nOsphradium(Zoöl) The olfactory organ of some Mollusca. It is connected with the organ of respiration.
Century Dictionary and Cyclopedia
nosphradiumThe so-called olfactory organ of mollusks; a patch or tract of specially modified epithelium of the body-wall at the base of the ctenidium, supplied with a special nerve, supposed to smell, taste, or otherwise test the water which the animal breathes, thus functioning as a special sense-organ.
Webster's Revised Unabridged Dictionary
NL., fr. Gr. strong scent, fr. to smell
There is a single well-developed, often pectinated osphradium.
"Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 5" by Various