of Geological Periods. 345 



Liquidamhar europoeum, Al. Br. Horw (Switzerland), Sagor (Germany). 

 Cornus orbifera, Heer. Monod. 



Studeri, Heer. Monod. 



Hedera Maclurei, Heer. Greenland. 

 Liriodendron Procaccinii, Ung. Eriz, Iceland. 

 Acer trilobatum, Al. Br. Manosque, Monod. 



Ruminianum, Heer. Manosque, Monod. 



otopteryx, Gopp. Iceland. 



Juglans bilinica, Ung. Manosque, Monod, Iceland. 



acuminata, Al. Br. Greenland. 



Cratagus tenuifolia, Sap. Clay of the Marseilles basin. 

 Cercis Tournoueri, Sap. Brognon. 



The list is still complete ; but some of these genera will no 

 longer appear. Such are Platanus, Fraxinus, and Liquidambar ; 

 and it is to be remarked that these are not the most northern 

 forms. The Platani and Liquidambars prefer the warm tem- 

 perate zone — a circumstance which explains their exclusion from 

 Europe by the effects of the glacial period. Here the first 

 known traces of these genera make their appearance in the 

 Arctic regions, which then possessed species in common with 

 Europe, and which, although warmer than at present, were 

 nevertheless subject to the influence of latitude, since the species 

 with deciduous leaves already predominated there, and several 

 of them only spread at a later period over the middle of Europe, 

 such as Betula prisca and macrophylla, Platanus aceroides and 

 Acer otopteryx — a phenomenon still obscure, but of great in- 

 terest, if we succeed in ascertaining it with precision. 



In approaching the Tongrian or fourth horizon, a decisive 

 period in the question under examination, I find it preferable, 

 from the rather complex affinities of the floras which I refer to 

 it, to divide them into two partial horizons — one, more recent, 

 nearly approaching that which we have just quitted, the other 

 including the Tongrian properly so called. On the former I 

 place Radoboj and Armissan (very rich localities, which present 

 a remarkable correspondence), and we thus obtain the following 

 list :— 



Alnus microdonta, Sap. Armissan. 

 Betula dryadum, Brong. Armissan. 



Ungeri, Andr. Radoboj. 



Ostrya atlantidis, Ung. Radoboj, Armissan. 

 Carpinus grandis, Ung. Radoboj. 

 Quercus magnoUceformis, Sap. Armissan. 



oligodontay Sap. Armissan. 



sinuatiloba. Sap. Armissan. 



Castanea paleeopumilay Andr. Armissan. 

 Fagus atlantica, Ung. Radoboj. 

 Ceitis primigenia. Sap. Armissan. 

 Ulmus Bronnii, Ung. Armissan. 

 priscay Ung. Radoboj. 



