The Foulden Site of Special Scientific Interest is one of the few Cementstone Group localities that yields significant fauna and flora. Excavations in 1980 and 1981 removed a 1·3 m2 slab of the Fish Bed for laboratory study of the vertical and spatial distribution of the biota. Layer by layer analysis revealed an almost mutually exclusive relationship between the vertical distribution of the palaeoniscoid fishes and malacostracan crustaceans, as well as a horizon crowded with juvenile acanthodians. Elongate elements of this biota showed slight preferred orientations at that prolific horizon. Some 27 m of strata including the Fish Bed, Plant Bed and Shell Bed are recorded in detail, and their biota noted. Interim results of work on the main groups collected are summarised in associated papers in this part of Transactions. Brief reports are given here on the euryhaline marine bivalve mollusc Modiolus latus (Portlock), a rare durophagous bradyodont shark tooth and an Eogyrinus-like amphibian scute.

The migmatitic gneiss complex of Lylyvaara in the eastern part of Finnish Presvecokarelides of the Baltic Shield shows evidence of a polyphase deformational and metamorphic history and of the emplacement of a number of mafic and felsic igneous intrusions at various stages during this history. Sequential structural development has been established on the bases of refolding and cross-cutting relationships. U–Pb zircon and sphene isotopic data combined with structural studies indicate that the first six deformational phases took place in late Archaean (=Presvecokarelian) times. The seventh deformational phase is constrained as being early Proterozoic (=Svecokarelian) from regional considerations.

The gneissic foliation in the dominant tonalitic to trondhjemitic palaeosome is parallel to lithological layering (So). Mostly it is composite S1–S2; only in F2 fold hinges can separate S1 and S2 be unequivocally distinguished. There, both of these fabrics, which were formed in amphibolite facies conditions of metamorphism during D1 and D2 have retained their identity despite extensive tectonic overprinting. Further tonalitic or granodioritic material was intruded during D3 or between D2 and D3. Effects of the third deformational phase (D3) ar6e expressed only locally as asymmetrical and polyclinal folds, which deform S1–S2 and F2. These folds now have a northeasterly axial trend and they show considerable variations in the style of their parasitic structures. F4 folds are common. They are dextral and asymmetrical, have NW—NNW-trending axes and show complex interference patterns with F2 and F3 folds. During D4, much aplogranitic neosome material was emplaced in NW—SE-trending movement zones, which correspond to the axial planes of F4 folds. Superimposition of F5 and F6 structures on previously formed patterns add to the structural complexity although they only result in minor modifications. Both are open and upright and locally have associated cleavages or healed fractures (S5, S6). D7 is expressed throughout the migmatitic complex as narrow NW—SE-trending shear zones which reactivate the S4 trend.

U–Pb zircon isotopic data indicate that the metamorphism associated with gneiss formation took place 2843 ± 18 Ma ago. U–Pb sphene ages of c. 2660 Ma and 2620 Ma indicate that metamorphic conditions prevailed for a very considerable time. An aplogranitic neosome related to F4 axial planes gave a 2657 ± 32 Ma U–Pb zircon age, while granodiorite and pegmatite dykes related to D6 yielded U–Pb zircon ages of c 2670 Ma and 2640 Ma, respectively.

Branchiopods are primitive crustaceans whose history extends back at least to the Devonian, yet some are highly successful today. Most fossil branchiopods do not show many features that lead to an understanding of function, but the Devonian lipostracan Lepidocaris is an exception. Recent work on living branchiopods, especially anostracans and anomopod cladocerans, enables Lepidocaris to be considered as a living animal. Work on extant anostracan nauplii also makes it possible to deduce how its larval stages swam and collected food.

Other early crustaceans are briefly considered and comments are made on the concept of “living fossils”. While rates of morphological and genomic evolution are often discordant, the concept is still useful. Some branchiopods, such as the Notostraca, display remarkable morphological stasis: on the basis of morphology, a Triassic and a present-day form appear to be conspecific. The latter may be referred to as a “living fossil”.

