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

[1] Shoots grow to a maximum height of 2 cm.

Leaves are shaped like narrow spearheads and sharply pointed.

[2] It thrives in acidic, rocky mountain soils, especially where there is snow cover for a large part of the year, and on summit ridges.

[2] It grows in continental Europe and in Scotland.