Cornelis J. Veltkamp

ISOTOPE DATA FROM CRETACEOUS CHALKS AND FORAMINIFERA: ENVIRONMENTAL OR DIAGENETIC SIGNALS?

Scanning electron microscopy of sediments, microfossils, and polished thin sections from the Cenomanian-Turonian boundary section at Dover, England, demonstrates that cement is concentrated within large pores such as foraminifera and calcispheres, whereas the surrounding coccolith-rich sediments are largely lacking in cement. Isotope analysis of single microfossils and cement samples indicates the presence of mixing lines between primary (paleoceanographic) compositions and cements. Consequently, paleoceanographic and stratigraphic interpretations of these sediments, and perhaps other similar sediments based on similar data, may be suspect.

THE ANTILLEAN TERTIARY CRINOID FAUNA

Abstract Fossil crinoids are described from the Lesser Antilles for the first time. Crinoids are now known to occur in the Miocene of Carriacou, the Grenadines (four species), and in the Eocene and Miocene of Barbados (three species). Taxa include: isocrinid sp. indet., hyocrinid sp. indet. (both Eocene); the isocrinids Neocrinus decorus (Wyville Thomson, 1864) and Isocrinus sp., the bourgueticrinid Democrinus? sp., and the comatulid Horaeometra sp. (all Miocene). Despite the preponderance of taxa in open nomenclature, these are among the very few records of fossil crinoids from the Antillean region. Faunas are dominated by the columnals of isocrinids; bourgueticrinid and millericrinid columnals, and comatulid centrodorsals, are very rare, despite comatulids being both the most diverse crinoids in the modern fauna and the only group that occurs in shallow-water environments. Post-Eocene crinoid faunas in the Antillean region include taxa that are similar, at least at the generic level, to those of the present day. Democrinus? sp. from Carriacou is the first pre-Quaternary bourgueticrinid from the Antilles. Horaeometra sp. is the first fossil comatulid from the Antilles to be classified to generic level. The extant crinoid fauna of the tropical western Atlantic includes 23 genera/34 species of “stalkless” comatulid crinoids and eight genera/ten species of stalked crinoids. This is far greater than the known diversity of fossil crinoids from the Antillean region, which spans circa 120 Ma. The apparent rarity of fossil crinoids is probably part artefact, produced by collection bias, taphonomic effects, and the relative rarity of exposures of sedimentary units deposited in 150+ m, i.e., the environment of extant stalked crinoids.

Barycrinus (Crinoidea) from the Lower Carboniferous of England

The Early Carboniferous (Mississippian) cyathocrinine cladid crinoid Barycrinus, which is common in North America, has hitherto been recognized from Britain only on the evidence of one species, Barycrinus ribblesdalensis (Wright), based on rare dorsal cups. Barycrinus sp. pluricolumnals and plurimeres are common in the Salthill Cap Beds (Chadian), Salthill Quarry, Clitheroe, Lancashire, but are not conspecific with B. ribblesdalensis. Salthill ossicles are never preserved as individual columnals due to the relative weakness of the intermeric versus the longitudinal ligaments.

Ultrastructure of infection of excized leaves of celery by Septoria apiicola, causal agent of leaf spot disease

The growth of Septoria apiicola was observed by SEM on excized celery leaves and on agar medium. Initial germ tube growth was random over leaf surfaces and closely appressed to the cuticle. Leaf penetration occurred directly through the epidermis and also via stomata. After infection, hyphal growth was restricted to intercellular spaces at first but became extensive later. Limited intracellular penetration was observed when leaves were necrotic. Development of pycnidia was observed in detail in leaf tissue and on agar.

The micromorphic articulate brachiopod Gwynia from the Western Approaches, UK

The micromorphic brachiopod genus Gwynia was established by William King (1859) on the basis of specimens described by Gwyn Jeffreys (1859) from the coast of Normandy and Belfast Lough. Additional, unpublished records of the genus from Larne and Portrush, collected by Dickie, Hyndman and Waller during the 1850s, were the last sightings of the taxon around Ireland (Massy, 1925). Despite the distinctive characteristics of the genus, Davidson (1861, p. 39) considered it had yet to be sufficiently determined whereas others (see Brunton and Curry, 1979, p. 46) have suggested the genus may be an immature form of Argyrotheca cistellula (Searles-Wood) with which Gwynia often co-occurs. However, that species is consistently transverse with marked exopunctae.

Significance of diadematid echinoid ossicles in micropalaeontological samples, Miocene–Pliocene of Indonesia

Fragments of diadematoid echinoids from the early and middle Miocene, and late Miocene–Pliocene, respectively, of Java, Kalimantan and Sulawesi, Indonesia, are identified as diadematid spp. indet. (radioles from all sites) and Centrostephanus sp. (an interambulacral plate; early Miocene, Java). The radioles are probably a mixture of Diadema ± Centrostephanus ± Echinothrix. This is the first report of identifiable fossil diadematoid remains from Indonesia and demonstrates that these echinoids, so common in modern reef environments, were present in the Neogene of the region. Even though classified in open nomenclature, Centrostephanus sp. nevertheless provides further evidence for the Cenozoic record of a genus in which the only nominal species are of Late Cretaceous and Holocene age.