Crinoids (sea lilies) are marine animals that make up the class Crinoidea of the echinoderms (phylum Echinodermata). They live both in shallow water and in depths as great as 20,000 feet. Sea lilies refer to the crinoids which, in their adult form, are attached to the sea bottom by a stalk. Feather stars or comatulids refer to the un-stalked forms. Crinoids feed by filtering small particles of food from the sea water with their feather like arms. Undated, no illustrator credited.