Eurypon simplex (Bowerbank, 1874) is a thinly encrusting hispid sponge. It is known from several localities off the coasts of Europe, but invariably from deeper water.
Colour: Whitish in alcohol, pale yellow in dried condition, possibly red alive.
Shape, size, surface and consistency: Thin encrustation on shells, stones and pebbles, up to 0.4 mm in thickness. Surface hispid due to projecting spicules. Meandering subdermal canals visible, but no apparent oscules.
Spicules: Tylostyles, very stout and long, with prominent heads, with often a ring swelling just beneath it: up to at least 3600 x 43 µm; some of the tylostyles are deformed into shorter "tylotes"; styles, often arranged in bundles of 3-6, smooth: 480 x 3-4 µm; acanthostyles, entirely spined: 108-180 x 8-10 µm.
Skeleton: Long tylostyles are erect on the substrate, points outward, protruding beyond the ectosome; bundles of slim styles scattered throughout the sponge.
Ecology: On pebbles, at 60-260 m.
Distribution: Roscoff, Faroes.
Type specimen information: The type is in the Natural History Museum, London.
Eurypon lacazei shares the extremely long tylostyles with the present species, but they differ in the form of the auxiliary spicules: smooth oxeas in E. lacazei, smooth styles in E. simplex.
Source: Brøndsted, 1932.