1884.] Age of the Tertiary Basalts of the AtUcx>Me. 21 



columnar Basalts, agree in one particular ; they are all characterised 

 by the presence of the peculiar triple nerved leaf called MacGllntocn- / (L 

 The flora of Lough JS T eagh differs considerably from the others. Th e 

 plant-beds, instead of being only a few feet thick, exceed 300 feet j n 

 thickness, and as only the upper part of the mass is accessible, thobo 

 collected may be of newer relative age, as their aspect indeed suggests. 

 The most typical of the older Basaltic plants are absent, but some of 

 the minor leaves are common to Ballypalady and also to Mull, and T 

 do not think they can be placed higher in the Tertiary series than 

 Eocene, and they certainly do not appear to me to be Pliocene, as 

 supposed by the Geological Survey of Ireland. The Mull flora, being 

 among the columnar Basalts, is stratigraphically newer than those of 

 Antrim, with the probable exception of the Lough Neagh beds, and 

 MacGlintochia is absent from it. 



We thus see that the three floras of greatest antiquity, though differ- 

 ing widely from each other in other respects, are all characterised by 

 the presence in them in abundance of MacGlintochia, whilst those 

 which we have stratigraphical evidence for believing to be of newer 

 age are destitute of anything resembling it. 



Now MacGlintochia only occurs in one stratum whose age has been 

 fixed wholly independently of plants. This is the Heersien stage of 

 Gelinden, a stage very low down in the Eocene of Belgium, and older 

 than any Eocene represented in England. Our floras from the Wool- 

 wich and the Reading beds are now tolerably well known. They are 

 younger than the Gelinden flora, and contain no MacGlintochia, just . 

 as we have remarked with the younger floras of the Basalts, but the 

 prevailing type in them, a Platanus, does occur at Louoh Neagh. 

 Here we have fossil evidence of precisely the same nature that we have 

 been accustomed to regard as conclusive when dealing with anything 

 but vegetables — MacGlintochia characterises the Heersien stage in the 

 only locality in which a flora of that age is known, and it is not met with 

 elsewhere or at any other horizon in Europe. There is not a particle 

 of other positive evidence as to the age of the Antrim Basaltic floras, 

 except that they are posterior to an horizon in the White Chalk, but 

 the physical grounds for assigning a high antiquity to the Basalts are 

 overwhelming. This is not the place to enter into them, and I have 

 recently stated them at some length. The floras cannot be Miocene, 

 for they have not a single plant in them common to any European 

 Miocene deposit, and if Eocene, they must, in the absence of anything 

 contradictory, be placed in the only Eocene horizon in which pre- 

 cisely the same plants are found. The same with the Lough Neagh 

 beds; stratigraphically they appear to be newer than the rest ; they 

 contain a particular plant that the others do not, and this plant is 

 eminently characteristic of the Reading series of the Eocene and of 

 no other, for it is absent from the older flora of Gelinden, just as it 



