GEOLOGIC THEORY AND METHOD 265 



Wind Eiver. But it must not be supposed that normal sediments do not 

 occur. In a recent Bulletin of the American Museum, evidence has been 

 presented to show that the Bighorn and Wind River basins, formerly 

 regarded as lakes, are really structural troughs surrounded by uparched 

 pre-Tertiary rocks, the erosion of which has contributed to the accumu- 

 lation of fossil-bearing alluvium within the troughs. 



Only a few of the more important investigations and explorations of 

 geologic significance which should be attempted by vertebrate paleontolo- 

 gists in the immediate future can be mentioned. 



1. The contemporaneity of mammals and dinosaurs in South America 

 should be investigated and an effort made to ascertain more about the 

 affinities of the dinosaurs associated with the Xotostylops fauna. The 

 significance of the resemblance of the Xotostylops fauna to that of the 

 Puerco can only be determined by greatly increased collections. The 

 occurrence of dinosaur-bearing beds above horizons affording mammal 

 bones is demonstrated conclusively by the photographs published by San- 

 tiago Roth. Until the age of the ^otostylops fauna is settled we are not 

 justified in separating the Mesozoic from the Tertiary on the basis of 

 dinosaurs alone. 



2. The vertebrate fauna of the Fort Union should be increased. Here 

 dinosaurs and Tertiary plants are said to be contemporaneous. At a 

 few localities the Torrejon mammal fauna has been found. It is desira- 

 ble to ascertain what the relationships of the horizons affording this 

 fauna may be to the dinosaur-bearing beds, and also whether the Puerco 

 fauna which underlies the Torrejon in the type locality in New Mexico 

 may be found elsewhere in areas now regarded as Fort Union. To some 

 extent the problem of the Notost3'^lops beds is duplicated here. 



3. The solution of the problems just mentioned necessitates a fuller 

 knowledge of the mammal faunas of the Cretaceous. The fragmentary 

 remains from the Morrison, Belly River, Judith, and Laramie are of 

 little assistance in deciding whether the mammals of the Notostylops 

 beds are, by any chance. Cretaceous in their affinities. 



4. A study of Pleistocene non-marine fossiliferous deposits in relation 

 to the glacial stages is much to be desired. The late Professor Calvin's 

 paper on the Aftonian mammal fauna was a step in the right direction. 

 Such investigations ma}^ properly be allied with prehistoric archeology. 

 In comparison with European workers, we have done almost nothing 

 with the problem of Pleistocene man in America. 



5. The correlation of marine with non-marine beds has already been 

 mentioned. The best efforts of all paleontologists should be concentrated 

 on this most important matter. 



