 Like most in this genus the animal has a large muscular mantle, folds of which can completely cover the whitish shell, giving it a slug-like appearance.In "S. breviculus" the colour is a glossy dark almost jet black, as are the thick tentacles and snout.These inhabitants of the sub-littoral fringe shun light, clinging to the undersides of large rocks and boulders in a wide range of habitats, usually down to a depth of 20 metres.