Dictionary entry

Sphæridium

Webster's Dictionary 1913

‖Sphæ‐rid″i‐um (?), n.; pl.Sphæridia (#). (Zoöl.) A peculiar sense organ found upon the exterior of most kinds of sea urchins, and consisting of an oval or sherical head surmounting a short pedicel. It is generally supposed to be an olfactory organ.