Manuscripts of, or collected by, John Edwards Griffith, [c. 1715]-1929, including pedigrees, memoranda and genealogical notes relating mainly to Anglesey and Caernarvonshire; a volume of pedigrees by John Ellis, Tai Croesion, 1723; manuscripts of William Williams, Llandygái; and some 350 letters, [c. 1892]-1929, to J. E. Griffith relating to botany and genealogy and to his publications.

Notes, transcripts and drafts of articles published by Egerton Phillimore, 1881-1937, relating to manuscripts, history, literature, genealogy, place-names, grammar, etymology and other linguistic matters, primarily concerning Wales but also including material pertaining to England, Scotland and Ireland, as well as continental Europe. Interspersed among the notes are occasional diary entries and drafts of letters, usually relating to the same topics, as well as containing personal material.