Conodontes et Sédimentologie des couches de passage du Givetien au Frasnien dans le Nord du Tafilalt et dans le Ma’der (Maroc Présaharien)

Stratigraphically important conodonts relevant to the Givetian-Frasnian boundary are listed from one section in the Tafilalt area and from threein the Ma'der area. The conodont succession from the Middle Polygnathus varcus Subzone and extending into the Middle Polygnathus asymmetricus Zone is described. The corresponding goniatite sequence ranges from the last occurrence of Maenioceras terebratum into beds containing Manticoceras and Beloceras kayseri. The sedimentology of the beds sampled for conodonts at the Tafilalt section and at two of the Ma'der sections is discussed. The conodont Ancyrodella binodosa is fully described;other relevant taxa are briefly discussed

The lower Carboniferous Brachiopod genus Levitusia Muir-Wood, H.M. and Cooper, G.A., 1960 from Western Europe and the U.S.S.R.

The genus Levitusia MUIR-WOOD, H.M. and COOPER, G.A., 1960 isrevised and details of the shell microstructure are presented enablingthe shell material of Productacea and Chonetacea to be distinguished.The western European species L. burnerosa (SOWERBY, J., 1822), the typespecies (with which L. christiani (DE KONINCK, L., 1847) is placed intosynonymy), L. sublaevis (DE KONINCK, L., 1843) and L. spinauris n. sp.from Staffordshire, England, are described. Species from the U.S.S.R. arediscussed, in particular L. hyperborea from the Urals

Représentants des genres Phillipsastrea d’Orbigny, A. 1849, Billingsastraea Grabau, A.W., 1917 et Iowaphyllum Stumm E.C., 1949 du Frasnien du massif de la Vesdre et la bordure orientale du bassin de Dinant

Thirteen species and subspecies of the genera Phillipsastrea D'ORBIGNY, A., 1849, Billingsastraea GRABAU, A. W., 1917 and Iowaphyllum STUMM, E. C , 1949, collected mainly from the Frasnian of the eastern part of Belgium, are described, figured and placed in their stratigraphic context. A new subspecies, Phillipsastrea ananas veserensis, is defined

Le genre Paraspirifer Wedekind, R., 1926 dans le Dévonien moyen de la partie orientale de l’Amerique du Nord

The authors describe seven species of the genus Paraspirifer WEDEKIND, R., 1926 on the basis of more than one hundred specimens from twenty-three localities in North America. Three of these species are new: P. conradi n. sp., P. halli n. sp. and P. clarkei n. sp. Two others are provisionally named P. cf. halli and P. sp. A. A Neotype is proposed for P. acuminatus (CONRAD, T.A., 1839) and the Lectotype of P. brownockeri (STEWART, G.A., 1927) is designated. The problems concerning the species Terebratula acuminatissima DE CASTELNAU, F., 1843 and Delthyris prora CONRAD, T.A., 1842 are briefly discussed. The genus Paraspirifer is confined to an area of ± 6.500.000 km2 in eastern North America. In New York, the biostratigraphic range-zone for the genus is from the upper Onondaga Limestone (Moorehouse Member) to the middle Marcellus Shale (Solsville Member) and, in Ohio and Ontario, from the upper part of the Columbus Limestone (Zones F — H) to the Silica Shale. In Indiana and Kentucky, the genus occurs in the upper Jeffersonville Limestone (P. acuminatus sensu lato Zone) and, in Illinois and Missouri, in the Grand Tower Limestone

Fixatives, Decalcifiers and Ultrastructure of the organic remnants from mural Nacreous Layers of Fossil Cephalopod Shells

The ultrastructure of the organic remnants has been compared in the TEM, after decalcification of the mural nacre of ammonites and fossil nautiloids by EDTA, which removes a soluble fraction, and after fixation and decalcification by formaldehyde-cetyl-pyridinium chloride-EDTA (CPC method) and chromium sulphate solutions, which are both considered to insure a better preservation of these organic remains. The loose networks of altered trabeculae, frequently fused into membranes, which constitute the ultrastructure of the fossil organic remnants of nacre after decalcification by EDTA, are also found in the samples treated by the CPC method and by chromium sulphate. Continuous membranes, superimposed on the networks, are especially abundant in the material treated by chromium sulphate. It is concluded that the networks of altered trabeculae are not artifacts, but are the representative ultrastructures of the organic remnants of the nacreous layers in the fossils studied so far. It is suggested that disappearance of EDTA soluble substances does not distinctly alter the ultrastructure of the fossil organic residues

Eumetabolotoechia, nouveau genre Rhynchonellide (Brachiopode) du Givetien d’Amerique du Nord

A new genus, Eumetabotoechia, is proposed. It includes three speciesand ranges in age from the end of early to the end of middle Givetian.The type species, Rhynconella (?) Laura BILLINGS, E., 1860, and LeiorhynchusHuronensis NICHOLSON, H.A., 1874 are from the Province of Ontarioin Canada, and L. kelloggi HALL, J., 1867 is from the State of Ohio inthe United States of America

Nouveaux specimens du genre Leclercqia Banks, H.P., Bonamo, P.M. et Grierson, J.D., 1972, du Givetien ( ? ) Du Queensland (Australie)

Axis fragments with « protolepidodendroid » surface pattern from the Middle Devonian (Givetian ?) of the Burdekin Basin (Queensland, Australia)are assigned, following their preparation to the genus Leclercqia,BANKS, H. P., BONAMO, P. M. et GRIERSON, J . D., 1972, formerly restricted to North America