Frustule
Pronunciation : Frus"tule
Part of Speech : n.
Etymology : [L. frustulum, dim. fr. frustum a piece: cf. F. frustule.] (Bot.)
Definition : Defn: The siliceous shell of a diatom. It is composed of two valves, one overlapping the other, like a pill box and its cover.
Source : Webster's Unabridged Dictionary, 1913