Iolaea eucosmia is a species of sea snail, a marine gastropod mollusk in the family Pyramidellidae, the pyrams and their allies.

The whorls of the protoconch are deeply obliquely immersed in the first of the succeeding: turns, above which only the tilted edge of the last one project.

The six whorls of the teleoconch are somewhat contracted at the periphery and very strongly slopingly shouldered at the summit.

The outer lip is rendered angulated by the keels, thus showing the external sculpture within.

The columella is slender, very strongly curved, slightly reflected and provided with a weak fold at its insertion.