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Seventy-eight species of Ascidiacea, including 21 new species from deeper waters (about 100 m and occasionally to about 500 m) off Western Australia appear to represent a diverse fauna not previously sampled. The relatively few solitary species taken include two possibly introduced (Styela plicata and S. clava). Large aplousobranch colonies dominate the collections. Aplousobranch species with numerous, small, deeply embedded zooids in massive three-dimensional, vertical and often branched or stalked inflexible colonies supported by embedded sand (Polyclinindae) or calcareous spicules (Didemnidae) are common. Species with flexible stalks (enabling them to respond to prevailing currents) such as Clavelina meridionalis, Sigillina australis and S. cyanea were not taken often. Some known species (e.g. Synoicum chrysanthemum, and Atriolum tubiporum) previously considered rare were taken at these depths in significant numbers. Other unusual taxa (Pseudodiazona longigona and Condominium spp.) are recorded from new locations but do not appear to be common. [ABSTRACT FROM AUTHOR]

Three colonial aplousobranch ascidian species from the central coast of New South Wales were originally described from one of the earliest significant regional collections of Australian ascidians (Herdman, 1899). They have a similar habit, their colonies being long, oval to cylindrical gelatinous heads on relatively short, thick, fleshy stalks and they all respond in the same way to the multidirectional currents to which they are subjected in the habitats they occupy. Nevertheless, they are not closely related phylogenetically. One is the monotypic Euclavella claviformis (Herdman, 1899), known only from the central eastern Australian coast and the North Island (New Zealand). The second species is the indigenous Hypsistozoa distomoides (Herdman, 1899), known from the Great Australian Bight and the central eastern coast of Australia but related closely to the only other species known in this genus, its type species H. fasmeriana (Michaelsen, 1924), known only from New Zealand. The third species discussed, Sigillina cyanea (Herdman, 1899), an indigenous Australian species known from a wide range around the Australian continent, has no closely related species in the indigenous New Zealand fauna although a similar and partly sympatric species Sigillina australis (Savigny, 1816) does occur in New Zealand. A close relationship of Sigillina to the Pseudodistomidae (rather than the Holozoidae) is apparent. Larvae of H. distomoides are found to have characters formerly known only in larvae of the type species (see Brewin 1956, 1959). [ABSTRACT FROM AUTHOR]