Deflated specimen. Propodium folded into an inhalant respiratory siphon (1).  Cephalic tentacle (2). Posterior edge of propodium (3). Rib connecting bases of tentacles (4). Single, subsutural, spiral line of purplish marks on body whorl hidden by periostracum remnants. Colours are strongest on live specimens in water. Shell height 26 mm. Sublittoral, Llŷn Peninsula, Wales. September, 2015. Leg. P. Brazier.