June, 1912. New Titanotheres — Riggs. 19 



deposit of Gilsonite^ which cuts deep into the canyon wall three miles 

 below the mouth of Evacuation Creek and extends some miles to the 

 northwestward offers a convenient point for making a section. Actual 

 measurements were not made, but the contour lines of the U. S. Survey 

 maps made it possible to estimate with some degree of accuracy the 

 vertical dimensions. Figure 1, representing this section, is based upon 

 these estimates. 



Lower Metarhinus Zone. The shaly gray, sandstones of lacus- 

 trine origin which have been more or less provisionally referred to the 

 Green River series* dip slightly below the bed of White River at this 

 point. Upon these shales, with no very evident line of demarcation, 

 lies the Uintah Series. The lower two hundred feet of this series is 

 largely made up of friable, sandy shales, interspersed with layers of 

 nodules and thin ledges of sandstone. Occasionally these shales are 

 interrupted by massive ledges of sandstone of limited extent. The 

 latter are usually coarse-grained, cross-bedded in places but in the 

 thicker ledges quite homogeneous. They vary in color from a light 

 gray in the thinner layers to dull brown in the weathered surfaces of 

 the more massive ledges. These shales weather in rather steep slopes, 

 marked by the horizontal outcroppings of nodular or sandy layers. 



Above the shales at this point lies a series of columnar sandstones 

 some three hundred feet in thickness. They weather in the form of 

 bold cliffs, standing out as buttresses along the canyon wall. (PI. IV.) 

 These sandstones consist of relatively thin ledges of fine-grained, 

 often calcareous, sand varying somewhat in hardness and presenting 

 rugged bandings in the face of the cliff. The color is slightly more 

 grayish than the underlying shales but brown predominates. 



This lower five hundred feet of the Uintah Formation is compara- 

 tively barren of fossils. Some days' search in the vicinity of this section 

 revealed only occasional fragments of turtle shells. Mammals have 

 been found in these measures at other points along White River. The 

 type specimens of Metarhinus and of Sphenocoelus are said to have been 

 collected from the lower levels. The first has never been duplicated, 

 the second is represented by a fragment. While the occurrence of 

 these two genera in the lower measures is a matter of record, the rarity 

 of individual representatives, as well as the small number of forms found 

 in this horizon, may justify its being designated as relatively barren. 



Upper Metarhinus Zone. The succeeding four hundred feet is 

 made up chiefly of massive ledges of sandstone alternating with layers 

 of sandy shales or indurated clays. The sandstones vary in thickness 

 from five to thirty feet. They are of limited extent, usually playing 



* White, Op. cit. ; Scudder, Tert. Insects. 



