Hi David,
The scan of passengers & crew which I looked at had the left-hand-side edge cut off the image. Which meant no "Jas" showing. Did you see a different scan?
Also did you see the message I posted about the list of deserters in Jim Melton's book 'Ships Deserters 1852-1900' which lists approximately 10,000 notified desertions and other absences by seamen taken from notices in the Government Gazette and Police Gazettes?
It does seem more than a coincidence that a Mr Parker would be listed in the newspapers amongst the arrivals, when James Radcliffe is shown later with that name. But I don't know how he would have managed to have that recorded in print.
Sue