Mantle recently sloughed.
Occasionally, some internal organs are partially visible through the translucent thin mantle and shell of live, recently sloughed specimens.
The shape of the shell and its protruding spire (1) can be detected on this live specimen by the yellowish viscera covered by it.
Also visible are the bright-brown, bipectinate osphradium (2) that tests the water quality of the inhalent current and, possibly, filters out large debris before the current reaches the ctenidium, and (3) the rim of internal shell.
Image on right taken sublittorally c. 12m depth. Moray Coast, N.E. Scotland. May 2018. Leg. & © C. Rickard.