130 GEOLOGICAL SURVEY OF THE TERRITORIES. 



the smaller animals are still quite abundant, especially in the valleys of 

 the small streams, where they flow down through the mountains ; Elk 

 Mountain and Sheephead Mountain have always been noted localities for 

 these animals. 



The traveler will have his attention called to Carmichael's Cut, an 

 excavation through the arenaceous clays and sandstones of the upper 

 cretaceous deposit, which has become noted for the wonderful fossils 

 found there. Baculites, Ammonites, Inocerami, and a great variety of 

 marine shells, glistening with the iridescent hue of mother-of-pearl, are 

 found in aggregated masses, as if this had been a portion of the creta- 

 ceous sea. Farther on, at Miser Station, these beautiful fossils occur 

 again in the greatest abundance, and thousands of them have been gath- 

 ered and carried away by curiosity-seekers. Near Medicine Bow the 

 lower cretaceous clays prevail, and in the hills bordering the Medicine 

 Bow Creek a large singularly tuberculated ammonite is found associated 

 with a species of scaphites or boat-shaped shell, looking very much like 

 a large worm coiled up, and hence its name, S. Larvceformis. These 

 shells have received all sorts of names in the country, and the most 

 wonderful tales are related of petrified snakes, &c. 



All over this Rocky Mountain region, from the Arctic Circle to the 

 Isthmus of Darien, these remarkable marine shells are found, and in 

 some instances upon the summits of the loftiest ranges. 



The valleys of the Upper Missouri and Yellowstone Rivers have 

 already yielded nearly four hundred varieties of these sea-shells. We 

 have, therefore, the most ample evidence that in past geological times 

 the great ocean rolled all over the area now occupied by the mountain 

 ranges. 



After passing Cooper's Creek Station we come into the black clays of 

 the lower cretaceous, and the appearance of the country becomes 

 dreary and sterile in the extreme. The waters are alkaline, and there 

 is no timber along the creeks except stinted willows, and very little 

 grass or vegetation except chenopodiaceous shrubs, which are fond of 

 this alkaline soil. As far as the eye can reach nothing can be seen but 

 these somber, plastic clays. The surface also presents the characteristic 

 monotonous appearance which is common wherever these clays prevail. 

 Six miles before reaching Como we come to an interesting quarry of 

 sandstone, from which the materials for the construction of the exten- 

 sive railroad buildings at Laramie City and Cheyenne are obtained. 

 The rock is gray, coarse, and friable, and one would suppose not durable 

 enough for such important structures, but it is easily wrought into any 

 determinate form. This is a locality to which I call the special attention 

 of the geologist as one in which there is an interesting problem to work 

 out, viz : What is the exact position of this sandstone in the geological 

 series 1 It is filled with fragments of vegetable impressions, with some- 

 times quite distinct deciduous leaves, much like those already noticed 

 in Chapter II as occurring at Blackbird Hill, on the Missouri River. 

 The leaves of the willow and poplar are quite distinct, reminding one 

 of those growing along our little streams at the present day, and yet 

 they are all of extinct species. These sandstones are local and seem to 

 have been deposited over a small area, inasmuch as they occur nowhere 

 else on the plains, so far as I have observed. 



The black shales filled with remains of fishes and marine shells occur 

 above and below the sandstones, showing very clearly that they are of 

 lower cretaceous age. Still it would be a matter of interest to attempt 

 the construction of the physical conditions which were necessary in 

 those old cretaceous times, myriads of ages ago, for the ocean waters to 



