It lives in crevices and under rocks, extending its "crown" of branching tentacles into the surrounding water to feed.

It has a cylindrical or spindle-shaped body and an extensible introvert at the tip of which is an elaborate "crown" of branching tentacles.

[3] The body is yellowish-brown to dark brown, the collar (region of the introvert just below the crown) is smooth and blotched with violet, the tentacles are similarly coloured and the pinnules contain specks of purple pigment.

It conceals itself, living in cracks in the rock, under stones and boulders, in clusters of bivalve molluscs and among the rhizomes of Phyllospadix iwatensis.

[2] The breeding behaviour in this species is unusual in that swarming occurs; adult males and females congregate among the rocks forming dense masses before releasing their gametes into the water.