I have found that nearly all references to Llandysilliogogo (or similar spelling) are related to the Cardiganshire parish. But ...
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http://en.wikipedia.org/wiki/Menai_Bridge gives the following info:
"Menai Bridge (Welsh: Porthaethwy) is a small town and community on the Isle of Anglesey in north Wales. It overlooks the Menai Strait and lies by the Menai Suspension Bridge, built in 1826 by Thomas Telford. It is the third largest settlement on the island, with a population of 3,850,[1] and occupies the area of the former parish of Llandysiliogogo, whose former church continues in use as a mortuary chapel (see below). ...
Attractions in Menai Bridge include the 14th-century Church of St Tysilio."
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Also " WELSH NOMENCLATURE - J. G. R. writes to the Mercury- "In Rowland's Mona Antiqua Restaurata' (second edition, p. 357) the name of the parish near Menai Bridge is given simply as Llanfair Pwll Gwyngyll,' -and he adds the remark, 'A rectory, in the bishop's gift, hath one chapel under it. viz., Llandisilio.' I believe the name given by Mr Grove, however, to be the full correct name, and, uncouth and barbaric as it may appear, it is or was highly appropriate and distinctive, meaning, as I have been informed on the spot, St. Mary's Church of the pool of the white hazels near the pool of St. Tysilio Gogo.' The first-mentioned pool is, no doubt, that near the railway station. The white hazels have probably long disappeared. The second pool must be the whirlpool in the straits near the ancient chapel, between the two bridges, caused by the meeting of the tide from opposite directions."
- from the North Wales Express 11th January 1878
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My suggestion is that any pertinent information for THIS parish be added here, especially for those of us researching this parish. Rev. John Jones, the brother of my great grandfather, Rev. Thomas Morgan Jones, "served" here from 1872 to 1879, I believe.
Thanks
Richard PJ