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The external surface of Dictyonella is characterized by a smooth depressed umbonal region and a pitted ornament. The exposed part of the smooth plate, here termed the colleplax, is enlarged by resorption of the outer shell. A model is developed to explain the mode of function of the colleplax and its relationships to the soft tissue. The apparently complicated surface pattern of Dictyonella and other pitted brachiopods is shown to be produced by simple radial growth modified by various factors.

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Euhystrichoceras Spath, 1923, Algericeras Spath, 1925, of which Prionocydoides Spath, 1925 is regarded as a synonym and Sakondryella Collignon, 1964 a subgenus, are the last, Cenomanian, members of the typically Upper Albian subfamily Mortoniceratinae. They are believed to have evolved from the diminutive Cantabrigites Spath, 1932 and are diminutive taxa of paedomorphic origin. The type and other poorly understood species are revised and a new species, Euhystrichoceras baylissi, the largest and youngest known, is described from the Upper Cenomanian of Devon.

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Broomia perplexa is a primitive sauropsid reptile from the Middle Permian of South Africa. Preparation of the type specimen indicates that Watson's original description was in error in describing features of palate, carpus, and tarsus that appeared to distinguish the specimen from other primitive reptiles. Broomia is a millerettid, apparently descended directly from the romeriid captorhinomorphs. It is considerably older than other millerettids, and so is of considerable evolutionary and taxononnc importance.

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The morphology and stratigraphic importance of species, subspecies and varieties of the genus Gavelinella from the Senonian (Upper Cretaceous) chalk of north-west Europe are discussed. It is suggested that several stratigraphically significant lineages arose from a Gavelinella schloenbachi (Reuss) ancestor during the Senonian. Within the Gavelinella clementiana (d'Orbigny) plexus of evolving forms, one subspecies G. dementiana convexa is described as new. The Gavelinella lorneiana (d'Orbigny)-G.

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The bioherms and biostromes of the Forteau Formation in southern Labrador and western Newfoundland are rich in archaeocyathans. The older bioherms contain five genera and six species while only three genera and three species are found in the younger biostromes. Metaldetes profundus, which constitutes up to 80% of the fauna in both horizons, exhibits a great variability in growth form, ranging from stick-like to cup-like to plate-like in shape. The other taxa present are ?Metaldetes simpliporus (sp. nov.), Archaeocyathus atlanticus, Archaeosycon billingsi and Arrythmocricus kobluki (gen.

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Early Lower Cretaceous (Berriasian-Hauterivian) ammonite faunas in north-west Europe were predominantly of boreal origin. However, during Valanginian and Hauterivian times there was strong Tethyan influence. The most sharply defined immigration horizons (earliest Valanginian, early late Valanginian and mid Hauterivian) coincide with significant transgressions. Some species came singly or in small numbers, while others migrated in large numbers to evolve into thriving populations which sometimes gave rise to endemic genera.

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Cryptostomes, principally of the suborders Fenestelloidea and Rhabdomesina. dominated Carboniferous ectoproct bryozoan assemblages. Cystoporates and trepostomes were generally less diverse and less numerous. The bryozoan faunas occurred in eleven geographic regions during the Tournaisian, Visean, Namurian A. Namurian B and C, Westphalian. and Stephanian. Early Carboniferous bryozoans rapidly evolved from Devonian stocks. Visean generic assemblages are highly diverse, abundant, and widespread.

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Stromatolites from the Hearne Formation exhibit several orders of finely preserved laminae. This lamination has previously been interpreted in terms of daily, fortnightly, monthly, and annual periodicities, the ratios of which have been used to estimate a past rate of the Earth's rotation. Parallels between Hearne Formation stromatolites and certain Recent algal mats suggest, however, that the finest Hearne Formation laminae may reflect episodes of storm sedimentation, while the second order of lamination represents seasonal maxima in algal productivity.

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An articulated specimen of a vagile metazoan with at least twelve similar, calcitic, dorsal skeletal sclerites is described from the Hemse Beds (Silurian, Ludlow Series) of Gotland, Sweden, as Selenoplax ogmota gen. et sp. nov. In thin section, a sclerite shows a microstructure of posteriorly radiating, interfering spherulitic cones of calcite with fine growth lamellae; the original composition can be inferred to have been calcitic. Suprageneric taxonomic relationships are assessed but as yet it is not possible to assign the genus to any known phylum.

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Several points in the anatomy of Rhabdoderma are reinterpreted based on three-dimensional specimens from the Upper Carboniferous of Great Britain. It is shown that Rhabdoderma does not possess a basipterygoid process, and that the otico-occipital division of the braincase is completely ossified, with no trace of separate ossification centres. Rhabdoderma is distinguished from other coelacanths by the shape of the first dorsal fin support and the pattern of ornament on the scales. Emended diagnoses are given of the five British species considered as valid.

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