The taxonomic study reported in this paper concerns tropical Australian marine sponges assigned to the order Haplosclerida. Morphological characters of species from three families are described: the Chalinidae (Haliclonci amhoinensis (Levi), H. cymifomiis (Esper), and Cladocroce aculeata Pulitzer-Finali), Niphatidac (Niphates nitida n. sp., Amphimedon paraviridis n. sp., A. Uimellaui n. sp., A. terpenensis n. sp., A. sulcata n. sp., Gelliodes fihulata (Carter), Aka mucosa (Bergquist), and A.

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... atypica n. sp.) and Callyspongiidae (Cally.spongia muricina (Lamarck), C. aerizusa Desqueyroux-Faundez, and C. pseudoreliculala Desqueyroux-Faundez). Of the four¬ teen species studied, six are described as new to science, and four are new species records for the region. Taxonomic problems addressed in this study include the difficulty with the ordinal and family location of the group of coral-boring sponges comprising the genus Aka de Laubenfels. 1936, and the few character states found to distinguish the clo.sely related genera Niphates Duchassaing and Michclotti, 1864, and Amphimedon Duchassaing and Michelotti, 1864. The diagnoses of the genera Haliclona Grant, 1835, and Callyspongia Duchassaing and Michelotti, 1864, are modified as a result of a review of the literature and additional features recognised in this study.