Confidence: It's likely to be this, but I can't be certain.
Notes: because of the growth pattern this is more likely to be M.membranacea. E.pilosa grows erratically very often star shaped clusters. Did you look at the sea-mat with hand lens this would give it away. E.pilosa has conspicuous spines which don't look apparent here. M.membranacea has blunt bristles on each side of rectangular zooids.