This is one of the most common serpulids in Norway. It belongs to the family Serpulidae, which are identifiable by their calcareous tubes. Hydroides norvegica is found in shallow waters attached to hard substrates or to other organisms. In Norwegian ports, this species is found on artificial surfaces or growing on other organisms such as kelp holdfasts, sometimes in high densities. 

Hvitrørmark Hydroides norvegica Gunnerus, 1768
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Kart. Utbredelse i Norge.