278 Annals of the Carnegie Museum. 



In 1878 Hayden published 500 copies of the plates under the title of 

 " Illustrations of Cretaceous and Tertiary Plants." 



In 1874 Lesquereux published his " Cretaceous Flora." Other pub- 

 lications followed by Lesquereux, and in 1885 he began his work on 

 the " Flora of the Dakota Group." This was submitted to the pub- 

 lishers in 1888, but before it was published Lesquereux died (1889). 



The book was published three years later (1892) by Dr. Knowlton. 

 Many other writers have contributed short articles on the " Dakota 

 Group," but very few species, not described in the " Flora of the 

 Dakota Group," have been added to the large number of species fig- 

 ured and described in this admirable work. 



Deposition and Present Distribution of the Dakota Formation. 



The " Dakota Formation " is found in the middle western part of 

 North America. It is rather extensive in the Great Plains, but is 

 mostly buried by later formations (Chamberlain and Salisbury's Geol- 

 ogy, Vol. Ill, 1906, p. 144). The type locality is Sioux City and 

 Blackbird Hill, where, with other portions of Kansas and Nebraska, 

 it is found in comparatively large areas. It extends west of the 

 Rocky Mountains, but is interrupted by high elevations along these 

 mountains. It has been found distributed in portions of Kansas, Ne- 

 braska, Minnesota, South Dakota, Wyoming, Colorado, Oklahoma, 

 New Mexico, and other States. North of the United States it appar- 

 ently has been found in the Frazer River Valley and in the eastern 

 part of Crow's Nest Pass. (See Dawson, Bulletin Geological Society 

 of America, XII, pp. 77-78.) 



Knowlton, in discussing the succession and range of the Mesozoic 

 and Tertiary floras, says that in the interior of North America, in 

 approximately the same position as the Magothy of the Atlantic bor- 

 der, " is the Dakota, which has afforded a splendid flora of over five 

 hundred species, and occurs in Kansas, Nebraska, Wyoming, Minne- 

 sota, along the international boundary, and some of the same forms 

 as far as central Alaska and south to Argentina." ("Outlines of 

 Geologic History," Willis and Salisbury, 1910, p. 206.) 



The formation is chiefly non-marine, consisting largely of sand- 

 stone, with conglomerate, clay, and a little lignite. The deposition 

 took place evidently in the shallow water of lakes, rivers, and marshes. 



