Sea lilies belong to a larger group of animals called the echinoderms (i-KIE-nuh-durms), which also includes sea urchins and starfish. All these creatures have a system of tubes operated by water pressure. Sea lilies use the system to catch food. The tubes extend along the branches of the arms and end in tiny, movable tube feet. These produce mucus to trap food particles and also flick tiny organisms into grooves in the arms. The grooves then convey food toward the upward-facing mouth.