daughter of Gelon, the son of Hieron II., king of Syracuse. She was married to a Syracusan named Themistus, who, after the death of Hieronymus (B. C. 215) was elected one of the captains-general of the republic; but these being soon overthrown by a fresh revolution, in which Themistus perished, a decree was passed condemning to death all surviving members of the family of Hieron; and, in pursuance of this barbarous resolution, Harmonia was immediately put to death, together with Demarata and Heraclea, the daughters of Hieron. (Liv. 24.24, 25; V. Max. 3.2. ext. § 9.)
[E.H.B]A Dictionary of Greek and Roman biography and mythology
Smith, William
A Dictionary of Greek and Roman biography and mythology. William Smith, LLD, ed. 1890