Funaria hygrometrica, Cord moss.
I have probably seen it before; it's common enough. But I had never noticed how the stems curl. I thought it was from the weight of the ripening spore capsules; the brown, dry ones are standing upright. I was jumping to conclusions, and got it wrong, as so often happens.
Half an inch high, if that. That big green leaf in back is a small cloverleaf.
This moss is also known as Water-Measuring Moss, because in dry weather, the mature stems curl and twist. "Dry weather", here in the spring, probably means any day it's not actively raining. These plants were on a smear of gravelly soil, hard-packed, and thoroughly dry.
Green capsules, fat and luscious, and brown capsules, wrinkled and open at the end, the spores already dispersed.
Companion flower, Common Draba or Whitlow grass. About as tall as my little finger.
If you look closely to the right of the flower; you can see the base of the moss, like small brown vases with one stem apiece.
Looking for info, I found a nice site with almost 200 photos of mosses arranged in alphabetical order. A quick, easily scanned reference, very handy.