For a long time, the treatise de metris by Aelius Festus Aftonius was attributed to Marius Vittorino (the wording de metris omnibus, as argued by Morelli, must be rejected in favour of a more canonical title). In fact, a fault in the archetype had led to the fusion of the initial part of Victorinus' Ars grammatica with the first book of the metrical treatise. Keil pointed out the problem of a significant lacuna in the apparatus (GLK 6, p. 31), but nevertheless chose to give weight to the subscriptio that closed the first book (MARII VICTORINI DE METRICIS DIDASCALICIS LIB. I EXPLICIT FELICITER) and assigned the entire work to Victorinus. There are rather two possible hypotheses: 1) the fusion of the two works was a decision by Marius Victorinus, who wanted to give continuity to his grammar treatise (which has come down to us mutilated) with a systematic treatise de re metrica; 2) originally the two treatises appeared in the fifth-century archetype in their entirety and in succession; the fall of a few sheets then determined the abrupt suture between the two works, and subsequent misunderstandings. [D. Di Rienzo]