Clathrina clathrus
Clathrina clathrus is a species of calcareous sponge belonging to the family Clathrinidae.
This yellow sponge, up to 10 cm in diameter, usually appears cushion-shaped at a distance. Close-up the sponge can be seen to consist of a tangled mass of tubes. Like C. coriacea, the spicules are exclusively three-pointed triactines.
This is a shallow-water species found in the Mediterranean and on Atlantic coasts of Europe as far north as the British Isles.