22 Field Museum of Natural History — Geology, Vol. IV. 



Five miles up the canyon from the line of this section a single ledge 

 (PI. V, Fig. i) a half-mile in extent yielded so many specimens of this 

 genus as to be designated by our collectors as the Metarhinus Sand- 

 stone. However, six other genera of mammals, one of crocodile and 

 various turtles are recorded from these beds. 



The term "Telmatherium megarhinum Beds," originally applied* 

 to this series, being no longer applicablef , it is here proposed to desig- 

 nate the series as the Metarhinus Beds, in honor of the form, which was 

 first described from them and is still their most characteristic fossil. 

 The beds may be further divided into a Lower and an Upper Metar- 

 hinus Zone as indicated in Figure i. 



Amynodon Beds. Above the Metarhinus Beds, or Horizon A, lies 

 a series of three hundred feet of shales and clays including occasional 

 ledges of fluviatile sandstone. They are best represented some five 

 miles farther up White River from the last section. At this point the 

 formation is exposed in the more open country in a series of eroded 

 ledges dipping to the northwestward at an angle of two or three degrees. 

 Gilsonite Vein No. 2, which extends several miles in a northwesterly di- 

 rection from the canyon's northern edge, may be taken as the basis of the 

 section (Fig. 2). This vein is marked by a series of mines and prospect 

 holes easily recognized. The section extends from the canyon rim to the 

 mesa bordering Coyote Basin on the northward. This includes sub- 

 stantially the same vertical series as Horizon B of Peterson and Osborn 

 so far as the writer has been able to interpret them. 



These beds are composed of sandy shales and brilliantly colored 

 clays with occasional ledges of sandstone and included lenses of more 

 limited extent. The series is capped by a massive ledge which appears 

 at the brow of the mesa bounding Coyote Basin on the northwest. 

 This may fittingly be designated as the Amynodon Sandstone. 



Between the uppermost ledge of the Metarhinus Beds and the 

 Amynodon Sandstone lie a series of clays and lenticular sandstones of 

 variable character. The Metarhinus Sandstones are succeeded by one 

 hundred feet of bluish or grayish shales including thin ledges of sand- 

 stone. These are overlain by forty feet or more of homogeneous fine 

 red clays, capped by a ledge of sandstone five or six feet in thickness. 

 Then come fifty feet of dark grayish clays including lenticular sand- 

 stones of rather coarse-grained, ferruginous character. These sands 

 weather in slopes quite as flat as the clays in which they are included. 

 They are rich in mammalian fossils, of which Dolichorhinus longiceps, 



* Bull. Am. Mus., Vol. VII, p. 95. 



t The specimen alluded to was later made the type of Metarhinus fluviatilis, see 

 Bull. Am. Mus., Vol. XXIV, p. 609. 



