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The National Archives site for Tithes clearly does not have records for the parish of Loughcrew or any variant spelling. The 1837 Lewis Topographical Dictionarly has an aritcle on Loughcrew parish and refers to the Tithe taxes collected. The article mentions a couplke of leading citizens and when I search under J. W. Naper. There was a record in the parish of Moylagh which is just to the west of Loughcrew. I would suggest that you look for your ancestors in Moylagh parish. See links.