106 MRS. E. M. BEID ON TWO [vol. lxxvi.,. 



At the end of his letter he added 



' The dried seeds in the bottle were certainly, I recollect, derived from the 

 more bluish clay with ostracods.' 



Dr. Trechmann's letter confirmed, therefore, the opinion that the 

 recognized difference of floras corresponded to difference of strata. 



The 11 British species found in the small sample are all temperate 

 species. There is nothing to indicate a climate differing from that 

 of the present day, unless it be that some are rather undersized. 



From the foregoing statements it will he seen that an exami- 

 nation of fossil seeds made it possible to discriminate between 

 strata which were intimately mixed, not only in situ, but in the 

 way in which their fossil contents reached me. 



The further point that I wish to make is this, that it is now 

 possible to determine the age of Pliocene strata by 

 examination of the contained seeds. 



It happened that at the beginning of 1919, while I was still 

 engaged upon the Castle-Eden flora, I received material from Pont- 

 de-Gail, in the department of Cantal. It was sent by M. Of. F. 

 Dollfus & M. P. Marty, who together had made an examination of 

 the deposit. The evidence of the mollusca showed that the deposit 

 lay at the base of the Pliocene. 1 



This material, for the first time in the study of Pliocene seeds, 

 supplied the knowledge of a seed-deposit low down in the Pliocene, 

 the age of which was known. Hitherto the only seed-deposits of 

 known age were the Cromerian and the Teglian. Both were Upper 

 Pliocene, the one at the top, the other near the base. The age of 

 the large Reuverian flora was not known. All we knew was that it 

 contained many more exotics and extinct species than the Teglian, 

 and must, therefore, be older. We suggested that it should be 

 placed at the top of the Middle Pliocene ; a suggestion I now know 

 to be wrong. It is Lower Pliocene. 



While examining the Pont-de-Gfail collection 2 I was constantly 

 impressed by its general resemblance to the Reuverian. There was. 

 the same large number of exotic and extinct species, the same 

 abundance of species belonging to the Chinese and North American 

 association, and, in this comparatively-small flora of 18 species, 

 three were Reuverian. So striking was the resemblance that I was 

 led to attempt a comparison. The difficulty lay in deciding what 

 data to take, when determinations were necessarily of varying 

 degrees of reliability and value. I decided to consider only those 

 species the determination of which I felt confident was accurate so 

 far as it went, and which had been carried far enough to show 

 something definite as to the present distribution of themselves or 

 their nearest allies. I extended the comparison also to the Teglian, 

 so as to learn, in the event of the Reuverian flora lying between 

 the two, where its probable position would be. 



1 ' Dt'couverte d'un Gisement Fossilifere dans le Cantal ' C. P. Acad.. 

 Sci. Paris, vol. clxvii (1918) pp. 534-35. 



2 E. M. Reid, ' Eecherches sur quelques Graines Pliocenes de Pont-de-Gail 

 (Cantal) ' C. P. Soc. Geol. France. No. 6, Seance du 15 Mars. 1920 



