(Χίων), the son of Matris, a noble citizen of Heracleia, on the Pontus, was a disciple of Plato. With the aid of Leon (or Leonides), Euxenon, and other noble youths, he put to death Clearchus, the tyrant of Heracleia. (B. C. 353.) Most of the conspirators were cut down by the tyrant's body-guards upon the spot, others were afterwards taken and put to death with cruel tortures, and the city fell again beneath the worse tyranny of Satyrus, the brother of Clearchus. (Memnon, apud Phot. Cod. 224, pp. 222, 223, ed. Bekker; Just. 16.5.)
[P.S]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