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C. A. White on the Geology of Southwestern Iowa, 27 
No fossils were found in Nos. 14 and 15, yet they are known 
to have a wide geographical range. No. 13 seems to be some- 
what local in its extent, not having been recognized outside the 
limits of Madison county. It contains numerous fossils, all of 
which seem to be somewhat dwarfed in size, two or three of the 
species not having been found in any other bed. No lamelli- 
branchiates were found in it, nor in any of the beds beneath it, 
yet it is not improbable that they exist in both. Its fossils seem 
to be confined principally to gasteropods and to the spiriferoid 
and terebratuloid brachiopods. In the extreme southwestern 
corner of the county several feet of sandstone were found rest- 
ing upon this bed, which is not seen at all where the section was 
measured. Thus it seems that both this sandstone, and No, 18 
thin out in certain directions, but no indication s of atrue un- 
conformability have been observed. ° No. 11 is a carbonaceous 
band, also of limited extent, not having been recognized outside 
the Limits of the county. 
eds occurring between No. 7 and No. 11, as well as their 
Pra = elsewhere, are much more fossiliferous than other 
portions of the section. A widely extended carbo- argillaceous 
horizon is compas “dings the vertical limits of these few pecs, 
embracing the only bed of coal of the upper series, and also 
number of associated.strata which have resulted from the de 
tion of material that once formed a congenial habitat for oa 
branchiates and gasteropods in addition to the prevailing species 
of brachiopods. e two former classes of mollusks are much 
less numerous in all the other strata, and in the more clearly 
calcareous beds wherever One the lamellibranchiates are com- 
atively rare and appear to be confined to the Anatinide. 
The six or seven upper member, except the carbonaceous beds, 
are principally calcareous, an contain few other than the more 
common upper Coal-measure species, being largely confined to 
the brachiopods. 
The county of Madison contains extensive and very fine ex- 
posures of the rocks of the precedin 6. section, but so ecu 
do the six or seven upper members disappear in all directions 
from its center that they have not been recognized outside of 
its limits, except perhaps to the southeastward a short distance. 
Therefore these beds may be regarded as the most recent of the 
ic rocks now known in the state. The only probable ex- 
ceptions to this, are the gypsum beds of Fort Dodge, the age of 
which is not yet known; and a coarse-grained, friable, ferrugi- 
nous sandstone, to which I have given the rovisional name of 
Nishnabotany sandstone. The latter is found at numerous points" 
in the region of the East Nishnabotany river, sometimes reach- 
ing a thickness of more than thirty feet, and. extends ~ down to 
within thirty miles of the Missouri state line. It has not 
