Hi Susan,
I've had a look around online, but I wasn't able to find anything on this stone. Have you been in touch with
Donegal Ancestry yet? They can probably point you in the right direction. You could also try
Donegal County Council, as they might have documents or information about the memorial stone. For more information about County Donegal graveyards and tombstone inscriptions, take a look
here.
I hope this helps! :)