46 
THE CEETACEOUS FLORA. 
By J. MORRIS, F.G.S., 
PPtOFESSOE, OF GEOLOGY IX EXIYEPvSIXY COLLEGE. 
[PLATE CXXX.] 
T HE conditions nnder which the various sedimentary strata 
were accumulated, and the inferences deducible as to the 
physical geography and climatal characters of the different 
periods, may be understood not only from the study of the sedi- 
ments themselves, but more especially from the nature and 
relations of the remains of the fossil animals and plants imbedded 
in them. The greater portion of the vast thickness of the 
stratified formations (estimated at from twelve to sixteen miles, 
and even more, in thickness) are chiefly due to marine agency, 
with some intercalated beds of estuarine and fluviatile origin, 
while others are indicative of old terrestrial surfaces which must 
have been to some extent more or less contemporaneous with 
the aqueous deposits then in progress. The evidence of this old 
land is inferred from the nature of the vegetation and the occur- 
rence of the remains of air-breathing animals associated with it. 
The general geological belief appears to be — from the nature 
of the evidence preserved to us in the successively formed 
fossiliferous rocks — that from the earliest period to the present 
there has been a gradual increase of the land-surface of the 
globe. The remains of the animals and plants all point in this 
direction. 
In the Upper Palaeozoic period there was a luxuriant land vege- 
tation, some insects, and air-breathing reptiles ; in the Mesozoic 
period many land plants, insects, air-breathing reptiles and 
warm-blooded mammals, chiefly marsupials, and in the succeed- 
ing Tertiary or Coenozoic period a considerable increase in 
numbers of the orders and families of animals and plants, both 
of which have attained their maximum at the present time. 
With regard to the development of the vegetable kingdom 
in time, Mons. Adolphe Brongniart many years since divided it 
into three great periods corresponding to those above mentioned : 
