NO. 8 UPPER EOCENE ARTIODACTYLA — GAZIN 5 



formation on Leptotragulus which he considered as a synonym of the 

 invalid Parameryx. 



In the same year (1893) that Peterson first visited the Uinta Basin, 

 the American Museum had Wortman collecting in the Washakie 

 Basin. Wortman's work here was carried on further in 1895, and 

 then in 1906 Granger, accompanied by Osborn, renewed investigation 

 of these beds. The later Washakie expeditions, however, do not 

 appear to have contributed significantly to our understanding of upper 

 Eocene artiodactyls. 



Undoubtedly the most intensive exploration work in the Uinta was 

 that of later years by the Carnegie Museum, and Peterson's 191 9 

 study of the fauna was essentially the result of Douglass' collecting 

 in 1908 and 1909, and of his own in 1912. In this contribution Peter- 

 son added Hylomeryx, Sphenomeryx, and Mesomeryx to Wortman's 

 Bunomeryx, as representing the homacodonts, and described the large 

 agriochoerid Diplohunops, which from foot structure he believed to 

 be related to the European Diplohune. New species also were added 

 to Protoreodon, Protylopus, and Leptotragulus. Subsequent explora- 

 tion for the Carnegie Museum in the Uinta Basin over a number of 

 years has included particularly the collecting of J. LeRoy Kay and 

 John Clark as well as Peterson, and in 1929 resulted in discovery of 

 fossil materials in the relatively barren upper portion of the Uinta 

 sequence. The collections of 1929-1931 from these upper beds were 

 described by Peterson in 1931 as Oligocene in age, and the upper red 

 facies was named the Duchesne formation, later corrected to Duchesne 

 River as the earlier name was found to be preoccupied. At this time 

 Peterson named the homacodont Pentacemylus and the leptotragulid 

 Poabromylus, believing that the latter was a camelid. In a separate 

 paper that year he added Diplohunops uintensis and Diplohunops 

 ultimus to the growing list of agriochoerids from the Uinta beds. 

 Peterson's last study of the upper Eocene, which appeared in 1934 as 

 a posthumous paper, was largely concerned with the Duchesne River 

 artiodactyls and included descriptions of Mesagriochoerus primus, 

 Leptomeryx{?) minutus, and an unnamed species of Helohyus, all 

 three of which I am inclined to regard as incorrectly allocated. 



A final and detailed summary of the Duchesne River fauna was 

 made by Scott in 1945, and in this he largely retained Peterson's 

 identifications and taxonomic arrangement. Scott, like Peterson, be- 

 lieved the age of these beds to be Oligocene, a conclusion not generally 

 accepted by contemporary and later workers. Unfortunately, for a 

 proper understanding of the sequence and age relationships of the 

 forms involved, Scott listed as in a single fauna all the forms involved 



