| Summary: | Antarctic sponges have been studied since the 19th Century and are relatively well known compared to other world faunas (Calcinai & Pansini, 2000). Moreover, due to the peculiar characteristics of the Antarctic environment, their spatial distribution is certainly more homogeneous than for faunas at lower latitudes (Sara` et al., 1992). A total of 33 Demosponge species, already known for the Ross Sea, were identified and reported in this article, with an additional two species described here as new. Two new species of Poecilosclerida Crella (Crella) aurantiaca sp. nov. (Crellidae) and Mycale (Aegogropila) denticulata sp. nov. (Mycalidae) are described on the basis of material collected during the XX Italian Expedition (2004–2005) in Antarctica. Crella (Crella) aurantiaca sp. nov. is based on presence of acanthostyles of two size-categories. Mycale (Aegogropila) denticulata sp. nov. is characterized by the presence of palmate anisochelae and styles. The first new species is assigned to both genus and subgenus Crella due to the presence of true echinating acanthostyles, a tangential ectosomal crust of acanthoxeas and to the absence of chelae. However, its peculiar and unusual characteristic is the presence of acanthostyles together with tornotes in the deeper choanosomal tracts. The second new species, according to the characteristics of the ectosomal skeleton, is assigned to genus Mycale and to the subgenus Aegogropila. Mycale (Aegogropila) denticulata sp. nov. is characterized by anisochelae in a single size-category as the only microscleres present.
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