Minute, lamellose concentric micro-frills are described on the external surfaces of the Devonian brachiopod Athyris campomanesi (Verneuil & Archiac). The micro-frills are very regularly spaced with a separation of approximately 0.5 mm, are inclined anteriorly and antero-laterally, and become more or less recurved peripherally down towards the valve surface. These micro-frills must have been secreted by outward extensions of epithelium, presumably resulting from an increase in the rate of cell proliferation or extension in the marginal zone. Extrapolating from the known growth rates of living brachiopods, it seems probable that the micro-frills formed very rapidly, within a matter of days or hours. In life the micro-frills would have formed minute channels around the peripheries of both valves, similar in form and function to rain gutters. As such they probably functioned as baffle chambers, within which excess paniculate material from the inhalant feeding currents would have accumulated. Such particulate material is likely to have been moved laterally from the median axis of the shell down to the sediment surface under the effects of gravity and in vitro shell movements. Each micro-frill may only have functioned in this fashion for a matter of weeks before being rendered ineffective by the forward growth of the valve margin, at which stage it would have been abandoned and replaced by a subsequently formed micro-frill.

Fifteen specimens of Eristophyton stems from the Lower Carboniferous Cementstone Group of Berwickshire and East Lothian have been examined. Three possess medullary rays comparable to E. waltonii Lacey, the others have rays like E. beinertianum (Göpp.) Zalessky. In one specimen assigned to E. waltonii a leaf-trace subdivides outside the secondary xylem to form an arc of six separate bundles. Another stem of E. waltonii has attached closely spaced petiole bases one of which is clearly identifiable as Lyginorachis with six vascular bundles arranged in an arc. Stems of Eristophyton from five localities occur associated with petioles or rachises possessing a U-shaped vascular bundle with abaxial ridges like L. waltonii Calder. As these may occur mixed with rachises agreeing with L. brownii Calder the latter is regarded as synonymous. Detached petioles found associated with E. beinertianum may possess four or six basal bundles. The evidence suggests that the U-shaped petiolar bundle passes down into four then six basal bundles and such petioles are associated with both E. waltonii and E. beinertianum. Calder (1935, pl. 1, fig. 2) showed dichotomy in the petiole bundle.

In addition different rachises are known possessing a more massive U-shaped bundle but lacking sclerotic nests and sparganum outer cortex. These are assigned to Cladoxylon edromense sp. nov. Cortical nests occur in both E. waltonii and L. waltonii and may be compared with the sclerotic plates in the compressions of Diplotmema dissectum Brongn. and D. patentissimum Ett.. The evidence supports the view that Eristophyton is a pteridosperm with bifurcate fronds known as L. waltonii Calder when petrified and comparable to Diplotmema when compressed.

Pipe-shaped breccia bodies associated with diorite intrusions are composed mainly of angular clasts of local schists with a few transported clasts of quartzite. Plate shaped fragments are commonly oriented to define planar fabrics in the breccias. These features indicate the operation of gas fluidisation within the pipes and both entrainment and expanded bed conditions are inferred. The fabrics result from the collapse of the fluidised suspensions as the gas flow declined. Dilational fracture patterns in the country rock comparable with the stress release patterns found around mine shafts can be matched with the fractures required to produce the angular schist clasts. It is concluded that fracturing and the introduction of fragments into the fluidised breccia system was a continuous process and that the pipe diameter increased progressively with time. Microdiorite sheets and related stock like bodies of diorite cut and metamorphose the breccias. Compaction, hornfelsing and hydrothermal alteration also contributed to breccia formation.

The dimensional statistics and proximal development characters of the Llanvirnian pendent didymograptid D. murchisoni are defined using the type material from near Builth Wells (Powys) and other collections from Abereiddi Bay (Dyfed). Population variability (as expressed by variation coefficients) in the undeformed faunas amounts to about 10% for the sicula lengths and thecal spacings, but is over 20% (up to 200%) for stipe lengths and divergences. Characters with low variability have greater species-diagnostic value. Proximal development in the species involves a dicalycal th 11 and a low origin for that theca from the sicula. The taxa Didymograptus amplus, D. nanus, D. geminus, D. geminus latus and D. acutus are varieties within populations of D. murchisoni and are therefore junior synonyms.

The resulting rationalised taxonomy allows advances to be made in the use of the species in stratigraphy and tectonics. For example, an occurrence of undeformed (pyritised) D. murchisoni in full relief at Abereiddi in the same beds as flattened and deformed faunas, allows a calculation of the absolute three-dimensional strains to be made for the slates there. The strains are strongly flattening (K < 0 · 3) and involve volume changes of about −56%. The high dilatation values imply that stylolite and grain-boundary pressure solution operated during the deformations to take the changes in volume beyond what is possible with simple compaction (i.e. porosity reduction).

The quartz-sillimanite-garnet rocks of the Precambrian khondalite assemblage of Orissa consist dominantly of SiO2 + Al2O3 + Fe2O3 + FeO (average c. 95%) with Fe2O3 > FeO. An average analysis (H2O and CO2 free) also shows MgO, CaO and Na2O having 1·0, 0·5 and 0·4%, respectively. Compared with average crustal abundances, enrichment is shown in SiO2, Al2O3 and Fetot and depletion shown in MgO, CaO, Na2O and P2O5 with that for CaO being more than an order of magnitude and that for Na2O being a factor of >7. On an SiO2–Al2O3–Fetot plot a clearly defined field, elongate nearly parallel to the SiO2–Al2O3 sideline, is similar to that for deeply weathered soil profiles in Brazil. This correspondence also extends to enrichment, stability or depletion, compared to crustal averages, for Ce, Co, Cu, Ga, La, Ni, Nb, Th, U, Y, Zn and Zr, but not for Ba, Cr and Rb. In addition comparison of the proportions and ratios of alkalis and alkaline earths in average khondalite and in a weathering profile over a granodiorite, considered to be typical of the weathering of continents, shows remarkable similarities.

The major and trace element data are consistent with the khondalites being granulite facies—upper amphibolite facies metamorphic equivalents of a deeply weathered soil profile. Associated quartzites and calc-silicate granulites are interpreted as having been silcretes and calcretes, respectively. This interpretation implies (1) the previous existence of a large stable cratonic mass on which the soil profile formed, (2) climatic conditions suitable for the development of such a profile, (3) topography, drainage systems and groundwater movement in Precambrian times similar to those of present day peneplane regions, (4) the presence of free oxygen in the atmosphere, (5) rapid covering (e.g. by products of volcanism) to preclude mass wasting, (6) a Precambrian stratigraphy in the crystalline rocks of the Eastern Ghats region similar to that of South India, and (7) orogenesis that involved tectonic repetition of lithological units and a mechanism for taking products of surface weathering down to granulite facies P–T conditions and subsequently elevating them.