Thank you so much for your responses. I understand more now I've seen that two page census in 1861 and that of 1871. However I’m not convinced on the McIntosh link.
Couldn’t this be possible:
James Christie and Ann Rough marry 01.07.1812 in Perth. They have James, Isabella, George, Richard, James - the latter being my line; I assume the first James dies.
‘My’ James marries Jane Sherwood, daug of George Shearwood (Shoemaker) and Margaret Young 15.10.1841 in Perth. James and Jane have Margaret, Jane, John, Ann, Agnes (my line), Isabella and James.
Agnes is born 02.02.1850 and her birth record shows Agnes Tough Christie, daug of James Christie , Printer, Perth and Jane Sherwood his spouse.
Otherwise wouldn’t she have been Agnes McIntosh Christie? Where else would the Tough/Rough have come from but the paternal grandmother’s maiden name though it was Agnes’s elder sister Ann who was named after the paternal grandmother.
I have the birth record of James Christie b. 18.07.1820, bap. 09.08.1820, son of James Christie (Gunmaker) and Ann Rough (who would become Tough) who are also named on the 1859 death cert of James.
Possible or am I still missing the obvious?
I know Agnes Tough Christie marries my ancestor Robert Eddie Thomson b. 02.04.1849 an they marry 05.12.1870 in Airdrie