The volcano sponge consists of a pale yellow to light green-grey hemispherical head on a conical or umbrella-like expansion that is embedded in the sand.

[2] The conical expansion is smooth and thins towards the circumference, where they form a circular fringed border.

They radiate from a common center in continuation with the lowest spicules of the head, extending downwards into the sand.

[3] Pores mostly occur on the upper part of the head while vents are found in the larger polygonal interspaces at the base.

The fringe of this expansion is formed solely of the forked ends of the longest spicules.