YSTRAD MEURUG, or Meyric, at the head of the valley of the Teifi, and commanding the pass leading over into Radnorshire.--Built by Gilbert de Clare when he reconquered Cardigan, and one of his most important castles.[934] Its importance is shown by the fact that it had a small stone keep, the date of which cannot now be determined, as only the foundations remain, buried under sods. There is no motte, and the bailey can only be guessed at by a portion of the ditch which still remains on the N. side, and by two platforms which appear to be artificially levelled. The castle is about three miles from the Sarn Helen or Roman road through Cardigan. *PONT Y STUFFAN, or Stephen's Bridge, near Lampeter.--Burnt by the Welsh in 1138, and not again mentioned.[935] In the outskirts of the town of Lampeter is--or was--a lofty moated tumulus (not shown on O.M.), and traces of a quadrangular court.[936] As it is also called Castell Ystuffan, it was probably built by Stephen, the Norman constable of Cardigan. There appears to be another castle mound at Lampeter itself, near the church. Lampeter was an important post on the Roman road up the valley of the Teifi. *NANT YR ARIAN.--This castle is only mentioned once, in the partition of Cardigan and Pembroke which took place in 1216, during the most disastrous part of John's reign.[937] There are two "castellau" marked at Nant yr Arian in the N. of Cardiganshire in the O.M.; neither of them look like mottes. This castle, as well as that of Ystrad Peithyll, seems to have been placed to defend the road from Aberystwyth to Llanidloes, which would be the chief highway between Shropshire and Ceredigion. CASTLES OF CARMARTHENSHIRE.