The outstanding morphological stasis of the crustacean nauplius is noted. Its existence in Cambrian times, deducible from its distribution among modern taxa, has been confirmed by Müller's finds. Such stasis, involving part of the genome of organisms whose adults display enormous adaptive radiation, has persisted with relatively small modifications since before the commencement of the entire radiation of vertebrates.

This study attempts to ascertain whether the differing provenance sources and plate tectonic settings of deposition of clastic sediments and rocks can be identified by chemical means, thus opening the increased use of these rocks and their metamorphosed derivatives in plate tectonic modelling. Mineralogically immature feldspathic and mafic sands, muds, sandstones and shales from Mesozoic, Cenozoic and Holocene clastic deposits in California, Oregon, Alaska and Colorado have been both modally and chemically analysed providing a valuable data base (217 samples; 216 samples chemically analysed, many for 28 elements).

There is significant upward chemical variation in the Great Valley sequence of California which mimics previously described petrographic variation and in turn reflects provenance changes with igneous episodes and erosional stripping of the Sierra Nevada in late Mesozoic time. Differing sandstone petrofacies result in varying chemical signatures and while the provenances of monomict sediments are easiest to identify, polymict sources involving granitoid or ophiolitic material can often be identified by potassium feldspar or Cr contents. The distinction of K which is derived from detrital potassium feldspar from K derived from detrital illite, micas or other sheet minerals, is best made by a Niggli al–alk plot against k. Mafic sandstones derived from mafic volcanic or plutonic rocks preserve essentially mafic igneous chemistry and could be possible parent sources of some amphibolites which grade into metasediments. The lithified erosion products of the Sierra Nevada calc-alkaline igneous rocks have higher Niggli al–alk and higher average Niggli si at any given mg value than the fresh igneous rocks enabling meta-arkoses to be distinguished from meta-igneous rocks.

Applying previously published chemical criteria gives the actual plate tectonic setting of deposition of most of the sandstones studied. This suggests that the chemical composition of sandstones can yield much more information about the provenance and plate tectonic setting than hitherto recognised.

The Berwickshire Cementstone Group was deposited on a coastal plain crossed by meandering rivers flowing S into a marine gulf, the Northumberland basin. Sedimentation was mainly by overbank flooding onto an alluvial plain which largely dried out between floods. The resulting sediments include poorly-stratified mudstones and siltstones and crevasse splay sheet sandstones. The depositional environment of the cementstones is not clear. Lacustrine and tidal flat origins are considered. Semi-permanent floodplain lakes were very rare, but in one the uniquely fossiliferous Foulden Fish Bed was deposited. This lake was shallow and filled by repeated influxes of sediment carried from rivers by sheetfloods. On entering the lake, these sheetfloods may have become density underflows from which thin, graded siltstones or sandstones were deposited. These floods carried plant debris into the lake and rapidly buried the remains of the lake fauna. The salinity of the lake cannot be determined, but the input of both fresh and saline waters can be envisaged. There is no evidence that the lake was permanently eutrophic. The mortality of the animals may have been due to changes in water chemistry produced by hot dry spells of weather followed by storms and floods.

Anatomically preserved plants are recorded from calcareous nodules and include Lepidodendron calamopsoides Long which demonstrate for the first time the presence of anisotomous branching, in addition to the normal isotomous branching and details of the stele and the cortex seen in longitudinal section. The nodules also contain Setispora subpaleocristatus (Alvin) Spinner and Lagenicula crassiaculeata Zerndt megaspores. There is an abundant compression flora. Compressions and petrifactions of Tristichia ovensi Long may not represent the same plant and may not be connected to Stamnostoma huttonense Long. We suggest that the compressions of T. ovensi were of a pteridospermous plant with unlaminated fronds bearing small uncupulate seeds and lateral clusters of microsporangiate organs of a new type.

