Recently I had an opportunity of paying a brief visit to the localities described by Miss Elles as affording a clue to the horizon of the Hirnant Beds. As I have for many years believed that the fauna of the Hirnant Beds is Ordovician, I was anxious to see upon what evidence the assignment of those beds to the Silurian was based. The Bwlch-y-groes locality was visited with Professor W. J. Pugh, University College of Wales, Aberystwyth, who will shortly deal with the structure of that area. It is sufficient for the present to state that this section has been misinterpreted by Miss Elles, and so far from proving that the Hirnant Beds lie within the Valentian, shows, if anything, that they cannot possibly form part of that series, which is fully represented there and has much the same characters as throughout Central Wales. To anyone thoroughly familiar with the Ordovician-Silurian succession of Central Wales, the structure and rock-succession of the Bwlch-y-groes Pass presents no difficulty and it certainly gives no support to the idea that the Hirnant Beds are of Lower Valentian age.