The great stage actor Marian Seldes died this week at the age of 86.

Seldes may not be a household name outside of the world of theatre, but she was very well-known as a stage actress with many successes on Broadway and beyond.

I never saw Ms. Seldes’s legendary New York stage appearances but I mentioned her over the years in acting classes as an actor who seemed most ideally suited to live stage performance. Her mere presence was a powerful dramatic statement. Seldes was tall and stately with a handsome angular face that was easy to read from a distance; these are perfect tools for a stage actor but sometimes too large for the screen (although she did appear on television and in a number of films).

Some of my students remembered that Seldes made a brief appearance as Big’s mother in an episode of “Sex and the City.” But it is her appearances in numerous stage plays by Edward Albee, Samuel Beckett, and Tennessee Williams, as well as productions of Equus, Deathtrap, Painting Churches, Richard III, etc., that cement her place in American theatre history in a career that spanned seven decades..

Although I missed her many New York performances, I was fortunate enough to see Marian Seldes in a live performance I will never forget. In November 2008, when I was presenting a paper at a Thornton Wilder conference at The College of New Jersey, a Friday afternoon session was an intimate readers’ theatre presentation of work by and about Wilder. Narrated by Tappan Wilder, Thornton Wilder’s nephew, the other performers were Marian Seldes, playwright Edward Albee, and poet Sandy McClatchy.

When I took my seat in the campus concert hall, Ms. Seldes was sitting quietly behind a grand piano at the back of the stage, carefully studying her script. Her concentration and presence were mesmerizing. When the performance began, it was electric to watch the interaction of Seldes and Albee, two legends who had carved parts of their legends in collaborations with each other. Each would have been 80 at the time.

It was a one-time performance and the small but rapt audience knew we were watching something special.

Playwright Sam Shepard once said that the thing he likes about theatre is that “it goes out into the air and disappears.” That November 2008 Wilder performance was a perfect illustration of that ephemeral quality of theatre.

And of a notable lifetime.