FV. Hayden on the Cretaceous rocks of the West. 175 
Prof. Heer regards as Miocene, and has more the aspect of up- 
per Miocene or even Pliocene than of the lower Tertiary epoch. 
Nevertheless, the flora is not even Tertiary but really lower Cre- 
taceous. It is found in a fresh-water formation at the bottom of 
the White Chalk of the Missouri Basin. . Hayden 
who first collected these dicotyledonous plants at Blackbird Hill, 
at the Omaha Mission, where a quarry was opened for the pur- 
pose of erecting the mission house. Mr. Heer who saw the de- 
signs of the first collection made at Blackbird Hill by Dr. Hay- 
den, declares that this flora is not Cretaceous, but that on the 
contrary it has a very close analogy with the lower Miocene or 
Oligocene of Europe. But notwithstanding these facts, Mr. 
Marcou saw superimposed upon the rocks with dicotyledonons 
leaves at Pilgrim Hill and on the banks of the Big Sioux, beds 
of chalk containing Inoceramus problematicus, Ostrea congesta, &c., 
and that too without any indications of faults or disturbances 
of strata. “TI yield to the opinion of Mr. Hayden and regard 
these beds as Cretaceous. But I make one reservation; that 
all the Cretaceous beds of Nebraska, and of the upper Missouri 
in general, are very recent and correspond, as also those of New 
Jersey, to the Senonien of d’Orbigny, and perhaps also to his 
uronien.” 
_ following conclusions. 
1. “The rules and laws of paleophytology hitherto adopted and 
followed must be greatly modified, since we find here a flora, 
trasts much greater than those in the distribution of the exist- 
f th 
cal flora of Florida, the Antilles and Panama. After this dis- 
covery I could see no serious objection which would have weight 
in the mixture of Carboniferous plants and Belemnites at Petit- 
Couer in Laventaire, since in Nebraska we have Miocene plants 
underneath 500 or 600 feet of white chalk containing Jnocera- 
mus, Ammonites, and Baculites. 
¢ 
‘The new red sandstone and more especially the lower Lg 
tion or dyas occupies a very important place in the 
Nebraska, as I announced it in 1855 to the Geological Society 
of France, in my geological chart of the United States and in 
the explanatory résumé which accompanied it. ai 
