On limestone rock at the summit of Black Mountain.
Medulla is black, perithecia sunken in areoles. Spores are 18-27 X7.5 um, simple, hyaline.
A recent paper (Lendemer & O’Brien 2011) has split eastern and western populations into two species. Western populations are now Peltigera gowardii, while eastern populations stay P. hydrothyria. Further studies are needed to determine if western populations could be split even further, into a third species.