I've seen the 1891 census "Davis Town Ireland" reference, however another census return cites Mary Lyon's birthplace as "New Ross Wexford" (near the border with County Kilkenny). So "Davis Town Ireland" and "New Ross Wexford" are as specific as it gets, unless you know otherwise.
And just to manage expectations, even if you manage to more conclusively establish birth location and maiden name, there's no guarantee you will find a church baptism record for Mary.
That said, from what I can see in the census returns, Peter and Mary's oldest child was Mary born c.1868. A couple of census returns cite "Lyon" rather than "Lyons". Either way, the closest
potential "matches" for a marriage couple that I could find on Freebmd were:
- Peter Lyon and Mary Ann McConvill, both listed under "Marriages Sep 1865", Liverpool registration district, volume 8b, page 190; and
- Peter Lyon and Mary Hamilton, both listed under "Marriages Dec 1866", Liverpool registration district, volume 8b, page 228.
An online family tree suggests it is the Lyon / Hamilton marriage (***health warning, information placed online by individuals may be inaccurate!). That marriage took place on 10 December 1866 in St. Nicholas Church Liverpool, both Peter and Mary were living in Slade Street at that time, groom's and bride's fathers were recorded as Peter Lyon and James Hamilton, both labourers.
As Dathai mentioned above, you need one of the children's birth certificates to confirm Mary's maiden name, unless someone can post something more here to move things forward (here's hoping).
