An ancient and now almost obsolete remedy in the English law. An assize of mort aVancestor was a writ which lay for a person whose ancestor died seised of lands in fee-simple, and after his death a stranger abated; and this writ directed the sheriff to summon a Jury or assize, who should view the land in question and recognize whether such ancestor were seised thereof on the day of his death, and whether the demandant were the next heir.