Cretaceous Rocks of Iowa. — Calvin. 301 
1. Irregular beds of sandstone, varying in color and texture, and 
interstratified with thin beds of shale 18 ' 
3. Grayish and mottled shales with thin ferruginous bands and 
arenaceous layers 13 ' 
3. Massive sandstone, mostly soft ; but in places containing 
large concretionary masses, several feet in diameter, in ap- 
pearance and hardness resembling quartzite 10 ^ 
4. Shales with usually two, but sometimes more, well marked 
thin bands of ferruginous concretionary sandstone. ("But- 
tons" of the clay workers.) 16 ^ 
.5. Band of impure lignite 4 to (i inches 
6. Blue, yellow and red mottled clays (terra cotta clays) with 
selenite crystals and some streaks of sand 30 ^ 
7. Argillo-calcareous or arenaceo-calcareous beds with much 
selenite (varying with locality) 20 ^ 
8. Shales more or less unctions to the feel, somewhat variable in 
color and texture, containing remains of saurians and tele- 
ost fishes, the upper beds sometimes bearing impressions of 
Inoceramus problematicus 40 ^ 
9. Calcareous beds consisting of chalk and soft, thin bedded lime- 
stone, containing shells of riiocerarrms problematicus, Os- 
trea congesta, and teeth of Otodus, Ptychodus and other 
selachians 30 ^ 
Beds that are quite constant and easily recognizable in the re- 
gion about the mouth of the Big Sioux river are Nos. 3,4,5,8 and 
9. These, either singly or collectively, become the guides whereby 
the beds of the several exposures may be correlated. The deposits 
were traced up the Big Sioux valley for a distance of forty miles ; 
they were followed up the Missouri river as far as Yankton. 
In addition to the deposits exposed on the Big Sioux, Dr. C. A. 
White, under the name of the Nishnabotna sandstone, refers to the 
Cretaceous age a series of sandstones developed to a thickness of 
100 feet along the river valleys in Montgomery, Cass, Guthrie and 
Greene counties. Referring to the work done by Meek and Hay- 
den on the Cretaceous deposits exposed along the Missouri river 
and noting the names employed by these authors to designate the 
various subdivisions of their "Earlier Cretaceous," Dr. White 
saj's: " The Cretaceous strata of Iowa have so slight a develop- 
ment in comparison with those farther up the Missouri river, that 
it is difficult to determine their stratigraphical equivalents with- 
out actual comparison, which it has thus far been impossible to 
make. There is no doubt, however, that all the Iowa Cretaceous 
strata belong to the ' Earlier Cretaceous ' of Meek and Hayden, 
nor any doubt that the lowest portions of ours is equivalent to a 
part of their Dakota group." (White's Geology of Iowa,\o\. i, p. 
288,1870). Without attempting, therefore, to synchronize theCh-eta- 
ceous of Iowa with the Cretaceous formations studied by Meek 
