viii Pi-eface. 



1. Uinta (Upper Eocene) subdivided by Peterson 

 into Telmatotherium and Diplacodon Horizons. 



2. Puerco (Basal Eocene) subdivided by Wortman 

 and Matthew into Puerco and Torrejon. 



3. Two other Eocene horizons determined and corre- 

 lated in the Huerfano Basin of Colorado by Osborn and 

 Matthew. 



4. Wliitc River (Oligocene) subdivided by W'ort- 

 man and Matthew by the addition of two upper di- 

 visions, Protoccras beds and LcptaiicJicnia beds. 



5. Hie three divisions of the White River, first made 

 by Hayden and Leidy, further defined and correctly 

 correlated with the stratigraphy, and the existence 

 shown of two contemporary faunal phases in each 

 division (W^ortman and Matthew). 



6. The various Mioeene formations which have been 

 grouped under the general names of Loup Fork and 

 Deep River, distinguished and correctly correlated with 

 their respective Miocene horizons, and the so-called 

 Palo Duro horizon eliminated (Matthew and Gidley). 



7. The ^olian Theory. — Our field researches 

 have resulted in replacing the lake basin theory by the 

 fluviatile and ctolian theory, especially under the ob- 

 servations of Dr. W. D. Matthew, the arguments de- 

 rived from which are fully summarized in his memoir. 



This demonstration has been nearly simultaneous 

 with that of Messrs. Hatcher, Davis, and Gidley, who 

 have reached and published similar results. 



8. Stratigraphical Succession of Horizons. — 

 The most complete paper on stratigraphical succession 

 is that by Matthew, No. 28, entided "A Provisional 

 Classification of the fresh water Tertiaries of the West," 

 summarizing results obtained by our field parties by 



