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Two trilobite taxa, Agnostus (Homagnostus)sp. and Pseudagnostus (PseudagnostuJ) ida!is huskissonensissubsp. nov. are described from the upper part of the Huskisson Group, western Tasmania. The only trilobite previously described from this level is the early Idamean (early Late Cambrian) zone fossil Glyptagnostus reticulatus. Palaeontological and stratigraphic evidence suggests that there may be a disconformity of very late Middle Cambrian age (about Lejopyge laevigata III Zone) within the Huskisson Group, which would correspond to a postulated disconformity of similar age from the Dundas Group at Dundas.

Near Middlesex Road, 9 km northeast of the Hellyer mine, northwestern Tasmania, a mineral exploration hole intersects a polymict volcaniclastic conglomerate of the Southwell Subgroup of the Mt Read Volcanics. At depths of 3 53 m and 364 m, fossiliferous limestone clasrs within this conglomerate contain trilobites, including an unassigned agnostoid cephalon, Amphoton sp., Liopeishania sp., Menocephafites{I) sp., Lisania(?) sp. and an unassigned member of the Dorypygidae, thus suggesting an age of Goniagnostus nathorsti Zone to early Lejopyge Laevigata Zone (i.e. Lare Middle Cambrian) range. This shallow-water fauna is unusual for the Tasmanian Cambrian, in which most faunas are found in deeper water shales and siltstones. The horizon from which the fossils come is strarigraphically close to a rhyolire with a SHRIMP zircon age of 503.2 ±3.8 Ma; the usefulness of this figure in terms of the Cambrian rime-scale is questioned.

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