Heraldic Visitations of Wales and part of the Marches, by Lewys Dwnn, is the "Bible" of Welsh genealogy. Like that other Bible, it is most often quoted, but not often actually read. "Lewis Dwnn" first published in 1586 genealogies from three counties of South Wales. [Carmarthen, Pembroke, and Cardigan] Between the years 1586 and 1613, it was the life of Lewys Dwnn, the "Deputy Herald At Arms". It is written in Welsh with English footnotes. [It takes some time to get use to reading it!] It was first published in 1846 by Sir Samuel Rush Meyrick, and became the record of many Welsh families. In 2005, it was reprinted in Wales by Bridge Books and made available to the genealogy world.
Volume I : Counties of Carmarthen, Pembroke, and Cardigan
Pedigrees of Radnorshire Families
Pedigrees of Montgomeryshire Families
Volume II: Llyfr Achau (various family trees of Henry VII)
Three Counties of North Wales
Flintshire and Denbighshire Families
There is a glossary in Volume I for the benefit of the English reader. Large portions of the Welsh has been translated by Meyrick.
This reference is foundational to Welsh genealogy. The text has been reprinted: Bridge Books, 61 Park Avenue, Wrexham (LL 12 7AW) Get your Welsh genealogy "Bible" right here.