Sorry to disappoint anyone who was hoping to find Melinda's parents, but sadly I am not certain who they were.

I can however speculate, knowing what little I do about the Hurn family, and Melinda in particular.
Melinda was born in either 1792 or 1796 depending on whether the Holbeach Cemetery Burial Register or the 1851 and 1861 census returns are to be believed. The Burial Register states that she was 75 when she was buried in 1867, implying a 1792 birth date. The census returns meanwhile both suggest that perhaps 1796 is correct.

This offers two possibilities regarding her parentage:

David Hurn and Jane Clayton.

If this is correct, and asssuming that Jane was 20 when she married then she would have been in her 50s when Melinda was born. However we must bear in mind that John and Melinda's daughter was christened Jane Clayton Norris.

David Hurn and Margaret Mouseley.

David, born in 1775, was the son of son of David and Jane (above), but may only have been 17 years old when Melinda was born.

Take your pick. Perhaps I am totally wrong and there is another solution, though I tend to think that she was born in 1896, with David and Margaret as parents, but who knows?

Besides being a farmer in Holbeach, David Hurn was also a poet, and had a collection of poems published under the title "Rural Rides" in 1813, just two years before he died at the age of 40.