Like all of our Seligeria species, this one is very small, but dense patches of it on rock or stones often catch the eye when capsules are present as they are carried on setae that look very long for the size of the plants.
Seligeria species are most reliably identified when their capsules have matured, and close examination of the mouth of a dehisced capsule of S. pusilla with a good x20 lens will reveal obvious peristome teeth, although these are often quite short and stubby.
Beware confusion with the uncommon Brachydontium trichodes in upland districts. This moss has a similar appearance and size to S. pusilla, also has a peristome and grows in similar places. When fertile it is easily identified by its obviously furrowed capsules (when dry and empty).Read the Field Guide account