Mahoonagh/Castlemahon Parish

Is there anyone who can tell me what the modern day Parish name is for the Parish known as Mahoonagh/CastleMahon Parish in the early 1800's?

I have at last found the record of my ancestors' marriage in 1813 (Patrick Ryan and Mary Greene) and would very much like to have contact with someone perhaps from a local history group who could perhaps assist me further. 

Patrick was convicted of manslaughter at Rathkeale 1827 and transported to NSW  leaving behind his wife and six children!

He tried to get his family out to NSW to join him but Mary died before she could make the trip.  All the children appear to have joined their father only to have had him drown shortly after.  Patrick was a good and faithful and very much favoured servant here in the colony and I would very much like to know the circumstances of his crime of Manslaughter in 1827.  I have looked at newspapers of the time but have not had a great deal of luck.

Mary Greene died in the area in about 1836 or so.  I doubt if there would be a marker on her grave as the family were very poor but if anyone has information or would like to help me try to find out more about this litle family I would greatly appreciate it.

The witnesses to their marriage were one Patrick Greene and a David Clifford if that helps.

Thank you.