356 F. B. Loomis — Origin of the Wasatch Deposits. 



Art. XXXIV. — Origin of the Wasatch Deposits ; by F. B 



Loomis. 



While cataloguing the collection from the Wasatch beds of 

 the Big Basin, secured by the Amherst expedition of 1904, the 

 predominance of terrestrial forms raised the question as to the 

 mode of deposit of these strata. It has been the general impres- 

 sion that they represent an ancient lake bottom,* and this view 

 has been adopted in text-books, except in Chamberlin and Salis- 

 bury's Geology, where exposure to the air is suggested. 

 Recent studies of epicontinental modes of deposition have 

 made easy their application to the case imhand. Two means 

 of approach are available : (1) By an analysis of the fauna, 

 and (2) by a study of the section. Both these methods will be 

 employed. 



In the following table the fauna is carefully arranged, the 

 groups being given according to their probable terrestrial, 

 arboreal, amphibious and aquatic habits. The collections are 

 from two levels on Tatman Mountain and one level in Buffalo 

 Basin. The upper Tatman Mountain horizon is about 100 feet 

 above the lower, while both Tatman Mountain levels are con- 

 siderably below the Buffalo Basin level. 



Lower Higher 



level level 



Tatman Tatman Buffalo 



Mt. Mt. Basin Total 

 Aerial forms : 



Gallinuloides prentici 3 .. .. 3 



Arboreal forms : 



•Pelycodus frugivorus 2 26 3 



" tutus ... . . 2 



Anaptornorpha minutus .... 1 .. 34 



Terrestrial Forms : 

 Gamivora : 



Stypolophus whitiae 1 5 



" sp. ... 1 4 



\iverravus protenus 4 1 



" leptomylus ^ . . 2 1 



" altidens .. __ 1 



Oxyaena lupina 2 3 __ • 



Uintacyon sp. ? 3 .. 



Anaeodon ursidens 1 4 



" sp. ?... 1 2 .. 36 



* Wortman, 1892, Bull. Amer. Mus. Nat. Hist., vol. iv, p. 135. 



