The Middle Ordovician of the Oslo Region, Norway: 4. Ostracoda

18 paleocop ostracods are described from the Middle Ordovician Ogygiocaris and Chasmops Series of the Oslo Region in Norway. The genus Piretopsis is new, and also the species Ullerella triplicata, U. ventroplicata, Tallinnella trident, T. tumida, T. mjoesensis, T. kiaeri, Ceratopsis? stoermeri, Piretopsis donsi, and Eoleperditia skjesethi. Forms of Tallinnella with swollen features are regarded as examples of neoteny as compared with forms with accentuated relief.