I searched the Irish Family History Foundation's database. It contains 12,000,000 surviving rcds for abt 65% of Irish counties. Rcds B4 1840 are sparse.
For Michael Riley B 1831 (exact) in Co. Meath, I found 3 B rcds. One had a father's name of Bernard, the other two had father's names of John. 75% of Co. Meath parishes were rcd'ng Birth/Baptisms but this date. Therefore, your chances that one of these is for your ancestor are good.
Google the Foundation's name to lead you to this database. Register, opt to be notified as rcds are added and browse. Pls post your search results to my genforum msg.