Extreme maximum length 30mm, but in Portugal usually 10mm or less, occasionally 20mm. Elliptical outline, low profile. Ample, soft, translucent, white mantle covers whole body [image 1]; covered in low soft translucent tubercles, inconspicuous unless seen in profile . Irregular line of opaque white tubercles (defensive glands?) around mantle skirt .
Small whitish apex; white stem; and about 7 – 9 lamellae, usually dark chocolate brown, occasionally reddish brown or almost black.
Four to seven plumes, with stout main rib, short stout branches and short pinnae; sparse overall appearance when expanded. Brown, similar shade to rhinophores, apart from medially-white main rib . Able to contract  or retract completely.
Thin, translucent white, almost transparent, with opaque white flecks concentrated at periphery. Concealed when at rest; projects from posterior of mantle when extended in motion . Anterior and sole; no information.
- Low profile, soft, translucent, white body, sometimes tinted yellow.
- Opaque chalk-white or lemon-yellow glands around mantle skirt.
- Rhinophores and gills white.
Portugal to extreme SW tip of England (first record 2012, second 2013), and Mediterranean coast of Spain and France.