Lewis & Short

Syrĭarcha, ae, m., = Συριάρχης, the chief priest in Syria, Cod. Th. 15, 9, 2; called Syrĭarchus, Just. Nov. 89, 15.
His office is called Syrĭarchĭa, ae, f., = Συριαρχία, Cod. Th. 12, 1, 103.