Yochelson, Ellis Leon 1928-2006 The lower Ordovician gastropod Ceratopea / by Ellis L. Yochelson and Josiah Bridge. -- Washington : United States Government Printing Office, 1957 - P. 281-304, [3] h. de lam. -- (Geological Survey Professional Paper ; 294-H). Subjects--Topical Terms: Gasterópodos fósiles Universal Decimal Class. No.: 564.3