292 



MB. J. S. GAEDXEB ON THE LEAE-BEDS 



in Europe with the stage known to continental writers as Paleocene. 

 further, if we accept the stratigraphical evidence linking it to the 

 floras of Antrim, we are able to fix the age of the next overlying 

 flora as not later than that of Gelinden, a flora of ' Heersien ' age, 

 and probably contemporary with our Thanet Beds* ; and to check 

 this by a third and much newer flora, that of Lough is"eagh, in which 

 for the first time the most characteristic plants of the Middle Eocene 

 make their appearance. This evidence, complete as it is, is backed 

 by a large amount of negative evidence, and must carry conviction, 

 unless it is denied that plants in those days followed the ordinary 

 laws of nature and appeared in any definite sequence. 



Thirty-five years ago, when the Ardtun flora was brought under 

 the notice of the Society, scarcely anything was known about fossil 

 plants. The existence of Dicotyledons of Cretaceous age was not 

 even suspected, and except the abnormal flora of Sheppey not a 

 single assemblage of plants of acknowledged Eocene age had been 

 adequately illustrated, while the monographs on Tertiary plants in 

 all did not reach ten in number. The science was in its infancy 

 when Edward Forbes hazarded the opinion that the plants would 

 prove to be of Miocene age ; and those who have been accustomed 

 to regard the age of the Ardtun flora as no less well established than 

 that of Alum Bay will be surprised to realize the slender basis on 

 which the determination has rested. 



The first notice of the occurrence of fossil plants in these Traps 

 was published by the Duke of Argyll in January 1851 f. Though 

 well aware that they were of Tertiary age, he refrained from making 

 any more definite statement regarding them ; but Prof. E. Eorbes, to 

 whom the task of describing the plants themselves fell, thought 

 " that the general assemblage of leaves, when judged by the present 

 state of our knowledge of the vegetation of ancient epochs, is 

 decidedly Tertiary, and most probably of that stage of Tertiary 

 named Miocene."' He was unable, however, to identify any of them, 

 either with forms of the British Eocene J or European Miocene, and 

 was forced to regard them as "in all probability distinct from any 

 recorded species One, however, Platanites hebridicus, he believed 

 to have " a close affinity with Platanus hercules\\, from the marly 

 slates of Croatia ;" and another Taxites ? Camjjbellii, " allied to the 

 Taccites Rosthorni of TJnger, from the Miocene lignite of Carinthia." 

 The remaining six species (really only four) presented apparently no 

 sufficiently decided resemblance to any previously known form to be 

 worth alluding to. We thus see that, when describing them, Eorbes 

 was only able to say that the small fragments of Platanites, which 

 were all he had, were something like an Eocene form from Croatia, 



* Geol. Mag., April 1887. 



t Quart. Journ. Geol. Soc. vol. vii. p. 89. 



t L. c. p. 103. 



§ The known British Eocene floras appear to have been the abnormal ones i 

 of Sheppey and Alum Bay, which certainly bear no resemblance to that of 

 Mull. 



j| Unger, ' Chlor. Protog.,' p. 138, t. 46. They belong actually to very distinct 

 types of leaf. The slates were described as Eocene. 



