A list is given of the trematode cercariae which are commonly found in the estuarine gastropod, Pyrazus australis Quoy & Gaimard. These include: cercariae of a schistosome, Austrobilharzia terrigalensis Johnston, 1917, and of a heterophyid, Stictodora sp.; a monostomate xiphidiocercaria, probably belonging to the Microphallidae; two megalurous cercariae, probably belonging to the Philophthalmidae; and one echinostome cercaria. The life history of the latter, Acanthoparyphium spinulosum Johnston, 1917, is described. No sporocysts were found. Two generations of rediae precede the cercariae, which have a collar with 23 spines in a single row, as in the adult. Cercariae encyst readily in Salinator fragilis (Lamarck), another gastropod living in the same habitat. Cysts were also found occasionally in P. australis and in small polychaetes of the Phanaerocephala group. Adults were obtained by feeding S. fragilis, which contained encysted cercariae, to the silver gull, Larus novae-hollandiae.