June, 1912. New Titanotheres — Riggs. 23 



Sthenodectes incisivum and Amynodon intermedins were recorded. The 

 remaining seventy-five feet below the Amynodon Sandstone consist 

 of light gray or greenish clays little indurated and weathering in the 

 form of typical bad lands. These contain a varied fossil fauna but 

 having been exploited by earlier collectors, little attention was given 

 to them. However, specimens of Uintatherium (?), Stylinodon sp., 

 Amynodon intermedins and Protylopus were recorded. Capping this as 

 the "rim-rock" of the basin is the massive Amynodon Sandstone before 

 mentioned. It reaches in places a thickness of twenty feet, thins out 

 and sometimes disappears entirely but is replaced again by a similar 

 ledge at approximately the same level. These ledges are perhaps the 

 richest in vertebrate fossils of any horizon noted. Amynodon and 

 Crocodilus are common; Protelotherium uintense also was found. 



RANGE AND OCCURRENCE OF FOSSILS 



Some observations upon the range and occurrence of fossil mammals 

 in the Lower Uintah formations are worthy of mention. A careful 

 record was kept of the exact geological horizon of every specimen 

 collected. Attention was also given to the character of the formations 

 in which the various fossils occur, their sequence and the association 

 with plant and invertebrate fossils, in order to throw any possible light 

 upon the condition of deposition or the habits of the animal. The 

 geological distribution as indicated in Figs. 1 and 2 is based entirely upon 

 the collection made by this expedition. With a few exceptions the data 

 are based upon material sufficiently complete to be preserved as museum 

 specimens and accurately identified. In no case was a record made 

 from fragments not in situ. The Lower Metarhinus Zone is indicated 

 as relatively barren. 



Five genera of mammals have been reported* by Osborn from the 

 entire Horizon A. Mr. Peterson, who made the collection, has 

 assured the writer that the type specimens of Metarhinus fluviatilis 

 and Sphenocoelus uintensis came from the lowermost levels of that 

 horizon. In the lower zone typical fossil -bearing ledges occur, but 

 much less frequently than in the upper. A number of ledges ex- 

 amined by our party proved quite barren. In the upper strata frag- 

 ments of turtle shell were noted. It is quite probable that somewhere 

 in these channel deposits fossil-bearing "pockets" may be discovered. 

 Upon such discoveries rests the hope of further light upon the fauna 

 of the Lower Metarhinus Zone. The sandy shales such as make up the 

 larger part of this series do not offer conditions favorable for the preser- 



* Bull. Am. Mus., Vol. VII, p. 75. 



