1. The life cycle of Austrobilharzia terrigalensis Johnston, 1917 is described. The larval stages occur in Pyrazus australis, a common mollusc on sand flats of estuaries and coastal lagoons in New South Wales.
2. Austrobilharzia terrigalensis was originally described from the seagull, Larus novae-hollandiae. Experimental infections have been successful in young gulls of this species and in the budgerigar Melopsittacus undulatus and the pigeon Columba livia.
3. Under experimental conditions the cercariae will cause dermatitis, and cases of dermatitis resembling cercarial dermatitis have been reported after bathing in Narrabeen Lagoon, where about 4 % of Pyrazus australis carry forktail cercariae.
4. The cercaria was described previously (Bearup, 1955) as Cercaria variglandis subspecies pyrazi, new subspecies. Now that the adult form has been identified as a previously described species the subspecific name pyrazi lapses.