ON THE FOSSIL PLANTS OF THE CRETACEOUS DAKOTA GROUP OF THE 



UNITED STATES. 



§ 1. — The discovery of the fossil plants. 



From the beginning of his explorations for the Geological Survey of the 

 Western Territories, Dr. F. V. Hayden had remarked a formation of reddish 

 and yellow sandstone, with variously colored clays, seams of impure lignite, 

 and remains of fossil plants, the whole group holding a position at the base 

 of the Cretaceous series of the Northwest. Already in 1853 he had obtained 

 a number of specimens of leaves of exogenous and dicotyledonous plants, 

 referable, according to his statements of that time, if not to species, at least to 

 genera still represented in our Jlora, or, as he said, 1 closely resembling those of 

 some of the higher types among our existing dicotyledonous forest-trees. In 

 1856 and 1857 the same geologist, then assisted by Professor Meek, found 

 new specimens of these fossil plants in Nebraska; and later in their explora- 

 tions of Kansas, undertaken in common for the purpose of studying the same 

 formation which some geologist had referred to the Trias, 2 they still discov- 

 ered in that State a number of leaves of the same kind. They moreover as- 

 certained that the Kansas formations are in exact correlation, in all their geo- 

 logical characters, with No. 1 of their Nebraska section, now bearing the name 

 of the Dakota Group. From a number of specimens these dicotyledonous 

 leaves of Kansas were recognized as identical with some which had been 

 formerly seen in abundance in strata of this Dakota group at the mouth of 

 the Big Sioux River and at the Blackbird Hills, on the Missouri River, in 

 Nebraska. Among these leaves especially were specimens of a trilobate leaf, 

 mentioned by Mr. Hawes, as found in the measures which he referred to the 

 Trias of Kansas, and which had been exhibited at the Baltimore meeting of 

 the Association for the Advancement of Science. In the discussion on the 

 age of the formation where these fossil plants had been recognized, the dis- 

 coverers, Messrs. Meek and Hayden, remark, in the same paper, that these 



1 American Journal of Science and Arts, vol. xxvii, No. 79, 1859, p. 32. 



a Trias of Kansas, by F. Hawn, Trans. Saint Louis Academy of Science, vol. I, \>. 171. 



