I search the IFHF's online database @ ROOTSIRELAND.IE. It has abt 19 million B/M/D and other records for MOST Irish counties. Records before 1863 are increasingly sparse. By 1800, they are nearly non-existant.
For a Tho(mas) Menton and Mary Kelly marriage 1890 +/- 7 yrs, somewhere in Ireland, with the parents' names unknown, I found 0 records.
For Tho(mas) Menton B 1867 +/- 5 yrs, ditto, I the same.
I wish this would help, but it doesn't. Suggest that you visit this website, register (free), opt to be notified as more records are added to the database. There is a (SLIM) chance records for your ancestors will be found.