Left: respiratory mantle cavity with opening contained by edge of shell and mantle.
Centre: mantle cut away to expose contents of cavity.
Right: anterior of animal with mantle lobes and shell removed, showing viscera in natural position.
1: substantial, bright orange or brown, bipectinate osphradium which tests the water quality of the inhalent current and, possibly, filters out large debris before the current reaches the ctenidium.
2: large, pale orange or yellow, unipectinate ctenidium with very long filaments.
3: inhalent siphon positioned in front of osphradium. Llŷn Peninsula, Wales, March 2016.