Hi William,
This is interesting Samuel's wife Margaret is now called Mary, but her birth place is the same as the Margaret in the above 1851 Census. Maybe if you checked the children's birth's on SP you would get the parents marriage date. I believe it's usually on birth certificates.
1871 Census Dumfries Landward - Dumfries/ED: 4/Page: 14/Line: 13
Samuel Howatt 40, Head, Durisdeer, Dumfries - Shepherd
Mary Howatt 46, Wife, Crawford, Lanark
John Howatt 17, Son, Johnston, Dumfries - Shepherd
Mary J Howatt 13, Daug, Kirkmahoe, Dumfries
William K Howatt 9, Son, Dumfries, Dumfries
Agnes M Howatt 7, Daug, Dumfries, Dumfries
IGI has the children...
John Howat - 09/01/1856 - Kirkmahoe, Dumfries, Scotland
Mary Jane Howat - 05/12/1857 - Kirkmahoe, Dumfries, Scotland
William Kennedy Howat - 06/11/1861 - Dumfries, Dumfries, Scotland
Agnes McDonald Howat - 13/09/1863 - Dumfries, Dumfries, Scotland
1861 Census - Dumfries St Michael/ED:24/Page:3/Line:6
Margaret's age varies again. . . if it's the same woman she is 30 in 1861 BUT 46 in 1871!
Margaret McDonald 30, Wife, Dumfries - Shepherd's wife
John Howat 6 Son, Kirkmahoe, Dumfries
Thomas Howat 4 Son, Kirkmahoe, Dumfries
Mary Jane Howat 2 Daug, Kirkmahoe, Dumfries
Samuel is not with the family
Laurina