E-Flora BC: Electronic Atlas of the Flora of British Columbia

Species description:
The genus name derived from the down-pointing sporangium mouth that "looks" down. The species name referring to the shiny black sporangium.

Reproduction:
Producing abundant, glossy black sporophytes in summer.

Distinguishing characteristics:
With sporophytes, this plant is unmistak­able: the tiny, black, subspherical sporangia that are inclined at right angles to the seta are unlike any other local moss. Without sporophytes, the usually regularly three-ranked, narrowly triangular leaves, and the dense, dark green tufts, found mainly in calcareous moist habi­tats, are enough to identify this moss.

Habit:
Forming densely packed, dark green turfs.

Similar Species:
In the seepage habitat Philonotis and Pohlia, if lacking sporophytes, might superficially suggest Catoscopium but their leaves are never in three distinct rows and plants are rarely dark green. Meesia triquetra has leaves in three rows but the plants are more than twice the size of Catoscopium, the leaves also diverge out strongly (rather than weakly, as in Catoscopium) and have toothed margins. Meesia uliginosa and M. longiseta generally have sporophytes that are pear-shaped, sub­erect and not glossy black.