Okay, that gives us something more to go on actual French records.
The death of Lucien Eugene was in Paris 2e, and he died at the residence of his parents, rue de La Michodière 12.
http://www.geneaservice.com/ I think shows a possibility for the marriage in France - in the 1798-1860 reconstructed records (Paris civil records 1860 and before were destroyed in a fire) - a mention of a Jane Watkins from Knighton. Without paying I cannot see more, but it looks to me if you look under Chauveau that there's an entry for a Louis Nicholas Chauveau, residence A????es, birthplace a bit cut off but might be 'Quarré-les-Tombes'.
I can't seem to find this on the Paris archives list of reconstructed records:
http://canadp-archivesenligne.paris.fr/archives_etat_civil/avant_1860_fichiers_etat_civil_reconstitue/index.phpHowever, if I look up Quarré-les-Tombes on the Yonne archives site (
http://archivesenligne.yonne-archives.fr/ ) I can find a Louis Nicolas Chauveau b. 22 August 1835. He was the son of Louis Elisabeth Chauveau (aged 29) and wife Pierrette Boussard
Having a look around a few places like
http://www.genealogie.com/ shows there were some possible siblings in Paris. As an example, I tracked down one, Marie Louise Chauveau, who married in Paris, 17e, 19 December 1874 (never know if these links will work, but
http://www.rootschat.com/links/01gdw/ and page 17)
She was born Quarres-les-Tombs, 28 Jan 1843, the daughter of Louis Chauveau, died at Asnieres, Seine, (
https://en.wikipedia.org/wiki/Asni%C3%A8res-sur-Seine ) 7 Feb 1862, and Pierette Boussard, his widow, residing place de Marche St Honore 28, present and consenting. The names of three children, born before the marriage, are listed (legitimised by said marriage). A brother of Marie, Eugene Francois, was a witness.
Now
Asnieres is an interesting place, because it looks to me like the residence written on that index card for Louis Nicolas Chauveau's marriage, and one reason for a marriage being in these records but not on the Paris archives list is that it actually took place
outside Paris, in one of the areas that would now be considered a suburb.
But actually the records will be not in Paris, but in the archives for Haut-Seine:
http://archives.hauts-de-seine.fr/archives/rechercher/archives-en-ligne/Sure enough, if you look at the indexes, there's a marriage for them there in 1858.
Go to 1858 marriages and they're on page 17 (ordering is a bit mucked up in these)
13 March 1858
Louis Nicolas Chauveau, employee, resident in this commune route d'Argenteuil, minor, born Quarre-les-Tombs 22 August 1835, son of Louis Elisabeth Chauveau, labourer, and Pierette Boussard.
Jane Watkins, maid (femme de chambre), resident in this commune rue de Courbevoie, born Knighton, Radnor, England, 30 September 1832, major daughter of George Watkins, carpenter, resident Knighton, and Jeanne his wife, deceased. (a bunch more legal stuff over the page, witnesses who all seem to be friends of Louis, not relatives, and everyone's signatures).