On highly disintegrated, siliceous or sandstone rocks.

Belgium: Mosan: RRR (†1962), Ard.: RRR (†1870).

Luxembourg: Lorr.: RRR (†<1850).

France: - .

Now extinct throughout the area of study.

Lit.: La66: 328-334, Diederich (1986a: 121-122), Lambinon & Sérusiaux (1985a: 88).