The Litho - Lithophyllon undulatum - is a little more rare in this hobby. These LPS corals are very slow growers, and are recognized by the grouping of its mouths that are aligned in rows. They don't show up often; sellers don't usually carry them. I've had mine for about five years and it has tripled in size in that time. It's dead center in my reef, about 6" off the sandbed near a Sunset montipora colony because they contrast so nicely.