concerns the feeding mechanisms and habits of the Lophogastridæ, but unfortunately no living animals could be examined.

As a result of some work on the feeding mechanisms of the Malacostraca (Cannon and Manton, 1927, in the press, etc.) it was concluded that in the Syncarida, Peracarida, and Eucarida a primary filter-feeding habit exists. This has been modified or given up entirely in the higher forms of each division in favour of feeding on larger masses of food. In the adult Hemimysis, Anaspides, and Nyctiphanes the filter-feeding mechanisms are essentially similar. The maxilla forms a combined suction pump and filter and draws a current of water through a filtering comb of setæ borne on its proximal endite. This comb is scraped by the basal part of the first trunk limb, which transfers the collected food forwards on to the proximal endite of the maxillule by which it is pushed into the mouth.

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.

A new occurrence of the Hirnantia brachiopod fauna is documented from the Criadero Quartzite of Almadén, Ciudad Real Province, Spain. This unit is the regional development of a largely unfossiliferous sandy facies that frequently overlies the typical Late Ordovician diamictitic glaciomarine formations in the Iberian Peninsula and the Armorican Massif. The new occurrence establishes palaeontologically the latest Ashgill age of the quartzite, at least for its lowest horizons, and adds new data on a fauna that, although widespread, has been very rarely documented from peri-Gondwanan Europe. The new collection contains only Hirnantia sagittifera and Plectothyrella crassicosta chauveli. The subspecific status of the latter and its inclusion within Plectothyrella crassicosta is discussed herein, based on the continuous variation in rib thickness of several samples of both forms. The extremely low diversity and the occurrence of the key form P. c. chauveli, are both typical of the Bani Province that developed on the subpolar margins of Gondwana. This contrasts with other occurrences of the Hirnantia Fauna in peri-Gondwanan Europe, such as those from Sardinia and the Carnic Alps, which are characteristic of the more temperate Kosov Province.

Investigations have been made into the conditions of sedimentation of the Ordovician rocks of the Girvan district, with special attention to a series of greywackes, the Ardwell Beds, which are remarkable for frequent intraformational disturbances and unconformities.

In presenting the evidence it is proposed to follow the stratigraphical classification of Peach and Horne (1899), who, after careful consideration, adopted Lapworth's (1882) succession, except for a few minor alterations. These authors pointed out that the Llandeilo rocks north of the River Stinchar consist of Kirkland Conglomerate, Stinchar Limestone Group, and Benan Conglomerate, while south of the river they are represented by Tappins Greywackes and Glen App Conglomerate (see table p. 488).