The trilobites Mitroplax gen. nov. and Spiniscutellum (Scutelluidae) from the Lower Devonian of Victoria, Australia

The new scutelluid trilobite genus Mitroplax , with type species M. enormis (Etheridge, 1894), occurs in Pragian to early Emsian strata at several localities in Victoria, Australia. The genus is characterized by a remarkably long and flat anterior cephalic border, a glabella that expands almost uniformly forward from the occipital furrow, a subcircular S2 discrete from S1, and a pygidium with the well-rounded paired pleural ribs and the posterior bifurcations of the postaxial rib tapering almost to a point distally. The type species grew to exceptional size, as indicated by the dimensions of the largest pygidia. Another scutelluid from the Lochkovian of Victoria, ‘ Goldius ’ greenii Chapman, 1914, is revised and assigned to Spiniscutellum Šnajdr, 1960. This species and a related one from the Lochkovian of the Bungonia district of south-eastern New South Wales are the first records of Spiniscutellum from eastern Gondwana. Spiniscutellum ( Lochkovopeltis ) Hörbinger, 2004 is regarded as a junior synonym of Spiniscutellum . •