- The olfactory organ in a few molluscs, linked with the respiration organ. Its primary purpose should test incoming water for silt alongside feasible food particles.
- The olfactory organ of some Mollusca. It's related to the organ of respiration.
- The so-called olfactory organ of mollusks; a patch or region of specifically altered epithelium associated with body-wall in the foot of the ctenidium, given an unique nerve, likely to smell, flavor, or perhaps test water that the pet breathes, thus working as a unique sense-organ.