The trilobite genera Panarchaeogonus Öpik, Isbergia Warburg and Cyamops gen. nov. from the Ordovician of Balto-Scandia and British Isles

Panarchaeogonus, hitherto classified with either Olenidae, Brachymetopidae, or Otarionidae [=Aulacopleuridae], is here included in the last-named, and together with lsbergia and Cyamops gen. nov. is placed in the Scharyiinae. Previously known species are described, together with Panarchaeogonus phlyzacius sp. nov. and Cyamops stensioei gen. et sp. nov. Additional species of Panarchaeogonus and Cyamops are described under open nomenclature.