Drevotella proteana, a new genus and species of colonial hydrozoan, is described from the Middle Pennsylvanian Francis Creek Shale of the Mazon Creek area of northeastern Illinois. It is represented by numerous specimens preserved in iron-stone concretions in which the large, irregularly branched colonies appear as flattened impressions visible by virtue of color contrast Includes bibliographical references (p. 6-7) Drevotella proteana, a new genus and species of colonial hydrozoan, is described from the Middle Pennsylvanian Francis Creek Shale of the Mazon Creek area of northeastern Illinois. It is represented by numerous specimens preserved in iron-stone concretions in which the large, irregularly branched colonies appear as flattened impressions visible by virtue of color contrast 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-)