There is a ctenidium, except in some Thecosomata and Gymnosomata, and an osphradium. |
Without shell and operculum, but with pallial cavity and ctenidium. |
The ctenidium is bipectinate with a short afferent membrane and thus the free portion is long. |
To the left of the ctenidium a pulmonary sac, separated from it by an incomplete septum, amphibious. |