Status in Britain: Red Data Book
Additional: Wildlife and Countryside Act Schedule 8; European Red Data Book; EC Habitats Directive; Biodiversity Key Species.

This tiny but beautiful liverwort consists of a thickened central midrib usually obscured by delicate folded "wings". The wings are only a single cell thick giving them a delicate, translucent appearance. It is found in calcareous dune slacks around the Welsh coast. It is best seen in the autumn and early spring: at many sites it is submerged in winter due to flooding of the dune slacks, and in summer it's above ground parts dry up and disappear completely. It is thought to be perennial with new aerial growth arising each autumn from underground stems which survive the summer.

This is a rare plant in Britain and Europe, and Wales holds most of the British populations.