In this contribution a new representative of the taxon Meidiama Marcus, 1946, Meidiama uruguayensis sp. nov., from Uruguay, is described, as are six more new species, for which three new genera are proposed: Dreuxiola philippi gen. nov. sp. nov., from the French subantarctic archipelago Kerguelen; Yorknia aprostatica gen. nov. sp. nov.; Serrula byronensis gen. nov. sp. nov.; Serrula maxillaria sp. nov.; Serrula concharum sp. nov.; and Serrula acuta sp. nov., from eastern Australia and Tasmania. Arguments are presented to propose a new taxon to contain these new species, rather than include them in the Archimonocelididae Meixner, 1938 (of which Meidiama has been considered a member so far), as well as to remove the Calviriinae Martens & Curini-Galletti from the Archimonocelididae to become a separate taxon Calviriidae. Possible autapomorphies for the three families are discussed. It is also concluded that, with the present state of our knowledge, no sound indications can be given about close relationships.