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. At night they move around to feed, usually browsing on various alga such as "Hormosira", or "Ulva" sp. in estuaries and harbours, often returning to the same bare scar in the rock in which they spent the previous day. This is sometimes referred to as 'homing behaviour'.