Pen Dal-aderyn () forms the bold, wave-cut extremity of the
St Davids headland and is accepted by
Ordnance Survey mapping as the westernmost point of the Welsh mainland. Rising to roughly 26 m above Ramsey Sound, the
headland lies 3 km south-west of St Davids and is skirted by both the
Pembrokeshire Coast Path and a
National Trust strip that links Porthlysgi Bay to
Porthclais. From the clifftop the view spans the Bishops and Clerks rocks, the tidal race of "the Bitches" and the serrated north cliffs of Ramsey Island a kilometre offshore. The
promontory exposes the Treginnis Group of the late
Precambrian Pebidian Volcanic Series—purplish keratophyric lavas and associated
tuffs and
agglomerates that dip gently south-east beneath younger
Cambrian sandstones. Small quartz-copper
veins were trial-worked here in the nineteenth century; remnants of the Treginnis copper mine, including a part-infilled shaft just east of the point, are passed by walkers on the coast path. Recorded as Pen dal aderyn in 1843 and Trwyn Talderyn in 1840, the
toponym probably fuses tâl 'end" with aderyn "bird", yielding a sense of "bird-headland"; a later folk reinterpretation connected dal with "to catch", giving rise to the literal modern translation "bird-catching head". ==References==