Hi Margaret,
If you haven't already,you could try checking the land records called the Tithe Applotment Books (1823-38) or the later Griffith's Valuation (1848-64). The Tithe Applotment Books (1823-38): Microfilm copies of the books for all of Ireland are available at the National Archives of Ireland (NAI) http://www.nationalarchives.ie/genealogy1/genealogy-records/tithe-applotment-books-and-the-primary-griffith-valuation/ or the Church of Latter Day Saints (LDS). 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.
Also you might try:
http://www.nationalarchives.gov.uk/records/looking-for-person/default.htm
Have you checked the immigration records in Australia? Often these records reveal alot of infomration concerning family left behind. Generally, more information was given at the port of arrival rather than the port of departure. The University of Woolongong has produced, on microfiche, a complete index and transcript of all information concerning immigrants of Irish origin recorded on ships' passenger lists between 1848 and 1867. These are useful for finding out an exact place of origin as well as parents' names. The Public Record Office of Victoria has good online databases of settlers at www.prov.vic.gov.au Otherwise, other records may be found in the Colonial Office Papers of the UK National Archives, class reference CO 201. This class contains a wide variety of records, including petitions for assisted passages, emigrants' lists, records of emigrants on board ship, petitions from settlers for financial assistance and much more.
You might also try the Mayo Genealogy Group http://www.mayo.ie/dnn/Blogs/Forums/tabid/92/aft/92/Default.aspx#.UHbSKxXA-Io
or one of the Genealogy Centres in Mayo for more assistance.
Mayo North Family History Centre,
Enniscoe,
Castle Hill,
Ballina,
County Mayo.
Tel: +353 (0)96 31809
Fax: +353 (0)96 31885
Email: normayo@iol.ie
Website: www.irish-roots.net/mayo/Mayo.htm
South Mayo Family Research,
Main Street,
Ballinrobe,
County Mayo.
Tel/Fax: +353 (0)94 9541214
Email: soumayo@iol.ie
Website: www.mayo.irish-roots.net
regards,
