This is my first observation at this place, a line of sand dunes on the Portuguese coast. I was a little disappointed with the small variety of lichens found here. In addition to Xanthoria, one or two species, and one species of Cladonia just found the species of this topic, which I think is Collena tenax. There was a (for me) non-expected amount of specimens of this species here. I saw dozens of them, many of them growing directly from the sand with no vegetation nearby and others with some moss around. The first indication of their presence was given by the presence of a cyanobacteria, of the genus Nostoc, that in some places accumulated. There aren't many species of Collema growing in soil. The best known is undoubtedly Collema tenax having a number of varieties. For the specimens of this observation the data seem to point to this species. The only alternative, given the form of the lobes, could be Collema bachmanianum. Apparently, in a superficial analysis of the photographs (see photographs attached), it appears that the margins of the apothecia are crenate and with small lobules, but a detailed analysis shows that the lobules develop from the base of the apothecia and not from the margin. In addition the data obtained for the average size of spores: Me = 19.8 x 6.7 µm ; Qe = 3 (N=21) are consistent with those of C. tenax and are shorter than those of C. bachmanianum.