Didiscus gladius sp. nov. is described from Bahia State (Brazil). The sponge is thinly encrusting to lump-shaped and has a glassy, translucent appearance, through which the spiculation is clearly visible. The megascleres are styles and two categories of oxeas. The microscleres are discorhabds. Colour is beige or brown in ethanol. Didiscus verdensis is the nearest relative in the Atlantic which differs from the new species in a series of traits (e.g. absence of true styles and presence of strongyles). A key to species of Didiscus is given.
