Article VI. — THE FAUNA OF THE TITANOTHERIUM 

 BEDS AT PIPESTONE SPRINGS, MONTANA. 



By W. D. Matthew. 



The American Museum Expedition of 1902 in western 

 Montana had for object to make a further search in the Ter- 

 tiary deposits of that region, where Mr. Earl Douglas has 

 recently discovered many new and interesting fossil mam- 

 mals. In the White River formation near Pipestone Springs, 

 Mr. Douglas had found a very interesting micro-fauna, and 

 our collections at the same locality, which Professor Osborn 

 has kindly turned over to me for study and description, 

 enable us considerably to extend the list. I am indebted to 

 Mr. Douglas for the opportunity to examine the type speci- 

 mens of his various species, as well as for the information 

 concerning localities, etc., contained in the stratigraphic part 

 of his very excellent memoir recently published on the White 

 River of Montana. 



The majority of the species are small or minute forms, not 

 found in the Titanotherium Beds of South Dakota or Colo- 

 rado, where the scanty fauna is almost entirely of large ani- 

 mals, — Titanotheres, Elotheres, and Rhinoceroses. A few 

 small species have been described from Swift Current Creek, 

 Canada, based on very fragmentary materials. The Pipe- 

 stone Springs fauna is therefore of much interest, as it illus- 

 trates the direct precursors of the numerous small species of 

 the Oreodon Beds. In the species from the three successive 

 stages of the W^hite River we have the most favorable oppor- 

 tunities for study of the details of evolutionary progress in a 

 given race that are presented among fossil vertebrata ; for the 

 materials'afe abundant and complete, the succession is un- 

 questionable, and the character of the beds, and hence the 

 local conditions of deposition, very uniform, so that we get 

 the same facies of the three faunas. It is doubtful how far,, 

 if at all, the Eocene deposits of the Rocky Mountain divide: 

 and foothills contain the same facies of their respective 



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