The material of this article was kindly furnished by Miss Elizabeth Pope, Curator of Worms and Echinoderms, the Australian Museum, Sydney, who was assisted in collecting by Misses P. McDonald, F. Wilson and B. Dew, and by Mr. Ederic Slater, who also took a series of kodachromes, which have been of great aid in establishing the colour in nature. Miss Pope also sent valuable notes and colour sketches. All the specimens were collected in the intertidal zone at Long Reef, near Collaroy, north of Sydney, New South Wales, during the summers of 1955 and 1956. The material comprised 30 specimens, belonging to 10 species, of which three are identical with species in Haswell's (1907) report; the remainder are considered new. Extensive definitions of families and genera appear in my 1953 monograph but are repeated here for the benefit of Australian zoologists. Unfortunately, acotylean polyclads cannot be identified except by means of serial sections of the copulatory apparatus. Cotylean polyclads may often be identified by the colour pattern. The eye arrangement can be made out accurately only in dehydrated, cleared specimens. Field identification is generally impossible except in the case of species with striking colour patterns.