Ropalospora viridis 
Rosette Pixie-cup Lichen 
Rosy Saucer Lichen 
Salted Shield Lichen 
Sarea difformis 
Scaly Pelt Lichen 
Scrambled-egg lichen 
Script Lichen 
Sea Ivory 
Shingled rock shield lichen 
Shrubby Cup Lichen 
Smokey-eyed Boulder Lichen 
Smooth Horn Lichen 
Smooth lungwort 
Smooth Rock Tripe 
Smooth-footed Powderhorn 
Soft Strap Lichen 
Southern Soldiers Lichen 
Spotted Dog Lichen 
Squamarina cartilaginea 
Squamarina gypsacea 
Star-tipped Reindeer Lichen 
Stereocaulon ramulosum 
Sterocaulon vesuvianum