THE GEOLOGY OF SWITZERLAND. 
4 1 
a species resembling a poplar found in the Cretaceous 
beds of Greenland. In the upper Cretaceous strata 
Dicotyledons are more numerous, and it is interest- 
ing to find that they are mostly species in which the 
pollen is carried from flower to flower by the wind, 
or such as Magnolia, which are fertilised by beetles. 
Bees and Butterflies were still apparently absent or 
rare, and hence also the beautiful flowers specially 
adapted to them. 
Eocene. 
At this period the formation of islands on the 
site of the present Alps appears to have commenced. 
The two principal rocks of the Eocene period are 
the Nummulitic Limestone and the Flysch. They 
represent differences of condition rather than of time. 
Bands of Nummulitic Limestone often occur in the 
Flysch, showing that for a while the sea was favour- 
able for the development of Nummulites. Then the 
conditions changed, and they disappeared. This 
happened again and again. 
Nummulitic Limestone. 
The Nummulitic Limestone is so called because 
it contains numerous Foraminifera, the shells of which 
are in some species so flattened that they resemble 
