THE FLORA OF THE DAKOTA GROUP. 



By Leo Lesquereux. 



INTRODUCTION. 



The details concerning' the first discovery of leaves of dicotyledonous 

 plants in the strata of the Dakota group, the subsequent researches made 

 l)y Messrs. Meek and Hayden, by Dr. J. S. Newberry, and later by Prof. 

 Jules Marcou, Prof J. Capellini, and Oswald Heer, as well as the e\'ideuce 

 furnished as to the age of the formation by the distribution of animal re- 

 mains in the strata superposed upon it, have all been presented with refer- 

 ence to the data in mv monograph of The Cretaceous Flora (pp. 1-10), which 

 forms vol. (> of the Reports of the U . S. Geological Survey of the Territo- 

 ries under F. V. Hayden.' In the same volume there is also recorded what 

 was then known of the geographical and stratigraphical distribution of the 

 Dakota Group, its superposition upon the Permian, its thickness, the 

 width of its area as recognized in Kansas, Nebraska, and Minnesota, 

 its probable continuity westward under more recent or Tertiary formations, 

 and the manner of deposition of the vegetable remains. 



Later in the Cretaceous and Teiliary Floras, which forms vol. 8 of the 

 Hayden Monographs,^ record is made of the discovery of a number of spec- 

 imens of fossil plants, identical witli or close!}- allied to those of the Dakota 

 Group of Kansas, in Cretaceous strata exposed by upheaval at the base of 

 the Rockv l\Iouiitains of Colorado, a discovery proving the westward con- 

 tinuity of the formation. 



I have nothing to add now to what has been published on these different 

 subjects. A geological survey of the State of Kansas similar to that of 



'Qjioted in this volume as Cret. Fl. ; ibid., Vol. 7, as Tert. Fl. 

 " Quoted in this volume as Cret. and Tert. Fl. 



