0. C. Marsh— Geology of the Uintah Mountains. 193 



eitlier side, still nearly horizontal, and in places beautifully 

 variegated by layers of light green clays, alternating with others 

 of various shades of brown. In addition to the numerous ver- 

 tebrate remains, a few fresh -water mollusca were observed, espe- 

 cially on Henry's Fork, the more common being Planorhis spec- 

 iabifis Meek, abundant in some of the harder layers, and Helix 

 altispira Meek. Farther down the stream, and about fifteen 

 miles from its mouth, several seams of lignite were noticed on the 

 right bank. In the intervening shale were some tliin hiyors ot 

 black hornstone, and others containing great nuinln rs ot shells, 

 principally Unios and Melanias. One of \\\v lattfr was ai'i'ar- 

 ently identical with the species describetl by Pn. lessor Hall in 

 Fremont's Report (page 308), as Cerithium iexerum, which, how- 

 ever, with its associate fossils, is clearly a fresh -water typa 

 A few feet under the lignite, were layers of shale full of Cypris, 

 with here and there cycloidal fish-scales and coprolites. 



A few miles below, a red sandstone dipping slightly to the 

 N.W. makes its appearance on the left bank, beneath the light- 

 colored Tertiary deposits, and farther down, curves upward into 

 a sharp ridge, of highly inclined strata, through wliich the 

 stream has obliquely cut its way. On the southern side, these 

 beds fonn a wall of sandstone, nearly perpendicular, resem- 

 bling stronglv the famous " Teufels Mauer"' in the Hartz. This 

 ridge, one of the typical foot-hills of the Uintah range, makes 

 a sigmoid curve along the base of the mountains, from which 

 its strata dip away at various angles. The different colored 

 sandstones which compose it are evidently of Mesozoic age, 

 and probably Cretaceous, as they have below them, farther 

 down the stream, calcareous beds containing undoubted Jurassic 

 fossila These are in turn underlaid by sandstones, which are 

 probably Triassic, and these again by well marked Carboniferous 

 strata, near the junction of Henry's Fork with the Green River. 



At this point the Green River leaves the great Tertiary busm 

 which it drains for 200 miles or more, and cuts through the 

 eastern Uintah Mountains by a succession of narrow canons, 

 with walls of older rocks, whose exact age can be determined 

 only by a systematic study. In continuing our course down 

 the east side of the river, we passed over several high ndges, 

 composed mainly of hard reddish sandstones and quartzites, 

 J^ore or less metamorphosed, and apparently without fossila 

 The general inclination of these beds, which are of great thick- 

 ness, was to the N.E., or away from the Uintah mountain nu- 

 cleus, but the dip varied greatly at different points. Ripple- 

 niarks and oblique lamination showed them to be shallow water 

 •deposits, and a subsequent examination of apparently a portion 

 01 the same series on the western side of the river, rendered it 

 probable that a part of them at least are of Silurian age. 



