The following is taken from Fr. Thomas Walsh's History of the Irish Hierarchy at p. 308:
[The See of Clonfert] was founded about the year 550. Some are of opinion that Saint Brendan was the first bishop because Saint Moena is called his successor in the calendar of Cashel but St. Brendan's establishment having become so extensive that a bishop was necessary to ordain missionaries and assist the founder, St. Brendan, in its government, Saint Moena, it seems, was the person who was chosen by Brendan on this occasion and who afterwards founded the see of Clonfert. In its cathedral were seven altars. There is much confusion in the accounts relative to St. Moena it is probable that he was a native of Britanny and came to Ireland with St. Brendan on his return from that country. Moena's death is noted on the 1st of March A.D. 571.
