Steromphala cineraria feeding opportunistically on the soft interior of a Laminaria stipe exposed by the stronger radulae of Lacuna vincta or, perhaps, originally by Patella pellucida.
The white fringed left neck lobe is visible by the tentacle. It is positioned to allow clean respiratory water to enter above it to the ctenidium (gill) within the mantle cavity, and to restrain food particles below it so they do not contaminate the ctenidium.