Pseudoceros flatworms are part of the phylum Platyhelminthes. Their bodies are shaped like an oval and have a velvety surface, a grey-black ventral side and short pseudo tentacles formed by folds of the forward margin. They normally live in the tropical oceans around the world and are one of the largest species of flatworms. They have the same muscular system as most flatworms that involve flame cells and flagella used for locomotion and muscles that attach themselves to collagen fibers instead of a skeleton.