Ptolemy III Euergetes
He ruled for ten, nineteen or thirty years, depending on the source consulted, and took vengeance on Cobthach's children, before being killed by Cobthach's son Meilge Molbthach. The "Lebor Gabála" dates Cobthach's death and Labraid's accession to Christmas Eve, 307 BC, and also synchronises his reign to that of Ptolemy III Euergetes (246–222 BC). The chronology of Keating's "Foras Feasa ar Éirinn" dates his reign to 379–369 BC, the "Annals of the Four Masters" to 542–523 BC.