Report of a reconnaissance from Carroll, Montana Territory, on the upper Missouri, to the Yellowstone National Park, and return, made in the summer of 1875 . extends out for some distance from it, covering up all sedimentary strata beneath it. Atc rises a second complementary hill of trachyte, and lying between these two aud limiting theprairie in this direction is an imposing limestone wall. This is worth mentioning, for it is so conspicuous an object as to be distinctly visible in clear weather at a distance of fifty miles to thesouth. The mountains seem from such a point to have a continuou
Report of a reconnaissance from Carroll, Montana Territory, on the upper Missouri, to the Yellowstone National Park, and return, made in the summer of 1875 . extends out for some distance from it, covering up all sedimentary strata beneath it. Atc rises a second complementary hill of trachyte, and lying between these two aud limiting theprairie in this direction is an imposing limestone wall. This is worth mentioning, for it is so conspicuous an object as to be distinctly visible in clear weather at a distance of fifty miles to thesouth. The mountains seem from such a point to have a continuous white girdle running aroundthem. This is due to the limestone and to its continuation east and west in the range; the abruptwall of trachyte also continues this girdle where the limestone is interrupted. The limestonewall shows no stratification, but its face has a steep dip south 70°, and, in character as well as inresult of weathering, resembles the Carboniferous limestone so often described. TO YELLOWSTONE NATIONAL PARK. 129 Fig. 14. , . Littlii Roclcy Mountains. ,„v,„*,. n-achytc IVacJii/lf. ?*?^/, Vs?=; «i\„; ? I,*,,,!**!,/;:,.-, ;;;. -_ t Gravity meadnw. .^i Siiridstinw -t \ At the west eud of this limestone wall, a little canon opeus out, showing the coasiderable thick-ness of the limestone. Lower layers afforded the following fossils, of which a list is here given, withremarks made upon them by Mr. Whitfield : 1. Olauoonome, si).l—Too indistinct for specific determination. 2. ProduGtus, sp. 1— This has a feature (elongated depressions) which is seldom seen in rocks above the Chemung of New York or Waverly sandstone of Burlington, Iowa. 3. Chonetes, sp. 1—Resembles G. granuUfera, Owen; also very like C. subumbona, M. & W. 4. Chonetes, sp.—Thismaypossibly be only a variety of the preceding, with which ; but had I seen only this fossil, I should have thought it Lower Silurian. 5. Spirifera centronata, Winch. In regard to these
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