English: Tube-dwelling anemones; Ceriantharians.
Ceriantharia look very similar to sea anemones but belong to an entirely different subclass of anthozoans. They are solitary, living buried in soft sediments. Tube anemones live inside and can withdraw into tubes, which are composed of a fibrous material made from secreted mucus and threads of nematocyst-like organelles known as ptychocysts. Within the tubes of these ceriantharians, more than one polyp is present, which is an exceptional trait because species that create tube systems usually contain only one polyp per tube.
Ceriantharia were formerly classified in the taxon Ceriantipatharia along with the black corals, but have since been moved to their own subclass, Ceriantharia.