48 General Notes. [ January, 
the most eminent geologists of this side of the Atlantic the gaps which 
distinctly separate the cretaceous from the lower tertiary were admitted 
as corresponding to the end of a great period, and marking its separation 
from the following one, abruptly beginning a new order of things. 
Thanks to the American discoveries due to Dr. Hayden’s perseverance 
we have now before us a formation composed of a union of strata of 
surprising extent, and these strata when they become carefully studied 
will teach us how the transition between the upper cretaceous and the 
most ancient tertiary has proceeded. 
The radical separation, admitted until now, of the secondary times in 
regard to those which follow, is therefore uncertain in such a way that 
if geological researches, instead of beginning in Europe, had been first 
made in America, the classification would have been modified according 
to the facts recently obtained by Dr. Hayden; and we can even assert 
that it would have been founded upon at least different if not opposite 
bases. The natural consequence of the discovery of these new forma- 
tions has been a rich harvest of animal and vegetable fossil remains, 
vertebrate and invertebrate. Here I will only speak about the plants 
which by their profusion and their variety form a complete herbarium, 
by which Mr. Lesquereux, as learned as modest, will be able to patiently 
reconstruct the vegetation of an epoch of which, a few years ago, even 
the existence was still unknown, at least contested. Nothing, indeed, 
was more obscure than the flora of the second half of the cretaceous 
until the Dakota group offered us their share of vegetable fossils. This 
obscurity was, and is still, a great obstacle to the study of those plants 
which show us the most ancient Dicotyledons, and take us back to an 
age when the vegetation of our globe was being completed by the ad- 
dition and the rapid development of the highest and most numerous ` 
class which composes it at our time. Before this epoch, reduced as it 
was to a small number of relatively inferior types, the vegetation could 
evidently furnish to large land animals insufficient food. It is only from 
the appearance of the Dicotyledons just at the epoch when the strata 
of the Dakota group were deposited, that both kingdoms began their 
completion by the rapid and successive development of what they have 
most perfect in land animals and plants, before the arrival of man him- 
self, this last complement of creation. 
Not only have the plants of the Dakota group presented to us types 
of which we could not’ formerly suppose the antiquity, but in the ter- 
tiary system which immediately follows the Dakota group, in the lignitic 
formation, the researches inaugurated by Dr. Hayden have already ex- 
posed to our knowledge the remains of a number of floras of various 
stations and of great richness. This vegetation, distinct from that of the 
Dakota group, is far more recent, but it has also its proper interest. Its 
relation with European contemporaneous floras has to be determined ; 
its most interesting study will demand a great deal of patience and 
