The family Beyrichiidae is discussed and divided into 4 subfamilies; Beyrichiinae, Kloedeniinae, Zygobolbinae, and Treposellinae subfam.n. A new genus, Cornikloedenia, and 5 new subgenera of Beyrichia (Eobeyrichia, Neobeyrichia, Nodibeyrichia, Vehbeyrichia, and Mitrobeyrichia) are erected. 26 beyrichiacean ostracods from the Silurian of the Oslo region are described. A chart (p. 67) shows their stratigraphical and geographical distribution. The genus Signetopsis is new, and the following species and subspecies are also new: Beyrichia paucituberculata, B. zygophora, B. osloensis, B. skienensis, B _ kiaeri, B. ringerihensis, Craspedobolbina arrnata, C. dorsoplicata, C. expansinodata, Platybolbina tiara densistriata, P. lunulifera, P.? bulbosa, Prirnitiella? bipunctata, Primitiopsis dorsoplicata, Signetopsis quadrilobata, and S. rnalornata.