Sedimentary basins are structures that formed either by subsidence of an area relative to its surroundings, or by uplift of the surroundings. The basin is defined by its sedimentary fill, and the vertical kinematics of the fill are reflected by stratal wedging, unconformities and, or, faulting. The following basin mechanisms are distinguished: locally (a) stretch, (b) thrust and piggy-back, (c) local uplift, and regionally (d) stretch-and-cool, (e) load-and-flex and (f) cratonic uplift.

Basin patterns are reviewed for the three main Phanerozoic episodes for which molasse-like features of sedimentation or tectonics are claimed. Sediment accumulation rates are used as an index of the vigour of basinal activity.

Within the area of the Caledonian orogen, Devonian basinal activity was locally very rigorous, some of it being late orogenic and some post-orogenic, and mostly apparently of ‘stretch-type’. The orogenic area stood high, relative to sea level, throughout Devonian times, but outside the orogenic area, the basins were less vigorous and marine.

Within the area of the Hercynian orogen, and outside it, Permian basins were generally not so active, apparently reflecting a different style of orogenesis. However, the whole area was standing high, relative to sea level. The Triassic basins, though post-orogenic, were rather more vigorous, although a marine transgression records the general lowering of the continental surface. Major evaporites accumulated in these settings.

In Cenozoic times, the narrow orogenic belts formed the most active basins, and these were of load-and-flex type, reflecting the importance of thrust-sheet movement, itself perhaps a result of the presence of Triassic evaporites. Other non-orogenic basins reflect both ‘stretch’ and ‘stretch-and-cool’ mechanisms. Only the Spanish basins appear to have been standing high, relative to sea level, perhaps in response to cratonic uplift.

An analysis of swimming in living crustaceans is presented in order to elucidate the range of ways this function has been achieved, and to reveal the principles which constrain it. The study focuses on Gnathophausia ingens, a primitive, bathypelagic malacostracan that swims with thoracic exopods and pleopods. These structures consist of a muscular peduncle and one or two flagella that are fringed with setulate setae. The basic motion is rowing with the limb and setal fan extended on the power stroke and flexed on recovery.

A survey of other crustaceans shows that rowing with this type of swimming structure dominates throughout, although paddles often replace the flagella. Particularly pervasive is the large relative area of setae, whose effectiveness must stem from the ability to extend and flex passively and from the high drag generated on the power stroke by the setules at low Reynolds numbers.

A review of reconstructions of Palaeozoic trilobites and marrellomorphs reveals the likelihood that if swimming was the function of the exites, they operated inefficiently or were employed in other methods as well. Sculling and drag reduction on the recovery stroke through feathering rather than flexion are possible alternatives. The more common occurrence of paddle-like limb shafts and blade-like marginal structures in other Palaeozoic arthropods is also noted.

Living Crustacea possess many types of sensory receptors that detect environmental signals. These structures allow the speculation that similar organs existed in fossil arthropods and were involved in similar ways in the fossil forms when they were extant.

Posture, for example, is difficult to reconstruct in fossils without the understanding that internal proprioceptors monitoring position and movement are crucial in determining the placement of limbs, and the position of the abdomen and other jointed portions of the body. These receptors are associated also with autotomy reflexes through soft cuticle detectors that respond to strain not associated with joints.

Many receptors are placed on the outer surface of the animal, the eyes being the most obvious. The eyes receive no attention in this paper, but descriptions are given of a number of different types of setae, serving both mechanical and chemical sensors. The possession of a pore at the apex (or sub-apex) of a seta or setule probably indicates a chemoreceptor function, but its absence does not necessarily indicate a lack of such sensitivity. A range of forms is illustrated.

The dorsal organ is a recently discovered structure in decapod larvae. It is composed of a central single gland cell opening via an aperture in the midline just behind the rostrum. It is bounded by four depressions each containing a central ‘nipple’. These prove to be sensors, with ciliated endings (bifid) that end in a highly modified cuticle at the depression nipple. The function is unknown, but it is proposed that it represents an unusual chemoreceptor.

