A heterogeneous group of animals is consistently if variously associated with the infralittoral maerl of the eastern North Atlantic. The findings of this study conform to the general pattern. 6 types of maerl substrate have been arbitrarily distinguished for the area of the investigation. In each case, Lithothamnium corabllioides var corallioides constitutes the bulk of the deposit. The associated macrobenthic animals were quantitatively investigated, using in situ sampling techniques. Particular attention is accorded to the anomalous occurrence of high-density populations of Paracentrotus lividus and mixed aggregations of Antedon bifida and Ophiocomina nigra.