Well, there goes that theory. This week I went to the State Library and looked up "Quarantined! The 1837 Lady MacNaghten immigrants" (by Perry McIntyre and Liz Rushen). It revealed that the Catherine Murphy who arrived on that ship was married to a Richard Murphy, and died in 1846. One Catherine Murphy excluded, dozens to go!
The book also had a couple of paragraphs on the Murnane family. Michael Murnane and Anne (nee Quinn) had three daughters old enough to be 'bounty' passengers - girls of marriageable age - as well as four younger children with them when they set sail. Sadly, one son died on the journey, and a daughter died during the time in quarantine in Sydney. What a terrible start to a new life in Australia.