The marginal eyespots are difficult to see in living specimens but the gut can be discerned through the skin and has the branching form typical of this order of flatworms.

The upper surface is tan with a few darker brown streaks and spots while the underside is paler and largely unspotted.

It is found on the lower shore and in the shallow sub-littoral zone, under rocks, on pilings, on the fouled hulls of boats and among mussels and rock-boring bivalves.

[2] In Washington State, breeding takes place in March, and in the laboratory, this flatworm has bred between June and August and in December.

About 150 are laid, and are packed closely in one or two layers, forming an egg plate that is stuck to a rock surface.