220 Annals of the Carnegie Museum. 



masses of red rock, which has often been broken into fragments and 

 recemented. This "baked rock" at first sight looks much like 

 lava, and was often mistaken for it by early travellers ; but volcanic 

 action and volcanic products are entirely absent from this region. 



At Medora. 



We made a stop at Medora and had an opportunity to examine the 

 rocks more carefully and at closer range. Being anxious to explore 

 the hills, we arose early and walked a short distance to the bluffs just 

 east of the town. Not only did the rocks and bluffs appear strange 

 to us, but some of the living plants were unfamiliar. We noticed sev- 

 eral species of Leguminosae and an evening primrose in bloom. The 

 most conspicuous flower was that of a species of Mentzelia. On the 

 fiat the sage-brush thrived in places, while on the sides of the bluffs 

 Rhus trilobata was the principal shrub. 



The beds are usually soft, except where they have been baked ; yet 

 there are some harder layers and lenses of flinty texture. The strata 

 consist of soft shales, incoherent dust or dirt, and laminated and thick- 

 layered sandstones. In the shales, sandstones, and even in the lenses 

 of hard compact rock, we found impressions of plants, especially roots 

 of Eqiiiseium and leaves of deciduous trees. In one or two places we 

 saw shells of fresh- water moUusca — gasteropods and Unios. 



Just above Medora the river is quite rapidly cutting and undermin- 

 ing the bluff's on the eastern side. The banks next to the river for fifty 

 or seventy-five feet are steep, and above the steep bank the slope is 

 covered with masses of gray rock, which have tumbled down from 

 above. Some of these blocks are full of the impressions of roots and 

 tubers of Equisetum. 



Medora stands on an alluvial flat. In places rains and melting 

 snows have cut ravines into the recent deposits of the river bottom. 

 These dirt-beds are either massive, banded, or locally imperfectly strati- 

 fied. On the west side of the river between the railroad track and 

 the residence built by Marquis de Mores, on a hill overlooking the 

 Little Missouri River, is a deep steep-sided ravine, which has been 

 carved in the alluvial deposits from the river backward to the side of 

 the flat next to the hills. In the steep sides of this ravine, buried in 

 the deposits of the river bottom fifteen or twenty feet below the top of 

 the bank, the skull and bones of a bison were found. In the bottom 

 of the cut near the head of the ravine the Fort Union beds are ex- 

 posed, and in them are many fossil leaves. 



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