Ascandra contorta

Ascandra contorta is a species of calcareous sponge belonging to the family Clathrinidae.
This is a whitish sponge which appears as a mass of irregular, convoluted tubes. It is very similar to "Clathrina clathrus" but usually differs in colour ("C. clathrus" is usually yellow) and by the presence of terminal oscula on vertical tubes (absent in "C. clathrus"). When viewed microscopically, the spicule structure of the two species is very different, "A. contorta" possessing two-pointed "diactines" and four-pointed "tetractines" as well as the three-pointed "triactines" which "C. clathrus" is exclusively made up of.
This sponge is found on north-eastern Atlantic coasts from the Arctic to the Mediterranean, usually on rocks at depths of 10–30 m, but occasionally in shallower water.