126 KANSAS ACADEMY OF SCIENCE. 
formation definitely in the Cretaceous. The following is Doctor Hayden’s state- 
ment: 
‘The discovery at Blackbird hill during the past year of dicotyledonous leaves 
allied to the oaks, willows, and others of our deciduous forest-trees, together 
with their position with regard to other well-known Cretaceous formations, ren- 
ders the evidence quite clear that a large portion of the strata which we had in- 
cluded in No. 1 of our vertical section is of Lower Cretaceousage. . . . Major 
Hawn has found the same or similar leaves in the formation in Kansas. Ae 
We have, therefore, arrived at the conclusion that No. 1, as it is revealed from 
Council Bluffs to the Big Sioux, is Lower Cretaceous, although two or three beds 
of yellow or ash-colored clays exposed at low-water mark near Blackbird hill may 
be Upper Jurassic.’’ ” 
It is interesting to note the extreme slowness with which these distinguished 
scientists reached their conclusions regarding the age of this formation. Their 
opinion once formed, however, they never afterward changed it, and the geolog- 
ical world gradually came to accept their position. It was about this time that 
Meek and Hayden, desiring some paleobotanical evidence on the age of the beds, 
sent to Prof. Oswald Heer, the distinguished phytopaleontologist of Zurich, 
some outline sketches of a few of the plants. Not having heard from him for 
some months, the entire collection of fossil leaves was submitted to Dr. J. S. New- 
berry, who, after studying the forms, referred them to thirteen genera, and un- 
hesitatingly placed them in the Cretaceous. This was in November, 1858.!° 
The same year Prof. G. C. Swallow published a paper entitled ‘‘ Rocks of 
Kansas.’’!4 The sections given were made along the Kansas and Smoky Hill 
rivers, apparently as far west as Ellsworth county. The rocks of the state were 
divided into five groups, viz.: Quaternary, Cretaceous, Triassic, Permian, and 
Carboniferous. The Cretaceous rocks included the limestones and shales which 
are now known as the Fort Benton, and the 420 feet of sandstone and shale be- 
tween these rocks and the Permian were designated as Triassic (?), although, in 
a foot-note, the statement is made that the name is only provisional and did not 
refer to the known age of the rocks. 
The Dakota group, or rather the formation which has since received that name, 
was at this time (1858) considered as Triassic by Swallow and Hawn; as Juras- 
sic by Marcou; and as Cretacous by Meek, Hayden, and Newberry. To add to 
the complication of the problem, Meek and Hayden received, on December 15 of 
this year, a letter from Professor Heer, in which he referred the plants, of which 
sketches had been sent him, to six genera, and inclined to the opinion that they 
were of Tertiary age.” ! 
At the same time Professor Marcou published a paper addressed to ‘‘ Messrs. 
F. B. Meek and F. V. Hayden,”’ in which he quotes the conclusions of Professor 
Heer, and expresses the opinion that No. 1 of the Nebraska section is both 
Miocene and Jurassic.‘° In other words, he thinks that there are included in 
this group strata belonging to these two widely separated geological epochs. In 
their paper read December 21, Meek and Hayden express a high regard for the 
opinions of Professor Heer, but state that it is impossible for the formation to be 
Tertiary. They attribute his mistake to the fact that he saw only imperfect 
sketches of the leaves.!’ Concerning the matter, Doctor Lesquereux afterward 
said: ‘‘From what we know of the character of the Dakota leaves, it is clear 
that, judging from mere sketches, the celebrated professor of Switzerland could 
scarcely have come to a different conclusion.’’ ® 
12. Proc. Phila. Acad. Sci., 9: 189-157. 13. Proc. Phila. Acad. Sci., 1858, p. 257. 
14. St. Louis Acad. Sci., 1: 173-175. 15. Proc. Phila. Acad. Sci., 1858, pp. 265, 266. 
16. J. Marcou, Zurich, 1858, 16 pp. 17. Loc. cit., pp. 257, 258. 
18, Cretaceous Flora, U. 8. Geol. Surv. of Terr., 6: 4. 
