Chemical analysis of southern Australian marine sponges of the genera Higginsia and Spongosorites has yielded examples of the discorhabdin class of alkaloids. These include the known metabolites (+)-discorhabdin A (1), (+)-discorhabdin D (2), makaluvamine J (6), and damirone A (7), together with four new analogues, (+)-dihydrodiscorhabdin A (3), (+)-debromodiscorhabdin A (4), (+)-dihydrodiscorhabdin L (8), and (+)-discorhabdin X (5), with the latter compound being the first reported example of a thio heterocycle flanked by oxo-thio-acetal and azo-thio-acetal functionalities. Structures for the new compounds were assigned on the basis of detailed spectroscopic interpretation.