Diagnosis: Bioclaustration structure in bryozoans, consisting of a group of pits sunk into the surface of zoarium. Pits c. 2 mm diameter, up to c. 2 mm deep; in plain view pit mouth subcircular to oval with slightly to strongly fluted edges; pit walls may extend up above bryozoan surface to form low thickened rim around pit mouth. mature specomens consist of arrays of up yo thirty or more such pits; in centre af array, pits spacd evenly, c 2-3 mm apart; towards periphery, pits lie equispaced along strait or gently curving lines, each often terminating in a groove, c 2 mmwide, several millimetres long; groove shallows diatally so that outer end merges imperceptibly with surface of surrounding zoariu. Floors of adjacent pits along line joined by tunnels, c 2mm wide, 0,5 mm high. Lines increase in number by bifurcation.