The late Cretaceous ammonites Scaphites leei Reeside and Scaphites hippocrepis (DeKay) in the western interior of the United States / by William A. Cobban.
Publication Info.
Washington : U.S. Department of the Interior, Geological Survey, 1969.
Washington : United States Government Printing Office
Title from title screen (viewed September 24, 2014).
Also available online in PDF format from the U.S. Geological Survey Warehouse (http://pubs.er.usgs.gov/).
Bibliography
Includes bibliographical references (pages 24-27) and index.
Note
"Three chronological forms each of Scaphites leei and Scaphites hippocrepis occur in dimorphic pairs and provide a means of correlating thin units of strata."