I would be interested in talking to you more about this family. There are a couple Pennsylvania Munley/Manley families in the census records with Cormac as a given name. Also, my own great-great grandfather was from the Belmullet area in Erris. My ancestor's family emigrated to the Pensylvania coal mining area.
I am the administrator of the Manley y-DNA surname project at familytreeDNA.com . http://www.familytreedna.com/public/Manley/default.aspx
We are slowly building a fairly good database of y-DNA of the descendants of the Mayo ancestors with Manley, Munley, Monnelly, and Munnelly as their surname. As part of that effort, I am also collecting family trees of emigrants to the US who can trace their families in Mayo.
Both of these efforts are necessary if we are to connect these families.
Marianne Manley Granoff