Starfish, member of a class, Asteroidea, of star-shaped marine echinoderms, with 5-fold symmetry. A starfish consists of a central disk surrounded by 5 or more radiating arms. There is a dermal skeleton of calcite plates, and a water-vascular system gives rise to rows of tube feet on the lower surface by which the animal moves about. The mouth is on the lower surface. Most species are carnivorous or omnivorous scavengers. Starfishes can regenerate lost or damaged parts.