学名:Noumea decussata Risbec, 1928
Mantle white, sometimes with obscure yellow specks. Rhinophore clubs are red and the translucent clear gills have a red line along the inside edge. The mantle has pair of folds about two-thirds of the way down the body, given it a cross-like or cruciform appearance. There has been some confusion between this species and Noumea simplex in the literature, some of it no doubt due to Risbec (1953) misidentifying specimens of Noumea simplex as N. decussata. In Noumea simplex the mantle ranges in colour from pink to white and there is usually an orange-red line, often broken, along the edge of the mantle, and the tips of the gills and rhinophore clubs are bright orange. Compare also with Noumea romeri which also has a pinkish mantle. In that species there is a distinct whitish border to the mantle, the outer edge of the vibratile gills is orange and the upper half of the rhinophore clubs are orange.
See Scott Johnson’s observations of N. decussata feeding on a yellow species of aplysillid sponge, and Carol Buchanan’s photo here of it on another aplysillid. Both sponges seem different from the bright pink aplysillid sponge which N. simplex and N. romeri are usually associated with.