Plant miospore assemblages obtained from eight beds of the Foulden sequence, ranging from Bed 1 to Bed 17, are basically similar to each other in stratigraphical significance. The presence of Convolutispora circumvallata, Crassispora trychera and Schopfltes claviger and the absence of Lycospora pusilla suggest assignment to the Schopfites claviger-Auroraspora macra (CM) Biozone. This indicates the Courceyan Stage of the British Dinantian and the late Tournaisian (Tn3) of the Belgian Series. Comparable miospore assemblages have been described from Cementstone Group localities elsewhere in Berwickshire, East Lothian, Ayrshire and northern England. Preservation, and lack of marine palynomorphs and scolecodonts, suggest non-marine deposition. The presence of vitrinite fragments and megaspores as well as miospore tetrads suggests little transport before deposition.

This paper describes the suture zone between the Asian plate and the accreted Kohistan island arc in the Chitral district of NW Pakistan.

The southern part of the Asian plate consists of two tectonic units separated by the N-dipping Reshun fault. The northwestern unit comprises Devonian carbonates and quartzites overlain by Devonian to Permian shales and slates with some limestones (Lun shales). Its structure is complex with S-verging thrusts and isoclinal folds. Along the Reshun fault, the relatively undeformed Reshun Formation may represent molasse. The central unit includes N-dipping Upper Palaeozoic slates and quartzites (Darkot Group), probably faulted against an antiformal tract of slates, schists derived from a volcanic assemblage and Cretaceous limestones (Chitral slate, Koghozi greenschist, Krinj and Gahiret limestones). Asian plate sediments are intruded by granitic and granodioritic plutons, variably deformed and locally porphyritic.

The Northern suture melange of volcanic, sedimentary and serpentinite blocks in a slate matrix separates the Asian plate from the southeastern unit, the Kohistan arc. This comprises Cretaceous volcanic rocks with some sediments (Shamran Volcanic Group, Drosh, Purit and Gawuch Formations) intruded by aphyric diorites, tonalites and granites. These intermediate plutonic rocks pass southwards into a mafic layered complex and amphibolites representing deep levels of the arc. The volcanic rocks and sediments dip to the N and have a horizontal lineation. The structural history of southern Asia and Kohistan is consistent with an originally curved Northern suture: motion of the arc was initially to the NE relative to Asia and subsequently to the NW.

A survey is given of the functional morphology of extant Chelicerata with special reference to segmentation of the body, segmentation and articulation of the legs, coxal glands, mouthparts and ingestion, respiratory organs, sperm transfer, and development. This is followed by a discussion of primitive types, evolution and diversity, the transition from aquatic to terrestrial life, and the affinities of extant chelicerate groups.

A diverse, but sparsely distributed silicified fauna of over 30 taxa has been recovered from 7·5 tonnes of acid-etched Lower Ordovician Dounans Limestone from the Highland Border Complex, near Aberfoyle. The 13 trilobite taxa obtained include 3 new formally named species: Distazeris adoceta, Punka aetholiciocorus and Ischyrotoma stubblefieldi. Other elements, representing Carolinites, Illaenus, Goniotelina, Sycophantia, Kawina, Heliomeroides, Strotactinus, Ectenonotus, Ceratocephala and an indeterminate bathyurelline are described under open nomenclature although at least 4 are also probably new and 2 more may be conspecific with previously described species. The brachiopods include representatives of Archaeorthis, Nothorthis, Orthidium, ?Camerella, Idiostrophia, Orthambonites and 4 other indeterminate stocks. Gastropods tentatively assigned to Murchisonia, Subulites, Straparollina, Maclurites and Cyrtodiscus are described, as are bryozoans, an orthocone, crinoids, and Incertae sedis.

