A septimal quarter tone (in music) is an interval with the ratio of 36:35, which is the difference between the septimal minor third and the Just minor third, or about 48.77 cents wide.
The septimal quarter tone can be viewed either as a musical interval in its own right, or as a comma; if it is tempered out in a given tuning system, the distinction between the two different types of minor thirds is lost.
[1][2] The Maneri-Sims notation system designed for 72-et uses the accidentals and for a quarter tone (36:35 or 48.77 cents) up and down.
The septimal quarter tone is tempered out by twelve-tone equal temperament, but not in any of 19-TET, 22-TET, 24-TET, or 31-TET.
22-TET and 24-TET offer a very close match to the septimal quarter tone.