Polyclad flatworms of the are marine, free-living flatworms known for their thin, flexible bodies and often striking coloration. The body is typically broad and oval to elongate, strongly flattened, and lacks any hard structures, allowing the animal to glide smoothly over substrates. Many species display vivid colour patterns. The dorsal surface is usually smooth, while the ventral side carries a ciliated epidermis that enables locomotion by gliding. Polyclads have a highly branched digestive system and a ventral, protrusible pharynx, which they use to feed on small invertebrates such as ascidians, mollusks, or crustaceans. Pericelis flatworms are commonly found in shallow tropical and subtropical marine habitats, especially on coral reefs, rocky substrates, and under stones, where they remain hidden during the day and become more active at night.