We know very little about Nonius Marcellus.  The inscriptio to his De conpendiosa doctrina describes him as a peripateticus Tubursicensis, indicating that he was a man of letters (though probably a teacher rather than a philosopher per se) born at Thubursicum, which should most likely be identified with Thubursicum Numidarum (mod. Khamissa) in what is now north-west Algeria.  Dating him has posed certain problems: he is traditionally placed between Aulus Gelius, whom he cites, and Priscian, who cites him; recent studies based on linguistic elements, meanwhile, suggest that he may have been active around the year 400 AD or slightly later.  His sole surviving work is the De conpendiosa doctrina, a substantial, twenty-book lexicographical collection.  Contained within this text is also a reference to an Epistula a doctrinis de peregrinando.  Paolo Gatti has suggested that this letter may not have been independent work, but rather a dedicatory epistle ad filium: according to this theory, although it originally stood at the head of the De conpendiosa doctrina, it was lost in the course of transmission and has now left as its only trace the fourteen-word self-citation just mentioned.  [P. Gatti; tr. C. L. Caterine].