Four new demosponge species from Terra Nova Bay (Ross Sea, Antarctica)

Four new demosponge species: Iophon terranovae n. sp. (Iophonidae), Ectyodoryx minuta n. sp. (Coelosphaeridae), Microxina lanceolata n. sp. and Microxina sarai n. sp. (Niphatidae) are described on the basis of material collected during several Italian Antarctic expeditions. Iophon terranovae is based on the presence of large mucronate-oxeote-styles and on the absence of true acanthostyles. Ectyodoryx minuta is a bushy amorphous species based on the small size of the megascleres, the peculiar shape of the anisotornotes and the presence of two categories of anisochelae. The two other new species are assigned to Microxina Topsent, 1916, a genus that recently received Hemigellius Burton, 1932 as synonym. Microxina lanceolata is a branched species characterized by the lanceolate extremities of the oxeas, whereas M. sarai is massive lobate and has a thin ectosomal membrane with tangential oxeas (a character that is not shared by the other species in this genus).