DESCRIPTION OF REMAINS OF MAMMALS FROM THE TERTIARY 

 FORMATION OF SWEETWATER RIVER, WYOMING. 



A small collection of fossils, consisting of the remains of mammals, was 

 obtained, during Professor Hay den's expedition of 1870, on Sweetwater 

 River, eighteen miles west of Devil's Gate, Wyoming. 



Professor Hayden, in his Preliminary Report of the Geological Survey 

 of Wyoming, 1871, page 32, in relation to the locality whence the fossils 

 were obtained, makes the following remarks : " Near Cloven Peak, fifteen 

 miles west of Devil's Gate, there are some bluff-banks on the south side 

 of the Sweetwater, about one hundred feet high, which indicate the exist- 

 ence of quite modern Tertiary beds, like those on the "Niobrara River. 

 They are composed of indurated sands and marls of a light-gray or cream 

 color, and are in appearance precisely like those seen on the Laramie River, 

 and many other places, which I have usually regarded as of the Pliocene age. 

 Still farther to the westward are numerous exposures of these beds, which 

 are weathered into the usual fortification-like forms, and scattered around 

 their base are large numbers of remains of extinct mammals and turtles, 

 apparently identical with those found on the Niobrara.. They occur in the 

 same beautiful state of preservation.'' 



Professor 'Hay den's view of the age of the formation is confirmed by the 

 zoological character of the fossils, which are nearly related with those from 

 the Pliocene Tertiary sands of the Niobrara River, and are, without doubt, 

 of a much more recent date than those of the Bridger beds. 



The specimens submitted to my examination consist of fragments of jaws 

 with teeth, portions of the larger limb-bones, small bones of the feet, and a 

 few mutilated vertebrae. Most of them pertain to a species of Merycochoerus, 

 an animal nearly related to Oreodon. A few apparently belonged to a smaller 

 species, and several to a small equine animal. The others remain undeter- 

 mined for want of ready means of comparison. 



The fossils are all isolated specimens, which were picked up from the sur- 

 face of the ground. Usually they are perfectly free from adherent matrix. 

 They are white in appearance, and resemble recent bleached bones. They 



