STRATIGEAPHY OF THE LIGNITIC FORMATIONS. 11 



well marked on both sides of the river. For a considerable distance both 

 above and below Fort Sarpy, a bed of sandstone forms nearly vertical bluifs 

 on both sides of the river, which I find it difficult to locate. Cretaceous Nos. 

 4 and 5, composed of yellowish-brown indurated clay, with concretions con- 

 taining Baculites ovatus, Rostellarin^ etc , in great abundance, occur, passing 

 into a dark gray coarse-grained sandstone, containing also BncuUtcs ovntus, 

 Avlcula, like A. Nebrascensis, and an Ostrea, new species. This also passes 

 into a sandstone having a most ragged front, from atmospheric agencies and 

 the difference in the consistency of the material composing the bed. It is in 

 the main a coarse-grained, friable, ferruginous yellow sandstone, but contain- 

 ing vast numbers of concretions; some a reddish-yellow arenaceous lime- 

 stone, others sandstone; some nearly compact, with laminse; others divided 

 into thin layers, the harder portions projecting out l)eyond the friable ones. 

 The harder layers lie in the vertical cut, usually from five to thirty feet long. 



"The layers are quite irregular in their horizontal fracture, the whole 

 bed exhibiting indications of having been deposited in moving waters. May 

 it not be the transition bed from the Cretaceous to the Tertiary epoch, the 

 foreshadowing of the Tertiary period?" 



In reviewing the whole of the Reports of Dr. F. V. Hayden and of his 

 assistants, we find similar descriptions of the same great sandstone forming the 

 base of the Lignitic Measures. My own section of the sandstone overlying 

 the Cretaceous No. 4 on the Purgatory River, near Trinidad, New Mexico, is, 

 as will be seen, like a more detailed repetition of Dr. Hayden's description of 

 'the so-called transition sandstone, and also the other sections of the Lignitic 

 productive measures overlying it expose the general distribution of the Lig- 

 nitic beds, as indicated by the numerous sections given in the same Report 

 of Dr. Hayden of the Upper Missouri, or North Lignitic group, thus record- 

 ing the same characters of the measures at both extremes of the North 

 American basin. 



As an example of the distribution of the Upper Lignitic, I copy the 

 section of the Pumpkin Butte, between the Black Hills and the Big Horn 

 Mountains, in the southern part of the North or Missouri Lignitic. It is 

 in descending order:* — 



Feet. 



L Light yellow friable sandstone, with numerous rusty seams 75 



The compact bed of sandstone caps all the hills, and gives 

 them the flat, table-like surface which they present at a distance. 



•Report, 1859-60, p. 73. 



