3. NONIUS MARCELLUS,[119] a Peripatetic, of Thubursicum in Numidia, is identified by Mommsen with the Nonius Marcellus Herculius of _C.I.L._ viii. 4878 (date A.D. 323); but nothing is known of his life. His work, _De Compendiosa Doctrina ad Filium_ in twenty Books (of Book xvi. the title only is known; Book xx. is fragmentary), though modelled on that of Gellius, is immeasurably inferior in execution. According to the theory usually received Nonius borrowed largely from Gellius; but it is possible that both compilers made independent use of the same authorities, viz., scholars such as Verrius Flaccus, Valerius Probus, and Suetonius, whose works they knew either directly or through abridgments. The subjects with which Nonius deals are grammar, lexicography, and antiquities; and he is often our sole authority for the titles of works as well as for brief extracts. 4. AMBROSIUS THEODOSIUS MACROBIUS, doubtless identical with the Macrobius who held, among other high offices, the proconsulship of Africa A.D. 410, was probably, like Nonius, of African origin. Besides his commentary on the _Somnium Scipionis_ of Cicero, Macrobius wrote a work in seven Books on Roman literature and antiquities with the title of _Saturnalia_. The imaginary conversations of which it consists are supposed to take place during the festival of the Saturnalia at Rome (hence the title); and the chief subject of discussion is the poetry of Virgil. A remarkable feature of the book is its wealth of quotation from Greek and Latin authors. Macrobius, like Gellius, bases his work on extracts from older authorities; but, unlike him, arranges his matter systematically. 5. AELIUS DONATUS, a grammarian who flourished at Rome about A.D. 350, and was one of Jerome's teachers, extracted from the lost work of Suetonius the Lives of Terence and Virgil, and prefixed them to his own commentaries on Terence and on the _Georgics_ and _Aeneid_. The latter is lost, and the commentary on Terence contains much that is not from the hand of Donatus. 6. SERVIUS.--There are two versions of the Servian commentary on Virgil. The shorter is the work of Maurus Servius Honoratus, who was born about 350 A.D., and lived at Rome (Macrob. _Saturn._ i. 2, 15); his topographical references show that he composed his commentary there. Servius, whose notes are chiefly on the language of the poems, gives illustrative quotations from Roman authors, in some cases from memory and inaccurately. Donatus is the authority whom he mentions oftenest, but he undoubtedly made extensive use of Suetonius. The longer version contains learned additions to the work of Servius by an anonymous Christian writer, who deals mainly with the subject-matter of Virgil.