ILLUSTRATIONS 



Figures 



Page 



1. Diagram showing the relative abundance of identified individuals of 



the various orders and families of mammals in the National Museum 



collection from the Gidley Quarry 60 



2. Comparison of relative abundance of families of mammals at various 



localities in the Crazy Mountain Field, Mont 60 



3. Histograms illustrating Cabrera's law as applied to the Gidley Quarry 



fauna 66 



4. Histogram of measurements of second lower molars of all Lebo speci- 



mens of Metachriacus 66 



5. Histograms of typical variates of multituberculates from the Gidley 



and Silberling Quarries 74 



6. Histogram and corresponding roughly fitted normal curve of length of 



P4 in Ptilodus montanus from the Gidley and Silberling Quarries 75 



7. Scatter diagram of length of Mi and length of P4 for all Gidley and 



Silberling Quarry specimens of multituberculates that show both 



of these measurements 75 



8. Left lower jaw of Ptilodus montanus Douglass 85 



9. Lower dentitions of Ptilodus douglassi Simpson, P. gidleyi Simpson, and 



P. sincl&iri Simpson 96 



10. Lower dentitions of Ectypodus grangeri Simpson, E. russelli Simpson, 



E. silberlingi Simpson, and Paredypodus jepseni Simpson 100 



1 1 . Part of lower incisor and fragment of jaw of Eucosmodon sparsus Simpson. 103 



12. Right lower jaw of Gelastops parens Simpson 110 



13. Right lower teeth and alveoli and right lower jaw of Gelastops parens 



Simpson 110 



14. Left lower jaw of Prodiacodon concordiarcensis Simpson 112 



15. Right lower jaw of Leptacodon ladae Simpson 113 



16. Left lower jaw of Leptacodon munusculum Simpson 113 



17. Left lower jaw of Myrmecoboides montanensis Gidley 118 



18. Right upper P^-M^ of Myrmecoboides montanensis Gidley 118 



19. Left lower jaw of Stilpnodon simplicidens Simpson 119 



20. Left lower jaw of Bessoecetor diluculi Simpson 122 



21. Left upper jaw of Bessoecetor diluculi Simpson 123 



22. Left lower jaw of Aphronorus fraudator Simpson 123 



23. Right lower jaw of Aphronorus fraudator Simpson 125 



24. Left upper jaw of Aphronorus fraudator Simpson 125 



25. Left lower jaw of Eudaemonema cuspidata Simpson 132 



26. Left upper molars of Eudaemonema cuspidata Simpson 132 



27. Left lower jaw of Elpidophorus minor Simpson 134 



28. Right lower jaw of Picrodus silberlingi Douglass 137 



29. Humerus of an unidentified fossorial mammal 140 



30. Right lower jaw of Paromomys maturus Gidley 150 



31. Left upper jaw of Paromomys malurns Gidley 150 



32. Left lower jaw of Paromomys depressidens Gidley 154 



33. Left upper molars of Palenochtha minor (Gidley) 160 



VIII 



