Thelidium perexiguum (Müll. Arg.) Zahlbr.

Syn.: Sagedia perexigua Müll. Arg.
Lichenised. Poorly known taxon.
Substrate: calciferous rocks
Altitudinal distribution: submediterranean/colline belt (potential vegetation: mixed deciduous forests dominated by Quercus and Carpinus)
Note: a species resembling Staurothele rupifraga, with a very thin, lead-grey to bluish grey thallus, minute, entirely immersed ascomata, and 3-septate obovoid ascospores (to 35 µm long); on limestone at low elevations; only known from the Western Alps (France).
France: Haute-Savoie;