A selection of early Upper Cambrian trilobites from Queensland is described to lay a basis for zoning of the sequence and to gain knowledge of forms which are, or may become, useful in palaeogeography and in interprovincial correlation. The taxonomy and organization of the same fossils are studied. The zones of the sequence are conveniently grouped in two stages-the Idamean (above) and the Mindyallan (below). The basal Idamean fauna with Olenus ogilviei, and the uppermost with Irvingella tropica, are presented exhaustively. Lesser attention is paid to the Mindyallan fauna, which is rather large and which is studied separately. The paper is written essentially for readers concerned with the stratigraphy, correlation, and palaeontology of the Upper Cambrian of Australia. Some items of a more general interest, however, are also included. These are a discussion of the concepts of zones and stages and their nomenclature, and some problems of organization and suprageneric classification of trilobites. The source of material is the Commonwealth Palaeontological Collection, Bureau of Mineral Resources, Canberra. The fossils from the Glenormiston area were collected by a party of Bureau geologists led by J. N. Casey, and the writer participated in this enterprise. The fossils from the Selwyn Range and Pomegranate Creek area were collected by the writer. The complete specimens of Erixanium illustrated on Plate 9 were collected by Mr R. B. Leslie and party, Frome-Broken Hill Co. Pty Ltd, and kindly released for description by the Management of that Company.
