Webster’s Revised Unabridged Dictionary · 1913
Rostellum
Ros·tel′lum (·lŭm), n.; pl. Rostella (#). [L. See Rostel.] A small beaklike process or extension of some part; a small rostrum; as, the rostellum of the stigma of violets, or of the operculum of many mosses; the rostellum on the head of a tapeworm.