Frances, There are at least two possibilities (probably more). 1. The census could be in error. However, if she's born in 1844, then she would be 16 years of age in the 1860 census; her mother would have been 21 when she gave birth. Certainly no problem there. 2. Tombstone could be wrong? The whole family could be wrong? I doubt this. 3. She could be an "unknown" descendant. However, after looking at all the descendants from the Y males, I don't see how it is possible (pregnancies would be too close). It's more likely, that unless you discover an error in the dates you have, the census is incorrect. Certainly wouldn't be a first! Regards, Cousin Joyce