It has a bubbly-looking appearance with internal channels visible through the surface and large, raised oscules.

The consistency is fairly soft and elastic but the surface feels crisp because of the vertical spicule bundles supporting it.

In these areas, it is usually found between low-water mark and a depth of 400 metres (1,300 ft) on vertical rocks and sites with clean water exposed to strong tidal flows.

[3] It also occurs in the north Pacific Ocean from Japan to California, where it is often found growing on the shells of scallops in the genus Chlamys.

M. incrustans is viviparous and in the months of August and September, developing embryos are sometimes found inside the tissues.