gtrrtaflltfjjia (tknthrrak THIRD SERIES, No. XXXIIL—JANUARY, 18G3. MONA MEDIiEVA.—No. XXVIII. HOLYHEAD. The church of this parish, which constitutes the only mediaeval building actually standing within it, was for¬ merly collegiate; and, with those of Llanfaes, Penmon, and Llanddwyn, made up the four religious houses existing in the isle of Mona. It is peculiar in its situa¬ tion, being erected within a portion of what seems to have been a Roman fortified station. Round two sides of the churchyard the Roman walls, very similar in their work to those of Segontium, still stand ; but part has been washed away by the sea, and part removed, in former days, for building purposes. It is highly pro¬ bable that the Romans had a trajectus to Ierne from hence ; and that, at all events, they knew the value of the locality as an harbour of refuge, and protected it accordingly. The lines of road from Conovium and Segontium converge at a spot where a small camp stood, still called Caer Helen, a little to the east of Four-Mile Bridge. Here the road crossed, either by ford or ferry, the narrow arm of the sea, and ran on to what was afterwards called Caer Gybi." It may also be conjec¬ tured that the Romans made use of the British camp on the summit of the mountain for exploratory purposes; but no positively distinctive traces of their operation have been observed, though on this mountain British 3bd ser., vol. ix. 1