Barrel Sponge

Persistently a cup- or barrel-shaped sponge with a rough, often jagged, stone-hard exterior. Giant specimens may reach a diameter of up to 2 meters. These specimens may be over 100 years old, as the sponges grow only about 1.5 cm a year. Smaller specimens may assume a cone shaped form, i.e. with the base broader than the top. Walls on the outside irregularly ridged and pitted (X. muta-close-up). In between the elevations, the surface is smooth. Mostly without oscules, but there may be a few small openings (2-3 mm in diameter) which appears to be oscules. Inner wall rough, irregularly conulose. Wall up to 2.5 cm thick at the top, thicker halfway down. The central cavity extends to about half way the height of the cup. The consistency is brittle, incompressible and easily to crumble or break.