ARSACIDES, Arsacidae, the descendants of Arsaces, King of Parthia. This Arsaces, according to the Persian Chronicles, was of the lineage of Cyrus; though others affirm that he was descended from Darius.—Be this as it will, Arsaces having freed the Parthians from the dominion of the Seleucids, they esteemed him the founder of their monarchy, and would have all their future kings bear his name, and be called Arsacids. Hence the poets have attributed the appellation to the whole nation. The Arsacides began to reign in Arsaces, under Seleucus II. surnamed Callinicus, the third of the Seleucids, 240 years before Christ; and continued about 460 or 470 years; when Artaxerxes killed Artabanus, the last of the Arsacides, about the year of Christ 227.