Conodonts are present throughout the Lower Ordovician Huk Formation (previously the 'Orthoceras Limestone') at Slemmestad, southern Norway. Forty-one samples from the 8.6 m thick Huk Formation and the overlying 1.2 m thick Helskjer Member of the Elnes Formation were processed and yielded 5136 conodont elements of which 4963 were identifiable. Eighteen genera and 34 species are present. Drepanoistodus stougei n.sp. is described and taxonomic notes are included. The Huk Formation comprises, in ascending order, four conodont zones: The B. navis, P. originalis, M. par va and E. ? variabilis zones, although only the E. ? variabilis-M. parva Subzone of the latter zone is present. It is suggested that the Arenig-Llanvirn boundary is situated within the lowest 1 m of the Svartodden Member, the uppermost member of the Huk Formation.

Jan Audun Rasmussen, Institute of Historical Geology and Palaeontology, University of Copenhagen, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark.