OF THE UPPER MISSOURI, 7d 
In the vicinity of Bijoux hills this formation seems to have been much depressed or to 
have suffered denudation prior to the deposition of No. 4, not more than twenty or thirty 
feet being exposed above the water-level. About twenty miles above this point a thick- 
ness of sixty or seventy feet is seen. Near the mouth of White river I found in this bed a 
large mass of calcareous spar, six feet-in length and eighteen inches in thickness, also 
nodules of limestone formed of concentric coats, which is, I think, the same described by 
Nicollet as “ cylindrical limestone resembling Arragonite.” 
Although so well developed and covering so wide an area on the Missouri, the middle 
and upper portions at least, of this rock can never be made useful for building purposes. 
Quite soft and friable in place, when detached it absorbs moisture rapidly and crumbles in 
pieces. Being a rich calcareous marl, it may be used at some future time as a fertilizer. 
The fossils of this formation, although belonging to few species, so far as yet known, are 
numerous in individuals, A species of oyster (O. congesta) is found in great quantities 
throughout the bed, and in localities Zroceramus problematicus is abundant. Fish remains, 
though consisting mostly of scales and obscure fragments, are disseminated throughout the 
deposit, several species of which have already been identified and described by Dr. Leidy. 
Near First Cedar island a very singular bed makes its appearance, superimposed on No. 
3, Which may be considered as probably forming an upper member of this formation, It 
extends up the Missouri about eighty miles to a point near the Great Bend; lithologically 
it is a dull black unctuous clay, entirely destitute of any grit, and does not effervesce with 
an acid. It contains some carbonaceous matter, great quantities of selenite in crystals, in 
thin lamin, and in thick rhomboidal masses. In a number of localities I noticed fish 
remains, but no other organic bodies. In several places the carbonaceous matter of this 
bed has been ignited, producing heat enough to give to the surrounding strata a brick-red 
color, and the slabs of clays thus affected by the heat give a ringing sound under a blow 
of the hammer. Ten miles below the mouth of White river this rock has been subjected 
to a considerable degree of heat for several yards, so that the surrounding strata present an 
appearance similar to those which have been affected by the burning of the lignite beds on 
the Yellowstone. ‘The superincumbent beds have from this cause fallen in some instances 
fifteen or twenty feet below their original position. Mr. Nicollet, in his interesting report 
on this region, examined these phenomena with great care, and I cannot do better than to 
quote his explanation of them: “ ‘These pseudo-volcanic phenomena may be compared 
with those described as occurring in other portions of the globe under the name of terrains 
ardens, although they are not here accompanied by the emission of flames. They are 
evidently due to the decomposition, by the percolation of atmospheric waters to them, of 
beds of pyrites, which, reacting on the combustible materials, such as lignites and other 
substances of a vegetable nature in their vicinity, give rise to spontaneous combustion, 
