hi,
on your other current thread re your John DAVIS, his father is noted as James DAVIS a widower and the scribe did not record details for John's mum. I suspect John's mum and her family (her Dad and/or her brothers) may have been deceased or at least their SURNAME was not known to John for many years, for him, as an adult, to not know either his mum's given or nee name when asked by that clerk, especially as John was able to provide his own baptismal records to that clerk (see Debra's post re the info recorded on the page that followed the one you uploaded).
http://www.rootschat.com/forum/index.php?topic=795576.0From John's New South Wales death cert (or official transcription) and/or his marriage cert (or official transcription) or on birth certs for his children ... the church registers often have far more detail than NSW BDM summary registrations .... what information is given about John's origins ... NSW BDM civil registration commenced in 1856. Those clues should be very useful to the regular RChatters on this Oxfordshire Look Up board.
Online free to search NSW assisted passage ... per Elizabeth (3) 1845, unmarried Males start at page 9, alpha by surname.
https://www.records.nsw.gov.au/archives/collections-and-research/guides-and-indexes/assisted-immigrants-digital-shipping-lists NSW BDM
http://www.bdm.nsw.gov.au/Pages/family-history/registry-records.aspx SCROLL down to the heading re information available since 1856
and then scroll down further to information available prior to 1856
So, as I understand it, from the 1845 disposal certificate documentation on your other current thread, your John Davis' dad was alive at that time. Here on this new thread I think you are asking about that Dad ... perhaps as you cannot find any supporting 1841 census entry for that ... - James DAVIS was listed on that 1845 document as a Shiphand ... so possibly he was not enumerated on the 1841 census as perhaps he was at sea.
I should also note that John DAVIS was recorded as age 27 on that March 1845 record... so perhaps several years older than a lad born in 1820.
JM