Note: The species is up to a few cm long and grows in the upper subtidal and lower part of the intertidal. It is often an epiphyte on Cladophora rupestris. In southern Norway it is found during spring, while it may also be found during summer in northern Norway. The thallus is pluriseriate in older parts, otherwise the axes are uniseriate. It has conspicuous main axes with side branches normally opposite or in whorls. Unilocular sporangia often occur together with the whorl branches, or opposite a side branch.