OF THE UPPER MISSOURI. 55 
together with apparently the same Monotis, so often mentioned below. In 12, we also 
have added a small Spirifer, similar to S. lineatus, but perhaps more nearly allied to the 
Permian species Martinia Clannyana, King. 
The succeeding bed above, No. 11, appears also to contain a mingling of Permian with 
Coal measure forms, for we have in it the following Permian types, viz.: Myalina very 
similar to M. squamosa, Pleurophorus ? subcuneata, Bakevellia parca, and Monotis Hawni, 
along with a Euomphalus near E. rugosus, the same gibbous Spirigera, similar to S. sub- 
tilita, Orthisina umbraculum ?, and O. Shumardiana. 
On passing into the next division above, No. 10, we find we have lost sight of all the 
characteristic Carboniferous forms, unless the Spirigera mentioned in some of the beds 
below be regarded as only a variety of S. subtilita, from which, however, we think it 
specifically distinct ; for with this exception, nearly all the fossils seen by us in this divi- 
sion are such as would be regarded as Permian types. Although the number of species. 
found by us in No. 10 is not great, individual specimens are often numerous, Above this 
horizon we saw no more fossils through a great thickness of various colored clays, clay- 
stones, &c., until ascending to the Cretaceous sandstones crowning the Smoky hills, 
If we do not admit the existence in this region of an intermediate group of rocks, con- 
necting by slight gradations the Permian above with the Coal measures below, and must 
draw a line somewhere, below which all is to be regarded as Carboniferous, and all above 
as Permian, we should certainly, upon paleontological principles alone, carry this line up 
as far as the top of division No. 11. The passage from the Carboniferous to the strata 
containing Permian types, however, is so gradual here, that it seems to us no one, under- 
taking to classify these rocks without any knowledge of the classification adopted in the 
Old World, would have separated them into distinct systems, either upon lithological or 
paleontological grounds, especially as they are not, so far as our knowledge extends, sepa- 
rated by any discordance of stratification, or other physical break.* Indeed, the fact that 
some of the Permian types occurring in No. 10, were first introduced in beds below this, 
containing many Carboniferous species, would seem to indicate that even No. 10 may 
possibly have been deposited just before the close of a period of transition from the condi- 
tions of the Carboniferous, to those of the Permian epoch. 
The apparent absence of fossils in the beds above No. 10, renders it impossible, with 
our present information, to determine with certainty the upper limits of the series contain- 
* We have been informed by Dr. J. G. Norwood, former State Geologist of Illinois, that the rocks in that State, 
referred by him and others to the same epoch as the Kansas Permian beds, rest unconformably upon the 
measures, This, however, would be impossible in Kansas, since no disturbances of the strata occurred there, until 
after the close of the Cretaceous era, which would, of course, not only cause the Cretaceous and Carboniferous, but 
all intermediate beds, to dip at the same angle. 
