Looking for Michael Lettice

I am looking for information on Michael Lettice, who may be my ancestor. I had been told that our family was from Meath, but recently I found a listing in IRELAND, TITHE APPLOTMENT BOOKS for Michael Lettice in 1826. My ancestor, Peter Lettis (possible spellings include Lettice, Lettis, Lettus, Lettuce) was the son of Michael Lettice (Lettis) and Catherine Finnan.

Michael and Catherine were both born in about 1785. Their  son Peter was born 28 Oct 1818. There were 4 other children in addition to Peter: Patrick (1819), Andrew C (1824 or 1827), James (1829), and Catherine (1828)

Peter came to the United States 31 Dec 1840. He was a potter by trade and settled in the Troy, New York area. 

I would appreciate any information you could give me. I think this is a wonderful thing you are doing--thank you for volunteering!

If any additional information would be helpful, I will try to supply it, but although I know a lot about Peter's life in the US, I know almost nothing about his life in Ireland. 

I did find some listings for Lettis in Griffith's but this would have been after the time Peter left the country and none of them were for his father's name Michael. 

I do know that Catherine Finnan Lettis eventually came to the US, because I found her in Troy, NY in the 1855 state census.

thank you!

Dorothy Lettus