[1] Its tentacular crown is formed of several, fused, horseshoe-shaped tentacle lamellae.

The second segment has two body folds, near which open the genital ducts.

The trunk, which comprises 89% of its total body length, is undifferentiated.

The heart is a simple muscular elaboration of the anterior end of the ventral blood vessel.

The brain is large, and from it arises a pair of intraepidermal nerve cords, which extend the full length of the vestimental region; thereafter, they join and form the a nerve cord of the trunk.