Pope St. Cletus
This name is only another form for Anacletus, the second successor of St. Peter. It is true that the Liberian Catalogue, a fourth-century list of popes, so called because it ends with Pope Liberius (d. 366), contains both names, as if they were different persons. But this is an error, owing evidently to the existence of two forms of the same name, one an abbreviation of the other. In the aforesaid catalogue the papal succession is: Petrus, Linus, Clemens, Cletus, Anacletus. This catalogue, however, is the only authority previous to the sixth century (Liber Pontificalis) for distinguishing two popes under the names of Cletus and Anacletus.
There is historical evidence for only the last of these statements. The feast of St. Cletus falls, with that of St. Marcellinus, on 26 April; this date is already assigned to it in the first edition of the “Liber Pontificalis”. (See CLEMENT I, SAINT, POPE.)
LIGHTFOOT, Apostolic Fathers, Pt. I: St. Clement of Rome (2nd ed., London, 1890), 201-345; DUCHESNE, Liber Pontificalis, I, LXIX-LXX, 2-3, 52-53; HARNACK, Gesch. der alt-christl. Lit. bis Eusebius, II-I, 144-202; Acta SS., April, III, 409-11; DE SMEDT, Dissertationes selectæ in hist. eccles. (Ghent, 1876), 300-04.
J.P. KIRSCH (Catholic Encyclopedia)