τῶν ἀποκρύφων.  The sense in which Cyril uses this term may be learned from Rufinus (Expositio Symboli, § 38), who distinguishes three classes of books:  (1) The Canonical Books of the Old and New Testaments, which alone are to be used in proof of doctrine; (2) Ecclesiastical, which may be read in Churches, including Wisdom, Ecclesiasticus, Tobit, Judith, and the Books of the Maccabees, in the Old Testament, and The Shepherd of Hermas, and The Two Ways in the New Testament; (3) The other writings they called “Apocryphal,” which they would not have read in Churches.  The distinction is useful, though the second class is not complete.