Good find, Frances. Yes, it does sound like Mary is a 2nd wife, which is quite possible given he was about 45 when he married Mary Callister in 1773.

I looked at the list of Lonan marriages in the Notebook and there is a marriage 22 Nov 1748 of a James [blank surname] to Mary Kewley. Timing is reasonable but I can't see anything more to either prove or disprove this. The first marriage (if it exists) might fit into a blank spot, or might be in another parish, or ???. Same for a (potential) death of a first wife. Whatever the truth is, it looks like there were no children.