Archaeobatophora typa n. g. and sp. of the Upper Ordovician, Richmondian Big Hill Limestone from Delta County, Michigan, is described as a member of the Dasycladaceae. Although this alga is only weakly calcified along its main axis, its morphology is unusually well preserved and allows assignment to the extant tribe Batophoreae Includes bibliographical references (p. 39-40) Archaeobatophora typa n. g. and sp. of the Upper Ordovician, Richmondian Big Hill Limestone from Delta County, Michigan, is described as a member of the Dasycladaceae. Although this alga is only weakly calcified along its main axis, its morphology is unusually well preserved and allows assignment to the extant tribe Batophoreae Fieldiana series has been published as Geological Series by Field Columbian Museum (1895-1909) and Field Museum of Natural History (1909-1943), and as Fieldiana: Geology by Chicago Natural History Museum (1945-1966) and Field Museum of Natural History (1966-)