Saint Mungo and Saint Columba
There is a tradition that Saint Mungo and Saint Columba met and exchanged pastoral staffs as a sign of respect for the work which each was doing for Christ in different parts of Scotland, recognising the jurisdiction of each for different areas. Saint Columba was an abbot, never a bishop, but these were early days when that sort of thing was still being worked out. Curiously perhaps to us, there always was a member of Saint Columba’s community who was a bishop, who was needed to ordain priests. The bishop was subordinate to the abbot, but Saint Columba always gave preference to the bishop in the celebration of Mass.