This profoundly North American fauna is Late Canadian ( = mid Arenig) in age and equates with the Cassinian Stage: it is key evidence in showing that the Highland Border rocks are not part of the Dalradian Supergroup whose earliest deformations and metamorphism predate the Ordovician. The field relationships of the limestone, together with evidence from derived clasts in Middle Ordovician and Devonian sequences near Girvan in SW Scotland and at Stonehaven in eastern Scotland suggest that it forms part of a widespread sub-Old Red Sandstone carbonate sequence of Early Ordovician age beneath the northern Midland Valley.

A lower Carboniferous limulacean Rolfeia fouldenensis gen. et sp. nov. is described. It is regarded as a sister group of Paleolimulus and distinguished from it by the presence of fixed opisthosomal spines and by the more primitive outline of the opisthosoma. Both characters could have been derived from belinuroid ancestors, and both were retained in the advanced belinurids and euproopids. The view that limulaceans are more closely related to certain primitive belinuraceans rather than descended from the euproopaceans is thus supported by the new evidence. Although Rolfeia was probably still capable of coaption, it is postulated that, like other limulaceans, it had adopted burial as a form of defence. It is suggested that the primary adaptive function of the fixed opisthosomal spines was to support the body over a soft substrate although they may also have served a defensive role.

The occurrence at Foulden of the eurypterid Cyrtoctenus peachi Størmer and Waterston is confirmed. The eoscorpiid Trachyscorpio squarrosus Kjellesvig-Waering 1984 has been described from Foulden and disjecta membra of Gigantoscorpio cf. willsi Størmer discovered in the recent excavation are described. The type of preservation and adaptive features of the chelicerates would suggest that the eurypterid and scorpion fragments are allochthonous and the xiphosurans probably autochthonous.

The modes of life of twenty three species of arthropods from the Shale are reviewed, with special reference to locomotion and feeding. Six groups are recognised, predatory and scavenging benthos, deposit-feeding benthos, scavenging and possibly predatory nektobenthos, deposit-feeding and scavenging nektobenthos, nektonic filter-feeders, and a miscellaneous sixth group that includes a questionable example of parasitism and a species that doubtfully grazed on algae. These animals had but limited powers of walking, digging, raking or swimming. Within these limitations a range of morphological adaptations and modes of feeding had been evolved, by Middle Cambrian time, a range comparable to that found in Recent marine forms. Arthropods in the Shale dominated, in numbers of individuals and possibly in biomass, a fauna dwelling above, on and in a muddy substrate at a depth of about 100 m.

Chemostratigraphical correlation provides valuable insights into the status of the Colonsay Group, which field and structural studies have left unresolved. Using published discriminant functions, major and trace element data support previously proposed correlations of the Colonsay Limestone with Appin Group (Lower Dalradian) limestones, and particularly with the Ballachulish Limestone Formation. They also tend to preclude correlations with other nearby Dalradian carbonate formations, with marbles of the early Precambrian Lewisian complex, and with miscellaneous unassigned limestones in a similar structural position to the Colonsay Limestone, astride the Great Glen fault.

The Tealliocaris and Crangopsis previously recorded from Foulden are shown to be Bairdops elegans and Belotelson traquairi, respectively. This locality thus yields the oldest Known Bairdops. The two species are confined to the lower Carboniferous sedimentary basin S of the Southern Uplands massif. Elsewhere, these genera are thought to characterise the nearshore marine fauna. The reciprocal relationship noted between malacostracans and actinopterygians may therefore be a function of fluctuating salinity.

Extensive preparation since 1975 has yielded thousands of specimens of various minute arthropods, mainly phosphatocopid ostracods and other crustaceans. The whole exoskeleton is exceedingly well preserved in three dimensions, showing even delicate mo1 phological details. The material permits not only the description of the morphology and systematic status of the animals but also interpretation, with a high degree of confidence, of the function, life habit, and ontogeny of these early arthropods.