osphradium
noun
os·phra·di·um
plural osphradia
-ēə
: a single or paired sense organ connected with one of the visceral ganglia and situated near the gill of most aquatic mollusks that is supposed to be olfactory or to test the purity of the water passing to the gills
Word History
Etymology
New Latin, from Middle Greek osphradion nosegay, diminutive of Late Greek osphra smell; akin to Greek ozein to smell