GEOLOGY AND PALEONTOLOGY. 1:23 
ber of new species of plants collected during the field seasons of 1898 and 1899, by 
Dr. Lester F. Ward and the writer. Before the studies of the leaves were com- 
pleted, however, Doctor Ward suggested that a monograph of the Dakota group 
be prepared with such geological discussions as recent investigations demanded, 
paying particular attention to the new species of plants. After consultation 
with Dr. Erwin H. Barbour, under whose direction the work was being done, it 
was decided that while such a work was feasible it was manifestly impossible to 
complete the entire subject in the limited time allowed. This necessitated a 
change in the plan of the work. The present paper, therefore, should be con- 
sidered preliminary in character. The writer is not unmindful that the discus- 
sions are in places more in the character of a popular report than of a technical 
presentation of scientific data. This fact, however, may not necessarily be re- 
garded as an unmixed evil. The work on the monograph along the lines sug- 
gested by Doctor Ward is in progress. The writer hopes within a reasonable 
time to present to the scientific world this contribution to the knowledge of one 
of our most interesting of geological groups. 
In the work of the investigation of the various problems ccnnected with the 
Dakota, I have had the kindly assistance and suggestion of Dr. Lester F. Ward 
and Dr. T. W. Stanton, of the United States Geological Survey. In the prepa- 
ration of this article, I have been especially fortunate in the aid and criticism of 
Dr. Erwin H. Barbour and Mr. C. A. Fisher, of the University of Nebraska. To 
each of these gentlemen are due my heartfelt thanks. 
HISTORICAL SKETCH, 
No attempt has been made to prepare an exhaustive treatment on the history 
of the Dakota group. The literature is not only considerable but it is also 
widely scattered. Of the hundreds of articles and references dealing with 
this group, but a few of the most important will be cited. The subject naturally 
divides itself into four general heads, which have been somewhat loosely followed 
in the discussion. The first period, or that of early discovery, begins in 1804, 
and ends in 1856. The second extends from 1856, when Meek and Hayden began 
their famous controversy concerning the age of the beds, to 1864, the date of the 
publication of Mr. Marcou’s paper in which he admits the Cretaceous age of the 
formation. The third period, during which Dr. Leo Lesquereux figured so promi- 
nently, began in 1866, and closed with the publication of ‘‘ The Flora of the Dakota 
Group” in 1892, after the death of Doctor Lesquereux. The last period deals 
with the question of invertebrates and recent investigations. 
For a more detailed account of the subject the reader is referred to the articles 
cited in the bibliography at the close of this paper. This bibliography, however, 
makes no pretentions to completeness. 
EARLY DISCOVERIES. 
It is to the records of the exploring expedition of Lewis and Clarke, which in 
1804 ascended the Missouri river, that we must go for the first mention of the 
sandstone now known as the Dakota group. Previous to this time French and 
English traders and trappers had gone up the river, and had even built tem- 
porary trading stations along its banks; but these men, interested in pecuniary 
gain alone, left no record of the natural scenery of the country. The first account 
of the Lewis and Clarke expedition was published by Patrick Gass, a member 
of the party, in 1807. Under the date of August 10, 1804, Sergeant Gass says: 
** We stopped to examine some high yellow banks on the south side and camped 
on the north side.’’! 
1. Jour. of Voyages, etc., of Lewis and Clarke, by Patrick Gass, pp. 27-28, 1807. 
