is a large, round sea slug up to 12 cm in length. The body consists of the brown mantle, which is covered in short fleshy projections known as tubercles, and a white foot, which forms a 'skirt' around the mantle. The front end bears obvious tentacles the outer oral tentacles and the rhinophores between them. The rhinophores consist of rolled extensions of tissue.Pleurobranchus membranaceus
may be seen swimming by turning onto its back and flapping the foot like wings.