Orsisius

Orsisius (in Greek Arsisios, local name Oresiesis-Heru-sa Ast) was an Egyptian monk and author of the fourth century. His memorial is June 15.
Biography.
He was a disciple of Pachomius on the Island Tabenna in the Nile. When Pacomius died (348), Orsisius was chosen as his successor; but he resigned in favour of Theodore. 
It was not till Theodore's death (c. 380) that Orsisius, advised by St. Athanasius, accepted the abbatial office of hegumen.
Writings.
Theodore and Orsisius are said to have helped Pachomius in the composition of his rule; Gennadius mentions another work:
This is supposed to be the work "Doctrina de institutione monachorum" translated by St. Jerome into Latin Migne prints after it another work attributed to the same author: "De sex cogitationibus sanctorium", which, however, is probably by a later Oresius.