10 

 § 2. — Surface distribution of the dakota group. 



In order to illustrate the geological relation of the species of fossil plants 

 described in this memoir, it is convenient to make some remarks on the distri- 

 bution of the group wherein they have been discovered. In doing this it will 

 be advisable to record facts already published by geologists who have formerly 

 explored this formation — by Dr. Hayden especially, by Professors Meek, 

 Mudge, Conrad, Marcou, Capellini, Hall, &c. These records and quotations 

 are rendered necessary by the scattering of the materials referring to this 

 group in scientific journals which are rarely accessible to paleontologists. 



The eastern limits of the surface area of the Dakota group are marked in 

 the Geological Report of Iowa, by Prof. C. H. White, who recognizes the 

 most easterly deposits of this formation, which he calls the Nishnabotany 

 sandstone, in the southeast part of Guthrie County, and as far south as the 

 southern part of Montgomery County. To the north it passes under the 

 Woodbury sandstone, overlaid by the Inoceramus, or chalky beds. The north- 

 western counties of Iowa have not been yet surveyed in detail, and owing 

 especially to the few exposures of the rocks underlying the drift, and the 

 prairies which cover this region, the exact limits of the group are not here 

 distinctly recognized. The direction, however, is, in Iowa, from near Council 

 Bluffs north and somewhat east to the point where the Des Moines River 

 leaves Minnesota, and hence due north to the mouth of the Big Cotton- 

 wood River, near New Ulm, where the red sandstone is exposed in the 

 bank of the river. From this locality Professor Hall has recognized it 

 one hundred and thirty miles farther north. From Council Bluffs, or from 

 above the mouth of the Platte, in Nebraska, the border of the belt passes in 

 the same direction, south a little westward, across the western part of Cass 

 and Otoe Counties ; thence to the middle of Gage County, near Beatrice ; 

 then through Marshall County, entering Kansas in the eastern corner of Clay. 

 It descends farther south to the mouth of Solomon River, and reaches the 

 Arkansas River west of the line of the Atchison, Topeka and Santa Fu Rail- 

 road, near the mouth of Cow Creek. 



I can find no data marking the borders of the belt, nor even recording 

 its appearance in the Indian Territory, between Kansas and Texas. But 

 subsequent geological investigations cannot fail to recognize it in that country, 

 as its connection cannot be broken in that, as yet unexplored, region alone. 

 The records of the geological surveys of Texas and of Arkansas indicate it 



