NATURAL SCIENCES OF PHILADELPHIA. 
47 
It is, perhaps, scarcely necessary for us to remark that the presence of Am- 
monites and BelemniteSj in the rocks above alluded to, aside from the other or- 
ganic remains, is alone satisfactory evidence that they do not belong to the 
Triassic epoch. It is true the bed C is not known to contain either Belemniies 
or Ammonites^ but so many of the same forms associated with these fossils iu 
the beds above, range down into the bed C, that unless it be the lowest stratum 
of yellowish gray sandstone at its base, there appears to be little reason for sus- 
pecting that it may belong to another system of rocks. In regard to this lowest 
stratum of formation C, we would state that the fossils contained in it are casts 
in a bad state of preservation, but as near as we have been able to determine, 
some of them appear to belong to types occurring in the beds above; we, there- 
fore, for the present, place it provisionally as a part of the group composing 
formation C; but it is possible future investigations may bring to light facts 
that may prove it to belong to an older series, though it evidently is not Car- 
boniferous, nor Permian. 
Carboniferous Rocks of the Black Hills. 
As may be seen by consulting the foregoing general section of the formations 
seen in and around the Black Hills, the rocks we regard as of Jurassic age, 
repose in that region upon a group of deposits, the larger portion, at least, 
of which clearly belong to the Carboniferous epoch. 
"We would, however, just here remark before entering upon the discussion of 
the Carboniferous formations of the Black Hills, that near the south-eastern 
base of these hills some loose masses of a cherty rock were seen, on more than 
one occasion, under circumstances indicating that the stratum from which they 
were derived holds a position between the base of the bed C and the bed D of 
the section. Yet as these cherty masses were no where actually seen in place, 
we have not given them a position in the Black Hills' section, though there can, 
scarcely be a doubt that they belong to it. The fossils they contain, or at any 
rate several of them, are identical with species occurring in a formation in 
north-eastern Kansas, now known to be of Permian age. 
The first formation in the descending order of the foregoing section we are 
inclined to place, (at least provisionally) in the Carboniferous system, is the bed 
D, which is composed of a brick-red fine silicious or argillaceous, slightly gritty 
material, effervescing very feebly in acids. Although from a hundred to one 
hundred and fifty feet in thickness, no vestiges of any kind of organic remains 
were seen in any part of this bed; but it was always found to be characterized 
by large quantities of gypsum, in the form of seams, layers, and large beds or 
irregular masses. 
Beneath the foregoing bed we have a bluish and reddish gray, somewhat 
gritty limestone (E of the section), varying from 10 to 50 feet in thickness, anci 
containing fossils, resembling coal measure forms. The collections from thip 
rock consist of a small smooth spirifer^ broader and more compressed than IS. 
lineatus, but otherwise somewhat similar, two or three species of 3Iacrocheiluy, 
two small species of rieuroiotnaria, and one or two species of Bellerophon, all in 
a rather bad state of preservation, but showing very satisfactorily their generic 
characters. 
and was necessarily based upon very erroneoua views in regard to its topography. In 
addition to this, we had found the immense area represented by him as New Red Sand- 
stone, in the upper Missouri country, almost entirely made up of Tertiary and Cretaceous 
deposits ; while not a single Jurassic or Triassic fosail had ever been found throughout 
the whole country. 
Since the position of the Black Hills has been determined by Lieut. Warren, we now 
know the area occupied by the Jurassic belt Mr. Marcou intended to place east of these 
hills, actually lies rather on the west of their middle portion, and does probably cover 
some surface occupied by the formations we regarded as Jurassic. 
By these remarks we do not wish to be understood as intimating that a geologist is re- 
sponsible for errors into which he may be led by incorrect topographical maps ; nor do 
we wish to withhold from Mr. Marcou the credit justly due him for having first suggested 
the existence of Jnrassic rocks in this region. 
1858.] 
