32 CENOZOIC MAMMAL HORIZONS OF WESTERN NORTH AMERICA. 



Gidley, Douglass, Peterson, Sinclair, and others, was prepared by 

 Dr. W. D. Matthew (May, 1906), and embodies some alterations 

 by the writer and by Messrs. Peterson and Douglass (September, 

 1906). It is to be regarded as largely tentative and incomplete. 

 Figs. 1 and 13 bring out the following two facts of chief importance: 

 First, that through examination and comparison of the fauna of 

 local horizons we shall probably be enabled to establish a complete 

 continuity of mammalian life for the entire Eocene, Dligocene, and 

 Miocene epochs of North America in a general sense, but this will 

 never apply to the fauna of the whole Tertiary of either the Great 

 Plains or the Mountain Region. 



Second, that while the chief faunistic lacunse at present are in the 

 American Pliocene, these gaps will probably be filled as time goes on, 

 just as the great lower Miocene gaps which existed only a few years 

 ago have been filled. 



