6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 128 



in the study, and it is noted that such forms as, for example, Camelo- 

 don arapahoviiis, and possibly others known to be from the Uinta 

 equivalent in the Beaver Divide area, are included with Randlett 

 "Mesagriochoerus" primus, Lapoint Poabromylus kayi, and Lepto- 

 meryx(?) minutus (this is Simimeryx), together with Oligocene 

 Brachyhyops Wyoming ensis. 



Various institutions have paid visits to the Uinta and Washakie 

 Basins in late years, and mention may be made of that conducted by 

 the writer for the Smithsonian Institution in 1938 which led to the 

 present study. We were indeed fortunate in locating a site which 

 produced an excellent series of specimens representing the smaller 

 Artiodactyla of the Myton or C horizon. The work of Princeton 

 University in recent years has been referred to, and a collection 

 obtained by a group from Harvard University in 1940 was also made 

 available for this study, but unfortunately much of the latter material 

 has yet to be prepared. 



GEOGRAPHIC AND GEOLOGIC OCCURRENCE 



There are essentially but five general areas where mammal-bearing 

 deposits of upper Eocene age are exposed, and all these have pro- 

 duced notable fossil remains of Artiodactyla. Listed in order of 

 importance, they are the Uinta Basin in northeastern Utah, the 

 Washakie Basin in southern Wyoming and adjacent Colorado, the 

 Wind River Basin in central Wyoming, the area in which the Sespe 

 formation is distributed in southern California, and Sage Creek, 

 Montana. By far the most significant area, and that from which re- 

 mains of most of the known forms have been obtained, is the Uinta 

 Basin. It is here that we have the most nearly complete stratigraphic 

 sequence known for the continental upper Eocene, a sequence that 

 is used rather generally as a standard of reference for studies else- 

 where. Two formations are recognized, the lower or Uinta, inter- 

 fingering below with the Green River beds, and the upper or Duchesne 

 River, based essentially on a facies change from that of the Uinta 

 resulting from a change in source of sediments. Laterally, this facies 

 change transgresses time boundaries, and hence cannot be relied on 

 as limiting horizons or ages except in closely adjacent sections. The 

 Uinta formation is divided into three parts lettered A to C ; or into 

 two parts : Wagonhound, including A and B, and Myton, comprising 

 C. The Duchesne River or red facies has been likewise divided into 

 three members. Kay has named these Randlett, Halfway, and Lapoint 

 in ascending order. Remains of Artiodactyla have been obtained from 

 all except Uinta A, with the bulk of the material coming from B and 



