There's a common feature in old typography where the first word of a page is repeated at the end of the previous page, usually right-aligned on a line by itself. This book from 1759 shows this feature on nearly every page.
For example, page eleven could end with:
A sentence like this starts near the end of page eleven and
then
On page twelve you find:
then continues at the top of page twelve.
What do you call this feature?