The butterfly blenny has a deep body at the front, tapering rather quickly to the caudal peduncle.

It has tentacles on the nasal opening, above the eye and on the nape near the first dorsal fin ray.

There is a large bluish-black eyespot surrounded by a white ring on the 6th and 7th rays of the dorsal fin.

It is found over rocky substrates covered with seaweed and this means that it is seldom caught in trawls, and may be more common than it seems.

[5] An individual near Plymouth was found to be nesting inside the cavity of a large thigh bone.