I know, I was commenting on Mark’s mention of id. For an example with the render transform, see opacity artifacts in line segments - #2 by Fil. We don’t recommend using that route though, because it’s much more complicated that needs to be.
In your case, you could set a specific ariaDescription option on the mark you want to target, for example ariaDescription: "informational dots about cities".
Then select this marks’ dots with, for example:
d3.select(map).selectAll(“[aria-description^=informational] circle”);
In a sense this works like the desired className, except it’s “hijacking” the aria-description property—and as a consequence it’s recommended to set the contents of that property to a semantically correct sentence.