What are chapter summary phrases called?

Question

Is there a name for the literary technique of opening a chapter with a series of summary phrases? An example from Three Men in a Boat by Jerome K. Jerome:

Chapter II

Plans discussed.—Pleasures of “camping-out,” on fine nights.—Ditto, wet nights.—Compromise decided on.—Montmorency, first impressions of.—Fears lest he is too good for this world, fears subsequently dismissed as groundless.—Meeting adjourns.

We pulled out the maps...

Other books I'm aware of that do this:

• To Say Nothing of the Dog by Connie Willis
• Going Postal by Terry Pratchett
• Making Money by Terry Pratchett

Answer 1

One traditional term for it may have been

• Argument

I'm basing this on the Loeb Editions of the Greek Dramas where there is a synopsis of the play presented at the beginning under the heading "Argument".

Those particular translations tend to be from the late 19th & early 20th Century though, and that usage of the term feels distinctly outmoded.

Rejecting terms like preface, introduction and forward, more mundane choices would be:

• Synopsis
• Summary
• Abridgement

A "classier" term could be:

• précis

NOTE: I do seem to recall there is a specific "old-timey" term for this, but it's escaping me at the moment.

Answer 2

Nicholas Dames, in an article in The New Yorker, calls them explanations, although he doesn't indicate if this is a technical term, or simply his own.

Explanations proliferated. Take “The History of Charlotte Summers” (1750), commonly attributed to Sarah Fielding, in which the languid Miss Arabella Dimple, lying half naked in bed, calls her maid Polly to fetch her “the first Volume of the Parish Girl I was reading in the Afternoon.”

Nicholas Dames, The Chapter: A History, The New Yorker, October 29, 2014