Euripides, Cretans fr. 472a (Nauck, Tragicorum graecorum fragmenta: (see Snell’s 1964 edition of Nauck, pp. 680 & [1033]). The thoughtful scholar wonders what κἀποφώλιον (= καὶ ἀποφώλιον) has to do with the Minotaur. As the brilliant A. E. Housman remarked in the Proceedings of the Cambridge Philological Society back in 1890, the vicious monster “was by no means ἀποφώλιον, empty, idle.” I very much like Housman’s emendation to κἀποφύλιον, (“and sui generis,” “off-species,” “belonging to no [human] tribe”), so appropriate to the Minotaur. And for good measure, H. finds ἀποφύλιος already recognized as corrupted into ἀποφώλιος at Aeschylus, frag. 287.
Our fragment derives from two sources in Plutarch: Theseus 15, where it appears as σύμμικτον εἶδος κἀποφώλιον βρέφος, “a mixed figure, an idle/empty baby,” and De curiositate (Περὶ πολυπραγμοσύνης) 520c, which reads σύμμικτον εἶδος κἀποφώλιον τέρας, “a mixed figure, an idle/empty monster”. To many scholars, it has seemed inappropriate to refer to the frightful Minotaur as a βρέφος, a “baby;” τέρας is much better, but how do we explain the discrepancy in MS readings? The word τρέφος, “creature” is Nauck’s reasonable compromise: it’s easy to see how it might be corrupted to either βρέφος or τέρας.
To sum up: the most likely reconstruction of the line would seem to be σύμμικτον εἶδος κἀποφύλιον τρέφος, “a mixed figure, a creature belonging to no species.”