Late Caradoc-early Ashgill trilobites of the central Oslo Region, Norway

38 trilobite species belonging to 31 genera are described from the late Caradoc - early Ashgill Upper Chasmops Limestone and Solvang Formation in Oslo-Asker, Ringerike, and Hadeland. The following species are new: Mesotaphraspis bockeliei, Dionide magnifica, and Staurocephalus pilafrons. A lectotype is chosen for Ampyxella aculeata (Angelin) and Angelin's original specimens of Lichas sexspinus, a synonym of Platylichas laxatus (McCoy), are refigured. The Swedish species Stenopareia avus (Holm, 1886) is considered a junior subjective synonym of S. gaber (Kjerulf, 1865) and original material of both is figured along with Swedish material of S. linnarssoni (Holm), S. oviformis (Warburg), and Illaenus ( Parillaenus) roemeri Volborth.