Two host-specific, extremely cryptic, small dendronotoid nudibranchs from Australia are described and classified, and their phylogenetic position within the superfamily is discussed. Lomanotus vermiformis Eliot, 1908 subsists exclusively on the hydrozoan Lytocarpus philippinus (Kirchenpauer, 1872). Lomanotus stauberi Clark & Goetzfried, 1976 is newly synonymized with L. vermiformis. Marioniopsis platyctenea sp. nov. subsists exclusively on the alcyonacean Parerythropodium hicksoni Utinomi, 1972. Marianina rosea (Pruvot-Fol, 1930) is relocated to the Tritoniidae (wherein it forms a monotypic subfamily, Marianinae) because of possession of palmate rhinophoral clavi, the principal apomorphy of the Tritoniidae. The validity of using the form of the digestive gland as a basis for dividing the Tritoniidae is questioned since it is acknowledge that this organ has progressed from a solid (holohepatic) arrangement to a dispersed (cladohepatic) arrangements in parallel in several major nudibranch lineages; form thus offers merely homoeoplaseous phylogenetic characters. Separation of right and left digestive glands appears to be one of the first steps in the simultaneous and interdependent evolutionary processes of internal detorism and external 'aeolidization' in nudibranchs.Descriptors: LYTOCARPUS PHILIPPINUS