Similar though less organized organs were reported from the body cavity of the asteroid Archaster typicus . Urns of A. typicus are located along the lateral wall of the arms, predominately near the gonads in the vicinity of the serial gonoducts, where they form clusters. Urnal cavities are heavily ciliated and most of them are occupied by clots of coelomocytes that seem to be unattached to urnal cells. Ciliated urns could produce steady water currents through the urnal cavity. The material conveyed by the coelomic fluid enters the urnal cavity and is either trapped by coelomocyte pseudopodia or agglutinated by a mucoid substance produced by mucous cells located close to the urnal aperture.
Ciliated urns appear to be involved in the clearance of the coelomic fluid.