Brachiopods of theMarginirugus barringtonensisandLevispustula levisZones comprise the youngest of three major Carboniferous biostratigraphic units in eastern Australia. The remarkable change in the composition of marine invertebrates between the second and third of these units, a transition that only two brachiopod species are known to survive, has been attributed to the isolation of eastern Australia and to a drop in temperature. TheMarginirugus barringtonensisandLevipustula levisZones are redefined from reference sections in the Myall region, N.S.W.; theL. levisZone now includes theSyringothyris bifidaZone of Campbell (1961). Faunal sequences show that these two zones are closely related and that there is no hiatus between them, as formerly proposed by McKellar (1965). Conodonts identified by Mr. D. Crane indicate a late Viséan to early Namurian age for theMarginirugus barringtonensisZone, and an age of early Namurian for the base of theLevipustula levisZone; brachiopod evidence indicates that theL. levis Zoneextends into the Westphalian. The youngerAuriculispina levisZone from the Yarrol Basin may be coeval with theTrigonotreta campbelliZone from N.S.W. Faunas from both theL. levisandA. levisZones are present in Argentina and many species from theL. levisZone have affinities with forms from the Baikal region, U.S.S.R. Correlations based on the zones have eliminated the need for a hiatus between the Branch Creek and Baywulla Formations in the Yarrol Basin.