I wouldn't presume to tell you how to pronunce Seagoe, but here is a wee scrap of information. My subscription to Emerald Ancestors ran out yesterday, but they have 1 marriage for Samuel Shanks in 1857 marrying a Jane?,Co. Armagh and 1 Jane Robinson in 1857 marrying
a Samuel?,Co. Armagh. This makes me think this is their marriage!! Armagh Ancestors has one marriage for Samuel Shanks in 1857 which you can view for 5 euros. Probably worth it. Mary was born before civil registration of births, so you would have to look at church records. I would go for the marriage record first and that will tell you the church in which they were married.RosemaryJoan