94 Beign of Angiosperms. 



identity of a great number of species with those of CEningen, 

 indicates well the synchronism of these two local formations. 

 Such other points in Styria appear likewise to be of the same 

 epoch, as well as many localities in Hungary so rich in silici- 

 fied wood. In Bohemia, the tripoli slates of Bilin and Co- 

 TOothau, which contain a pretty considerable number of plants 

 described by M. de Sternberg, are no doubt referrible to this 

 epoch, according to the nature of these plants. Lastly, the 

 Tertiary hills, called the sub-appennine hills of Plaisantin, 

 of Tuscany, and a part of Piedmont, as well as the gypseous 

 formation of Stradella, near Pavia, so rich in impressions of 

 leaves, form part of this epoch ; but, with the exception of 

 this latter point, these formations contain, in general, few 

 vegetables. 



" In France, the Pliocene epoch probably comprehends a 

 part of the fresh- water deposits of Auvergne and Ardeche. 

 Thus, the slates of Menat and those of Rochesauve appear 

 to me to furnish a Flora very similar to those of CEningen 

 and Parschlug. With regard to the marls of Gergovia and 

 Merdogne, near Clermont, I think they ought rather to be 

 classed in the Miocene epoch ; but this question can be 

 settled only by a more attentive determination of the species. 

 The Flora, which recapitulates all that has been described or 

 named in these formations, is, however, essentially founded, 



zone, the climate of Home, for instance, and not even that of the northern shores 

 of Africa. We are led to this conclusion by the following argument ; — The 

 same isothermal line which passes at present through (Eningen, at the 47th de- 

 gree of northern latitude, passes also through Boston, lat. 42°. Supposing now 

 (as the geological structure of the two continents and the form of their respec- 

 tive outlines at that period seem to indicate), that the undulations of the isother- 

 mal lines which we notice in our days existed already during the Tertiary pe- 

 riod, or, in other words, that the differences of temperature which exist between 

 the western shores of Europe and the eastern shores of North America, were 

 the same at that time as now, we shall obtain the mean annual temperature of 

 that age by adding simply the difference of mean annual temperature which 

 exists between Charleston and Boston (12° Fah.) to that of CEningen, which is 

 48° Fah., as modern O^ningen agrees almost precisely with Boston, making it 

 60° Fah. ; far from looking to the northern shores of Africa for an analogy, 

 which the different character of the respective vegetations would render still less 

 striking. The mean annual temperature of (Eningen, during the Tertiary pe- 

 riod, would not therefore differ more from its present mean than that of Charles- 

 ton differs from that of Boston."— ^^as»«>, on Lake Superior, p. 160. 



