Conostomum tetragonum

Conostomum tetragonum, or helmet-moss, is a species of bryophyte found in Europe.

Shoots grow to a maximum height of 2 cm. Leaves are shaped like narrow spearheads and sharply pointed. Capsules are nearly spherical and 2mm long.

It thrives in acidic, rocky mountain soils, especially where there is snow cover for a large part of the year, and on summit ridges. It grows in continental Europe and in Scotland. This species became extinct in England in the 1950s.