File:Alpena County Courthouse - Alpena Michigan.jpg

DescriptionAlpena County Courthouse - Alpena Michigan.jpg English: The Alpena County Courthouse at 720 Chisholm Avenue in Alpena, Michigan, United States

DescriptionAlpena County Courthouse clock detail - Alpena Michigan.jpg English: The Alpena County Courthouse at 720 Chisholm Avenue in Alpena, Michigan, United

shell from the Potter Farm Formation (Middle Devonian, Givetian) in Alpena, Michigan. Stromatoporoid side view showing laminae and pillars; Columbus Limestone