Abstract
The history of research on the Ordovician rocks of Portugal is briefly outlined and the biostratigraphy of different regions is reviewed. Ten stratigraphic columns are presented for selected areas and the lithological and faunal characteristics are described. The trilobites belong to the Selenopeltis province and evidence is given for the recognition of two faunal subprovinces (termed associations by Henry 1980) in north and central Portugal during the Arenig to Llandeilo. The current state of knowledge of Ordovician palaeogeography in Portugal is discussed and maps are presented for the Arenig and Llandeilo Series.