"I think this is Phyllidiella nigra, with more isolated tubercles. The clumps are much smaller, and there is no central groups of tubercles as in Phyllidiella pustulosa."
Comment from Nathalie Yonow
I think this is Phyllidiella nigra, with more isolated tubercles. The clumps are much smaller, and there is no central groups of tubercles as in Phyllidiella pustulosa.