👉 Mastigostyla is a group of organisms that live in the order Gastropoda, which includes echinoderms, bivalves, and gastropods. These animals are characterized by their long, slender bodies, with a single pair of arms (masts) attached to the sides of the body. Mastigostylas typically have an internal cavity or organ that contains many small, distinct structures called 'organs' or 'spines'.