- A remarkable genus of marine worms having tentacles around the mouth. It is almost always classed aided by the gephyreans. Its larva (Actinotrocha) goes through a peculiar metamorphosis.
- A genus of Gephyrea, typical associated with the family Phoronidæ.
- [lowercase] A worm regarding the genus Phoronis. See cut at Actinotrocha.