58 
rOPULAll SCIENCE REVIEW. 
shores bordering the same, upon which grew a vegetation vary- 
ing in character, and sometimes localized, according to climatal 
conditions ; in some places sufficiently luxuriant to become the 
source of future beds of coal ; in other places, to be carried by 
rivers or otner means and imbedded with the marine remains 
of the adjacent sea. This vegetation was not, however, of 
uniform character throughout the Cretaceous period, but be- 
came modified and varied in the various stages, and with a 
marked difference in the lower and upper periods. In the 
lower, with the incoming of a new marine fauna, the plant* life 
resembled that of the previous Jurassic age ; whilst in the 
upper, with a comparative similar aspectal fauna, the co- 
temporary vegetation was different from that of the lower 
Cretaceous period, and presented a land facies resembling that 
characteristic of the subsequent Tertiary period, in which the 
forms of the cotemporary marine life were entirely changed. 
In recapitulating the evidence derived from our present 
knowledge of the distribution and character of the Cretaceous 
flora, it appears — 1. That in the different localities from which 
the plants have been described, while the floras have some points 
in common, they are more or less localised in character, pro- 
bably in consequence of different physical and climatal con- 
ditions. 2. That the Upper Cretaceous flora differs considerably 
from the Lower, inasmuch as the latter, by the predominance 
of the gymnosperms, is related to and continuous with the 
previous Wealden and Jurassic flora; while the former, contain- 
i ig a few of the older forms, is marked by the abundance of the 
dicotyledons, thus foreshadowing the subsequent Tertiary flora. 
3. That while in some areas the Cretaceous flora yields generic 
forms, which are now represented and living in the same area — 
as for example in New Zealand, Europe, and America — in other 
places, as in Greenland, there are no such living representatives ; 
and again, some genera, as Sequoia , which were widely dis- 
tributed during the Cretaceous period, are now restricted to a 
single locality. 4. That the appearance of a phsenogamous 
flora in the upper Cretaceous rocks affords a parallel to the 
occurrence in the same formation of the teleostian fishes, both 
of which classes not onl} T increase in the subsequent Tertiary 
period, but are the dominant forms at the present day, as shown 
in the accompanying PI. CXXX. 
These occurrences may indicate either distinct creations, 
adapted to the then existing inorganic conditions, or, when our 
knowledge of the earlier forms is more extended, it may be 
shown to have resulted by modification during long periods 
of time of previous generalised or ancestral types, of which 
there is some evidence in the underlying Jurassic and still older 
formations. 
