ID Remarks: This species is either Peltigera gowardii or P. aquatica. The older species concept and nomenclature of, Peltigera hydrothyria, is used here to specify an aquatic species of Peltigera but it does not specify which of the two species it can be per Miadlikowska J., Richardson D., Magain N., Ball B., Anderson F., Cameron R., Lendemer J., Truong C., Lutzoni F. 2014. Phylogenetic placement, species delimitation, and cyanobiont identity of endangered aquatic Peltigera species (lichen-forming Ascomycota, Lecanoromycetes). American Journal of Botany 101:1141-1156 'What used to be considered a single species, Hydrothyria venosa, then two species, Peltigera gowardii (western N Am) and Peltigera hydrothyria (eastern N Am), is confirmed to have three supported clades. The third species is described formallly, Peltigera aquatica, an action that is sure to be controversial among practicing field lichenologists in the PNW, simply because P. aquatica occurs with P. gowardii, but is indistinguishable morphologically or chemically. This action has made it impossible to identify western Hydrothyria without DNA sequencing, if you accept the three-species documented by this paper.' B. McCune, NW Lichenologists website (20200518).