Part 3 of this study is concerned with bryozoan species from four limestone units (Mifflin, Quimbys Mill, Guttenberg, and Ion Formations); these rock units of Champlainian age (Middle Ordovician) are exposed in northwestern Illinois and adjacent parts of Iowa and Wisconsin. Representatives of the following genera are discussed: Homotrypa Ulrich (including 6 species, 2 variants), Orbignyella Ulrich and Bassler (one species), Prasopora Nicholson and Etheridge (2 species), Monticulipora d'Orbigny and Cyphotrypa Ulrich and Bassler (one species each).

GeoRef, Copyright 2004, American Geological Institute. Reference includes data from Bibliography and Index of North American Geology, U. S. Geological Survey, Reston, VA, United States