The generic characters, taxonomic positions, and geographical distributions of the genera Leolasma Kaljo 1956 and Ullernelasma n.gen. are discussed, and three new species are described, viz. Leolasma pachycolumnaris n.sp. from Middle Ordovician (Viruan) Macrourus Beds, Öland, Sweden, Streptelasma unicum n.sp. from uppermost Ordovician (Harjuan) or lowermost Llandoverian beds, Östergötland, Sweden, and Ullernelasma svartoeyensis n.sp. from the Upper Ordovician (Harjuan) stage 5b of the Oslo Region, Norway.