Perhaps here because it is the cognomen of the poet Vergil (omicron 832); and note also e.g. Maron the eponymous founder of Maroneia (mu 222). However, this genitive case is evidently quoted from somewhere, and a likely candidate is Euripides' satyr-play Cyclops (line post 39F): M. is the Ismarian priest who gives Odysseus the skin of wine with which he in turn incapacitates Polyphemus (cf. Homer, Odyssey 9.197).