Planocarina marginata (Penard, 1902)
Diagnosis: Shell colourless, oval or pyriform, laterally compressed, composed mainly of oval or circular shell plates, often interspersed with small beads of organic cement. Shell with a small lateral ridge that begins just posterior to the aperture. Aperture oval and surrounded by a small but thickened lip.
Dimensions: Shell length 140–180 μm; width 110–150 (180) μm; aperture 25–40 μm.
Ecology: Wet Sphagnum mosses in Sphagnum-dominated peatlands.
Geographical distribution: Holarctic, and possibly even broader, as it has also been recorded from the Galápagos Islands and Africa—Annobón Island and Equatorial Guinea (Kosakyan et al., 2025).
Remarks: This species has a characteristic small lateral ridge, but the degree of development of this feature is not constant and likely reflects a wide range of variability. I have always found P. carinata and P. marginata occurring together.
These shell has been build from xenosomes, like a fragment of a diatiom (left hand arrow), the spine scale of Euglypha acanthophora (upper arrow) and plate scales of an Heliozoon (right hand arrow).
