I do have lots of "Marks" people in my tree, but unfortunately James Alfred is not one of them. It is possible however that they were related in some way. i.e. from the same area of Cornwall & settling in Mount Gambier. My (or I should say,my husbands) Marks family, came out on the Nestor as per the message board posting (abt 1854) They first arrived in Portland, stayed a few years and then moved to the Mount Gambier area.
If you think I might have any info that might help you please ask, I would be glad to help