520 VEGETABLES OF THREE EPOCHS. 
great numbers of fossil Crustaceans, and also the 
remains of many fishes, and of Crocodiles, and 
aquatic Tortoises. 
As the drifted seeds that occur in Sheppey 
seem to have been collected by the action of 
marine currents, the history of European vegeta- 
tion during the Tertiary period, must be sought 
for in those other remains of plants, whose state 
and circumstances show that they have grown 
at no great distance from the spot in which they 
are now found.* 
Conclusion. 
The following is a summary of what is yet 
known, respecting the varying conditions of the 
Flora of the three great periods of Geological 
history we have been considering. 
The most characteristic distinctions between 
the vegetable remains of these periods are as 
follows. In the first period, the predominance 
of vascular Cryptogam ic, and comparative rarity 
of Dicotyledonous plants. In the second, the ap- 
proximation to equality of vascular Cryptogamic, 
and Dicotyledonous plants. t In the third, the 
predominance of Dicotyledonous, and rarity of 
* The beautiful Amber, which is found on the eastern shores 
of England, and on the Coasts of Prussia and Sicily, and which is 
supposed to be fossil resin, is derived from beds of Lignite in 
Tertiary strata. Fragments of fossil gum were found near Lon- 
don in digging the tunnel through the London clay at Highgate. 
t The dicotyledonous plants of the Transition and Secondary 
