NATURAL SCIENCES OF PHILADELPHIA, 
145 
lected from these rocks in the West, we did not refer to their supposed prior 
discovery in Pennsylvania and on the Atlantic coast, nor were we able to judge 
of the evidence of their existence in those localities, it being based, for the 
most part, upon the remains of Vertebrata, which are out of our line of inves- 
tigation. We also merely wished to announce the existence in the West of 
rocks which were on a parallel with the so-called Permian system of Europe.; 
without touching the great question whether or not there is actually a Permiar: 
system distinct from the Carboniferous. 
VI. Jurassic System. 
The Black Hills has, up to this time, afforded the most satisfactory evidence 
of the existence of this system in the West. It is there brought to the surface 
by the upheaval of the older rocks in the form of a belt or zone, five to fifteen 
miles in width, engirdling the principal axis of elevation. None of the organic 
remains already discovered, which are quite numerous in species, are known to 
be positively identical with those found in the same system in the old world, but 
they belong to the same genera, and many of the species are so closely allied to 
forms characteristic of the Jura of Europe, that we cannot now hesitate to admit 
this system into our series. I will here repeat the palaeontological evidence, 
which was read before the Academy in March last by Mr, Meek and myself, 
with such additional proof as we have been able to secure by our investigation 
of the undescribed fossils in the collection, up to the present time. 
1st. Pentacrinus asierisc7is,n. sp.,is so nearly like the Liassic P. scalaris, Gold- 
fuss, that it is with some hesitation we have regarded it as new. 
2d. Avicula (Monotis) tenuicosta, n. sp., is very closely related to M. suhstriata, 
of Munster, from the Lias. 
3d. Area {CucuUcea) inornaia^ n. sp., is very similar to G. Mumteri- (Zeiten,) 
also from the Lias. 
4th. Panopoea {Myacites) subellipiica, n. sp., is similar to the Liassic forms 
M. liasensis and M. Alduinimts, of Quensled. 
5th. Ammonites cordiformis, n. sp., is the same type as the Oolitic species 
A. cordatus, (Sowerby). 
6th. Belemnites densus, n. sp., is scarcely distinguishable from the Oolitic 
species B. ecceniricus, Biainville, if, indeed, it is really distinct. 
We have, also, in the collection from the Black Hills, a species of Hettangia, 
a genus not known to occur in the old world in formations newer than the Lias, 
and a Trigonia more nearly resembling Jurassic types than those of any other 
formation. 
Although it is not yet known to occupy a large geographical area in this 
country, we have indications that it will be found extensively developed ou. 
the eastern slope of the Rocky Mountains, from the northern part of British 
America to New Mexico. That it exists toward the head waters of the. 
Yellow Stone, around Panther and Big Horn Mountains, I cannot doubt. 
In the summer of 1854, while exploring the valley of the Yellowstone, a^- 
far as the mouth of the Big Horn River, 1 received, from intelligent traders, 
masses of gypsum precisely like that characterizing the Jurassic beds in the 
Black Hills. 
VII. Cretaceous System,* — Upper, Middle and Lower (including the 
Wbaldbn ?) 
The beds of sandstone impure lignite, &c., which we have hitherto dp- 
scribed as resting upon the Upper Carboniferous limestones, near Council 
*In a paper recently published by Maj. F. Hawn, in the St. Louis Acad. Sci , I observe 
he refers the whole of formation INo. 1 of the Nebraska section to the Trias; and alludes 
to the fact that Mr. Meek and I had referred it to the Lower Cretaceous. He also states, 
that he found in some of the lower beds included by us in this series in Kanzas, fosssif 
indicating relations rather to the Permian below than the Cretaceous above. 
In justice to Mr. Meek and myself, I would state, that these lower beds in Kanza? 
1848.J 11 
