l6 SMITHSONIAN INSTITUTION 



Miocene and Oligocene fossils. In the few days spent here we secured 

 a small but interesting collection especially rich in the larger merycoi- 

 dodonts, of which several skulls and a considerable part of the skele- 

 ton of one individual were found (fig. 13). 



Having collected in all outcrops in the vicinity of Canon Ferry 

 we next moved to White Sulphur Springs, where the Deep River 

 formation of Miocene age was explored. In fossil collecting, ground 

 devoid of vegetation and debris always offers the best opportunity, 

 for in such areas the occurrence of specimens can be more easily 

 detected. Of the several miles of escarpment of the Deep River for- 

 mation along Smith River it is only here and there that ground is 

 thus denuded, and although specimens are fairly abundant, our work 

 was again hampered by the small size of the outcrops. A considerable 

 number of desirable specimens were obtained, but so much time was 

 spent in traveling from one area to another that with the completion 

 of this work we decided to abandon further collecting in the Tertiary 

 of Montana. 



The material assembled at Belgrade was boxed and shipped, and 

 upon receiving authorization to transfer our activities to the Wasatch 

 formation for the remaining part of the season, we started for Basin, 

 Wyo., some 300 miles distant, on June 27. Basin, the county seat of 

 Big Horn County, is a small town on the eastern edge of the badland 

 country in which we proposed to work. The Big Horn Basin has 

 long been known as a rich field for the remains of Eocene vertebrates, 

 and as the Wasatch badlands cover an area approximately 60 miles 

 long and 40 miles wide, our worries in regard to restricted collecting 

 grounds were over for the season. 



The term " basin " as applied to many of these Tertiary fields is 

 just what the name signifies — a low. central area, the sides of which 

 are formed by mountain ranges. The central part has been filled 

 with stratified layers of rocks, and it is in these layers that the fossil 

 bones occur. In the case of the Big Horn Basin, the deposits are 

 made up of materials derived chiefly from the erosion of the sur- 

 rounding heights. 



Acting upon the recommendation of William A. Stein, an ex- 

 perienced collector thoroughly familiar with the region, we com- 

 menced work on the breaks along South Fork of Elk Creek on the 

 eastern side of the basin. Confining our efforts to the lower part of 

 the formation on the eastern side of the basin, we successively worked 

 the badland escarpments of South Elk Creek, Fifteen Mile or Cotton- 

 wood Creek, Ten Mile Creek, and Five Mile Creek. The latter part 

 of the season was given over to the Middle Wasatch as exposed along 



