Active animal is egg-shape with a large flat foot, and tentacles on a snoutless head, but no external gills or siphon.
Very weakly calcified, amber-brown shell consists mainly of periostracum (see fig. 34) which, when live, forms a velvety surface often mistaken for the mantle of Lamellaria or a dorid seaslug. Length c. 15 mm. Mull, Scotland, March 2015. © G.Brown.