the place name looks like it could be Llanwrda which was in Llandovery registration district at that time. But, very few Butler bmds in the district. There is a birth reg for Edith Constance D Butler in june qtr 1875, but also a death reg for her in march qtr 1881 in Cardiff registration district, so she doesn't appear on a census.
Agree with Valda - the marriage cert with details of John's father should help your search.
Cornwall: Allen, Bevan, Bosisto, Carnpezzack, Donithorn, Huddy, James, Retallack, Russell, Vincent, Yeoman
Cards: Thomas (Llanbadarn Fawr)
Glam: Bowler, Cram, Galloway, James, Thomas, Watkins
Lincs: Coupland, Cram
Mon: Cram, Gwyn, John, Philpot, Smart, Watkins
Pembs: Edwards (St. Dogmael's)
Yorks: Airey, Bowler, Elliott, Hare, Hewitt, Kellett, Kemp, Stephenson, Tebb