294 



ME. J. S. GAEDNEE ON THE LEAF-BEDS 



nites is probably the Bercliemia ; the Fern is of a type unknown on 

 the continent. He thus differs in detail from De la Harpe, and is 

 indisposed to admit that the flora contains either Alnus, Acer, or 

 Bhamnus, the presence of which had convinced the latter as to the 

 Miocene age of the flora. His four rather hesitating identifications 

 sufficed, however, to induce him to speak even more positively than 

 De la Harpe, who had at least seen the specimens, as to the age of 

 the beds ; but he reduces the value of his evidence by only admitting 

 two, the Sequoia and the Platanus, into the exhaustive tables which 

 conclude his great work on the Tertiary Flora of Switzerland. I 

 cannot trace that these identifications were in any way increased or 

 modified after Heer's visit to England : but in 1862 he changed the 

 name of Corylus grossedentata, of the Aquitanian of France and 

 Switzerland, to Corylus MacQuarrii, Forbes, sp.* 



This completes the evidence upon Which the Miocene age of the 

 Basalts was defined ; for in the 6th edition, 1865f , and all subse- 

 quent editions of Lyell's 4 Elements,' and ' Student's Elements of 

 Geology,' we find the following : — " and his [Forbes's] opinion has 

 been confirmed by Prof. Heer, who found that the Conifer most 

 prevalent was the Sequoia Langsdorjii, also Corylus grosse-dentata, 

 a Lower Miocene species of Switzerland and of Menat, in Auvergne." 



Thus the age of the beds has been based on the lithographs of 

 four species, wanting in detail, and represented by mere fragments 

 of leaves, which even De la Harpe, who was not easily discouraged, 

 regarded as " peu determinable" the specimens being, in fact, in 

 black shale, and by no means easy to make out. 



A letter from Heer to Ch. Gaudin, dated 1856, published in the 

 Bull, de la Soc. Yaudoise, shows that the only floras recognized by 

 him as Eocene at that period J were known to him from the descrip- 

 tions, without illustrations, published by Gaudin and by Brongniart, 

 from Bowerbank's work on the English Eocene plants, and the flora 

 of Monte Bolca. All others, though described as Eocene in published 

 works, he regarded as Miocene §. It is easy to see how, with the 

 ordinary types of Eocene floras (and some of the isolated Swiss floras 

 may be Eocene), grafted on to the Miocene floras, there was always 

 at hand a scale by which every flora, except such abnormal ones as 

 those of Sheppey and Alum Bay, would be determined to be Miocene, 

 and be of use in turn in incorporating floras of even more widely 

 different ages. On the plant-evidence, Heer would have pronounced 

 the Beading and the Bournemouth floras to be Miocene had they 

 been known then ; for they have a very large number of species in 

 common with European floras he had already so placed. He did, in 

 fact, pronounce an American Cretaceous flora sent him to be Miocene, 

 so that it is obvious he was not in a position to offer any sound 



* Naturf. Gesellsch. Zurich, 1862, p. 178. 

 t Lyell, ' Elements,' ed. 6, p. 239. 



J " Oil est done la flore eocene ?— Je n'en connais pas ailleurs qu'au Monte 

 Bolca, en Angleterre, et dans le bassin de Paris." 



§ " Cet examen m'a parfaitement continue 1' opinion que Having, Sagor, 

 Sotzka, Radoboj, de meme que le Monte Promina sont miocenes et non point 

 eocenes" (Bull. Soc. Vaudoise, 1856.) 



