In the event that it is attacked by a starfish, it extends flaps of mantle to defend itself, and the worm also helps drive the predator away.

There is a broad foot which exerts suction on the rock surface, and the mantle is large enough to cover the margin of the shell.

The surface of the shell is sculptured with coarse ribs and is usually greyish-brown or grey, often with dark and pale radiating bands of colour.

[1] The scaled polychaete worm Arctonoe vittata acts as a commensal to D. aspera, living between the foot and the shell.

As a result of these defensive actions, the starfish is unable to get a grip on the limpet shell with its tube feet; it is also possible that there is some chemical deterrent present in the mantle.