Since the time when Agassiz and Buckland made known the former presence of glaciers in the mountain valleys of North Wales, much has been written concerning the glaciation of Snowdonia, but comparatively little attention has been given to that of Western Carnarvonshire. This part of the country stretches south-westwards as the broad promontory of Lleyn between Carnarvon Bay and Cardigan Bay. Western Carnarvonshire for the most part lay outside the paths followed by the native glaciers. None of the larger valleys of Snowdonia trend in this direction, and so the marks of recent glaciation are not so fresh and striking in this region as they are further east. Hitherto no one has attempted to give any detailed account of the Drift deposits over the whole of Lleyn, but various references to the glaciation of the region are found scattered in the literature dealing with the geology of Wales.