Hi there,
Could you please post your message on the Killallaghtan parish page here: http://www.irelandxo.com/group/killallaghtan-galway
There are Roman Catholic church records for the diocese of Cappataggle (Clonfert) (which is where Killallaghtan is situated). These start from 1809 for baptismal, marriage and burial records. You can access these at the National Library of Ireland, Pos. 2431, or the Church of Latter Day Saints ref. no. 1279215, 1279216. If you have any difficulty, you could try writing to the parish priest for more assistance.
There is also a list you might be interested in dated 1806-1810: Catholic householders, Killalaghtan; in the Catholic parish registers of Cappataggle, NLI (National Library of Ireland) Pos. 2431.
There are estate records which cover the area. The landlord was Barons Clonbrock Dillon. Check the NLI Ms. 19501. These cover the period 1801 to about 1844. This might seem early in date for you, but perhaps your ancestors were still living in the area at this time.
For 19th century, you could also try checking the land records called the Tithe Applotment Books (1823-38) or the later Griffth's Valuation (1848-64). Griffith's is freely available here: www.askaboutireland.com or here: www.failteromhat.com Failte Romhat has lots of other useful links you could try looking at.
Civil registration records are available from the General Register Office (GRO). These start from 1864 however. You can access the website here: http://www.groireland.ie/research.htm
Please make sure you link anyone else in your family who is interested in their Irish heritage to our site - and indeed anyone else you know of Irish heritage.
Kind regards,
Sinead Cooney
Genealogist (Ireland XO)