Hi Dannielle,
From the position of the mcfarline plots I would guess that they are older burials. However, it's possible that when James died they opened up the plot, as there is no stone we'll never know. The same with his wife Nellie.
There could be a mention of the burial place in the parish records, I have seen this in other parish records. I can't get to the library this week but I'll look at the records and see what it says. Unless you've already seen them?
Let me know
Jean