Thelidium

Thelidium is a genus of lichen-forming fungi in the family Verrucariaceae. The genus was established in 1855 by the Italian lichenologist Abramo Bartolommeo Massalongo, who distinguished it from related genera by its point-like fruiting bodies with distinctive double walls and granular spores. These lichens form thin crusts on rock surfaces and reproduce through tiny, black, flask-shaped structures that contain spores. The genus includes about 27 species found worldwide, ranging from common European species to more recently discovered ones from Asia and Australia....read more on Wikipedia.