Hi there,
I only have ONE Ferguson:
Jun 1 1838 John, born to Patrick Ferguson and Catherine Corcoran, residence is Crossmolina town. Witness were Alex ?? and Sarah Barrett
I had NO Whittly or Whittby or McRoberts surnames either. No Murdock or Duncans either.
Personally, the Whittby sounds like a Church or Ireland name. If you already KNOW they came from Crossmolina, I would look into other denominations such as the Church of Ireland records. I have Church of Ireland, but only a few and they are for early 1800s. I have no McRoberts, Whitby ect, and one Ferguson for COI:
Sept 13 1814, Marriage of Francis Ferguson and Sarah Huston of Ballina and Stonehall (Foxford Parish?).
The fact that they married in Belfast also suggests COI roots, not catholic. Of coarse, I could be wrong, but thats where I would be looking.
The Crossmolina DISTRICT, which is what is frequently seen in the Indexes, does not mean they were born in the Parish or town of Crossmolina-the district covers several parishes. Church of Ireland districts are no the same as the Roman Cath districts either!
The North Mayo site may have other church records-or more complete catholic records than what I have-for a fee they will do a search of there computerised records. Might be worth it to have them do a search for one of them-hopefully it with show what parishes they came from, and that will help you in your future research.
Good Luck Ali!
http://mayo.irish-roots.net/