INTRODUCTION. 5 



Newer Oligocene {Oligochie recent) or passage-beds to Aquitanian. — Armissan near 



Narbonne, and Brognon, Cote-d'Or. 

 Lower Aquitanian. — Lignites of Manosque (Basses Alpes). 

 Upper Aquitanian. — Clays of the Marseilles Basin and Schists of Gergovie. 

 Lower Miocene. — Menat in the Auvergne. 

 Upper Miocene. — Mont Charray. 

 Newer Miocene {Miocene recent). — Flora of Theziers. 

 Lower Pliocene. — Cinerite du Cantal, basaltic tufas of Auvergne, and tufas of 



Meximieux. 

 Middle Pliocene. — Tufs de la Valentine near Roquevaire (Bouches du Rhone), and 



Marnes de Ceyssac^ Haute Loire. 

 Upper Pliocene. — Marnes de Burfort (Gard). 



Twenty-three localities from which floras have been obtained are enumerated in this 

 list. Those between the Gypsum of Aix and the Lower Miocene of the Auvergne form 

 a practically homogeneous series in one locality, and are, therefore, of great value in 

 tracing the gradual decrease in temperature, and the consequent departure or modification 

 of the Tertiary plants of Europe. 



Our British series is thus supplemented in Prance by both older and newer floras ; 

 and is repeated from the Middle Eocene upwards, but in a still more complete form, and 

 seven degrees further to the South. 



In America the conditions seem to be even more favorable, since a vast series of 

 floras, ranging in age from Cretaceous to Pliocene, is known to exist in the Western 

 Territories of the United States. If these can be connected, by the work of Principal 

 Dawson, with those of the Arctic Circle, and if these floras and our own are ever studied 

 with the same care that the Marquis de Saporta has bestowed on those of France, the 

 results must be of most extreme value. A scale could then in time be constructed by 

 which the ages of fossil floras of even remote countries might be determined, but 

 which must otherwise remain doubtful. Such determinations are at present liable 

 to error, as there are no recognised and fixed types from any latitude which are 

 universally acknowledged to be characteristic of either the Cretaceous, Eocene, or 

 Miocene systems. 



In the first place, in determining the relative ages of fossil floras, the probability that 

 temperature differed in somewhat the same degree as at present, in different latitudes and 

 longitudes, seems seldom sufficiently considered, and an almost universally equable tem- 

 perature in the Eocene and Miocene times has been assumed, without evidence that 

 such was the case. The similarity between such widely separated fossil floras as those 

 of Iceland and Italy renders it very improbable that they could be of the same age, 

 especially if the causes which led to the increased warmth during the Eocene in 

 high latitudes were purely terrestrial. Again, the probable nature of the station 



