The biostratigraphic ranges of three important brachiopod lineages are described from the central and
southern Oslo region. Transitions between the various subspecies of Stricklandia, between Stricklandia
and Costistricklandia, and between Pentamerus and Pentameroides are refined in several districts. The
transition between Borealis and Pentamerus is redefined in the Asker District. The occurrence of Eocoelia
in the Skien District is recorded for the first time. Most of the biostratigraphic changes in correlation
involve the Rytteråker Formation.