Pertusaria velata, synonym Varicellaria velata (Rimmed Wart Lichen)
Both photos (above & below) were taken at Mauthe Lake Recreation Area, Kettle Moraine South
Photo was taken at Pike Lake, Kettle Moraine State Forest Northern Unit

Photo above was taken at Observatory Hill State Natural Area
Both photos (above & below) were taken at Mt. Arvon, Michigan