Since Eugene’s episcopal appointment was not to be as a bishop in charge of a diocese, he was given a titular diocese (that no longer existed) – Icosia. He explains to Father Tempier.
If you have an interest in Icosia, put this in your notebook; it is in Africa, as I told you; your friend’s mission is for Tripoli, with Tunis added on. The sensitivity of the French Government is no doubt the reason for not including Algiers.
Letter to Henri Tempier, 1 October 1832, EO VIII n 435
If you knew what Icosia is, your heart would beat a little faster. Its origins go back to the time of the fables; it is claimed that it was built by Hercules’ twelve companions who settled there at the time of the famous expedition to horizons “nec plus ultra”, in other words to Gibraltar. Its Greek name means: twenty. What is more certain is that it was the episcopal city in the heyday of the African Church and that Laurentius, its bishop, took part in the Council of Carthage held in 419, as legate of Mauretania Caesariensis, its province: “Laurentius Icositanus, Legatus Mauritaniae Caesariensis”, which serves to fix pretty well its location, and – pay careful attention, Father Hardouin claims that it is today’s Algiers. For my own part too I do not question it any more than he, and you will doubtless follow my opinion. I shall not fail to point it out to the Holy Father, on the day I go to receive his blessing.
Letter to Henri Tempier, 10 October 1832, EO VIII n 436