Manuscripts, [late 12 cent.]-[early 20 cent.], formerly part of the library of the Mostyn family of Mostyn Hall, Flintshire, comprising transcripts and extracts from Giraldus Cambrensis, Geoffrey of Monmouth, Dares Phrygius, Nennius, Gildas, David Jenkins (Judge Jenkins), Sir John Wynn of Gwydir, Lydgate's 'Life of Our Lady', Leland's Itinerary, 'Chroniques de France', historical manuscripts such as Brut y Tywysiogion and Brut y Brenhinoedd, Welsh romances and the Mabinogion; collections of mainly Welsh poetry, among them the seventeenth-century volumes Llyfr Coch Nannau and Llyfr Gwyn Corsygedol, containing poems by Dafydd ap Gwilym, Guto'r Glyn, Tudur Aled, Siôn Cent and others; genealogies, pedigrees and histories; official papers relating to Caernarvonshire; catalogues of the Mostyn and Gloddaeth libraries, 1692-1842; etc.