Prosthiostomoidea is a superfamily of flatworms. There are 78 species of Prosthiostomoidea, in 6 genera and 1 family. It includes groups like Prosthiostomidae. They rely on ciliary gliding to move around.
Definition: Eye-spots which may be set into a pit to reduce the angles of light that enters, to allow the organism to deduce the angle of incoming light. Lens-like structures may be present, but stemmata, unlike lens eyes, cannot form an image, either for lack of refractive power or retinal resolution.