CONTENTS 



Page 



Introduction 1 



History of this study and acknowledgments 3 



Previous work 6 



Part 1: Geology and faunas 12 



Geography 12 



Geology 14 



Stratigraphy 14 



General stratigraphic column 14 



Cretaceous-Tertiary transition 16 



Fort Union 20 



Structure 28 



Fossil localities and faunal lists 29 



General occurrence of fossil mammals 29 



The Gidley and Silberling Quarries 31 



The Scarritt Quarry 34 



Other important localities 35 



Serial list of localities 43 



Index to localities by section numbers 45 



Faunal succession and correlation 46 



Combined faunal list 46 



Faunal succession 48 



Correlation of mammalian faunas 52 



Ecology 56 



Notes on nonmammalian biota 56 



Mammalian facies 59 



The Gidley Quarry and ecological incompatibility 64 



Extent of knowledge of Middle and Upper Paleocene faunas 68 



Part 2: Classification and description of mammals 70 



Order Multituberculata Cope 70 



Affinities of the Multituberculata 71 



Methods of study 73 



Family Ptilodontidae Simpson 80 



Key to American genera of Tertiary Ptilodontidae 81 



Comparison of species 83 



Genus Plilodus Cope 84 



Genus Ectypodus Matthew and Granger 99 



Genus Pareciypodus Jepsen 102 



Genus Eucosmodon Matthew and Granger 103 



Order Insectivora Gray . 104 



Family ?Deltatheridiidae Gregory and Simpson 107 



Subfamily Didelphodontinae Matthew 107 



Genus Gelastops Simpson 107 



Family Leptictidae Gill 111 



Genus Prodiacodon Matthew 112 



Genus Leptacodon Matthew and Granger 113 



Genus Myrmecoboides Gidley 115 



T 



