The Osphradium is the olfactory organ in certain molluscs, linked with the respiration organ. Classes Caudofoveata Aplacophora Polyplacophora - Chitons Monoplacophora Bivalvia - Bivalves Scaphopoda - Tusk shells Gastropoda - Snails and Slugs Cephalopoda - Squids, Octopuses, etc. ... Respiration can refer to: Cellular respiration, which is the use of oxygen in the metabolism of organic molecules. ...