1886. | | Geology and Paleontology. 269 
differed from that of Europe. But when we reach Aix-la-Chap- 
elle, we find the chalk and greensand resting upon beds contain- 
gams. Nor does the 1200 or 1400 feet of vertical chalk remaining 
in our area at all represent the completed formation; for, as the 
prolonged subsidence finally ceased and gave place to an equall 
slow elevation, all the lessening zones of depth would travel back 
with the receding ocean, and leave a series of zones inversely arrang- 
ed tothat preservedto us. The planing action of the sea has re- 
moved all this newer series, just as it has planed away a further. 
mass of the width of the English channel, and is slowly but in- 
- exorably cutting down to its own level all the zones that form its 
shore lines. The Eocene seas from beginning to end of the period 
were ceaselessly engaged in this work, and their enormous deposits 
of flint shingle mark how much of the chalk had fallen a prey to 
them. Nor has the chalk enjoyed any respite from the work of 
destruction down to the present day, so that what now remains 
isa mere fragment of what once existed. It was during the in- 
terval that elapsed between the formation of the newest chalk now 
left in England and the oldest Eocene that dicotyledons were 
introduced, and our existing flora practically came into existence. - 
All the Upper Cretaceous floras of Europe also flourished during 
this interval, but we cannot say, with our imperfect record, exactly 
the order in which they came in, and must be content to regard 
them in a general way as far newer than they appear to be strati- 
graphically. The entire American Cretaceous series should, per- 
haps, also be placed somewhere in this interval, though those well 
qualified to judge regard its commencement as dating from an 
older period. Without this digression we could not have formed 
an adequate idea of the meaning of the “ Cretaceous period” and 
So realized that the so-called Cenomanian and Turanian floras 
of Europe may belong to a completely different epoch to that 
represented by the same horizons in Kent and Sussex, — F., S. 
Gardner. r j 
1 Š j i 
bers viou American Ka of Natural a Hy L | No. 6, r 7 ; 
