4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I44 



former scientific assistant, was particularly helpful in locating speci- 

 mens and arranging for loan of materials. 



As in previous years I was assisted in the field during the more 

 recent investigations of 1953 to 1959 by Franklin L, Pearce, chief 

 of our laboratory of vertebrate paleontology, with the additional help 

 of Theodore B. Ruhoff in 1956. In 1953 George Pipiringos of the 

 U. S. Geological Survey kindly conducted us to various fossil locali- 

 ties that he and Dr. R. W. Brown had located the year before. These 

 included the Red Desert locality east of Steamboat Mountain and 

 sites near Tipton Butte, from which collections had been sent to me 

 for identification and report in 1952, but too late for my paper of 

 that year. 



Most important to the value of this study are the incomparable 

 pencil drawings prepared for the accompanying plates by Lawrence 

 B. Isham, staff illustrator for the Department of Geology in the 

 U. S. National Museum. 



GEOLOGIC RELATIONS 



Important new information on the geologic ages and sequence of 

 early Tertiary formations in the southwestern part of Wyoming, 

 particularly in the Fossil Basin and adjacent parts of Utah, necessitates 

 a restatement of geologic relations, modifying the summary and 

 definitions of usage presented in 1952. Much of this relates to demon- 

 stration by Tracey and Oriel (1959) that the Fowkes formation is 

 stratigraphically higher than the Knight and a revision by Bradley 

 (1959) of the nomenclature and relationships of members of the 

 Green River formation in the Wyoming area. Further information 

 on ages of various horizons in this sequence likewise calls for addi- 

 tional discussion. 



Evanston formation. — The earliest formation in the Fossil Basin 

 including strata of Tertiary age is the Evanston. Fossil mammal ma- 

 terials encountered (Gazin, 1956a) near Fossil Station on the Union 

 Pacific Railway demonstrate that the uppermost beds of this unit are 

 Tiffanian Paleocene in age. Tracey and Oriel (1959) found cera- 

 topsian dinosaur materials in the lower part of the formation, show- 

 ing that beds as old as upper Cretaceous are also included. 



Wasatch formation. — The original definition of Wasatch by Hayden 

 (1869) can only be interpreted as including the section of essentially 

 reddish or variegated beds extending from near Carter, Wyo., to the 

 "Narrows" of Echo Canyon in Utah. Moreover, Hayden's selection 

 of the term "Wasatch" cannot be interpreted as implying a type sec- 



