NEW OR LITTLE KNOWN TITANOTHERES FROM THE 

 LOWER UINTAH FORMATIONS 



WITH NOTES ON THE STRATIGRAPHY AND DISTRIBUTION OF FOSSILS 



BY E. S. RIGGS 



In the summer of 1910 the writer was authorized by the Museum 

 to make an expedition into the Uintah Basin of northeastern Utah for 

 the purpose of collecting vertebrate fossils. Accordingly, a party con- 

 sisting of Mr. J. B. Abbott of the Museum and Mr. M. G. Mehl, a 

 student of the University of Chicago, was organized. This party pro- 

 ceeded by way of Dragon, Utah, thence overland to Vernal, where the 

 necessary equipment and supplies were obtained. A camp was then 

 established near Well 2 at the foot of Coyote Basin. Six weeks were 

 spent in working the exposures within driving distance of this camp, 

 after which a "dry camp" was pitched at the margin of White River 

 Canyon. From this base work was continued in the exposures of the 

 canyon wall during the remainder of the summer. Great difficulties 

 were experienced on account of the scarcity of water and feed for horses, 

 and on account of the extreme hardness of the formation. In excavat- 

 ing fossils the use of drills and blasting materials was often necessary. 



The result of this expedition was a large collection of skulls, jaws, 

 and two partial skeletons belonging to the family Titanotheridce. This 

 family is represented in the collection by the genera Mesatirhinus, 

 Metarhinus, Dolichorhinus, Rhadinorhinus and Sthenodectes. A special 

 interest attaches to representatives of the first four genera because of 

 the more complete representation of their Uintah species and the inter- 

 relationship of the genera which the collection brings out. Many of 

 these species were obtained from a lower fossil-bearing horizon which 

 has hitherto been little explored. Other genera represented in the 

 collection are Eobasileus, Uintatherium, Amynodon, Triplopus, Pro- 

 telotherium, Protyhpus, Stylinodon, Mesonyx and Harpagalestes. 



The genus Rhadinorhinus is new, Mesatirhinus and Stylinodon are 

 for the first time reported from the Uintah formations, and Eobasileus 

 is first reported from skulls capable of identification. 



STRATIGRAHPY 



The Uintah formations, or " Uintah Group," were primarily sub- 

 divided by the U. S. Geological Survey upon an evident change in the 

 lithological structure of the beds. This division separated the lower 



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