80 



BRITISH EOCENE FLORA. 



must necessarily also be of that age. When, however, the Mull plants were described 

 by Edward Eorbes in 1851 ^ no more could be said about them than that they might 

 belong to Taxites ?, Eilicites ?, Rhamnites ?, Platanites ?, Alnites ?, and that " the general 

 assemblage of leaves, when judged by the present [1851] state of our knowledge of the 

 vegetation of ancient epochs, is decidedly Tertiary, and most probably of that stage of 

 Tertiary termed Miocene." Heer was subsequently unable to definitely claim more than 

 one, and that perhaps the least satisfactory of all, the Taxites,^ as a Miocene form. We 

 now know that the plants bear at least as strong a resemblance to those of the Cretaceous 

 beds of Dakota as they do to those of any European Miocenes, and much might be said in 

 support of their reference to a late Cretaceous age. But to whatever age it might be 

 possible to assign the Mull Elora, the age of the Antrim Eloras would still be a matter of 

 question, for they have nothing in common, except perhaps a Conifer described now for 

 the first time from Mull, and which could not have been taken into account in former com- 

 parisons of the Floras, They both, however, bear no small resemblance to certain of the 

 Tertiary Eloras of Greenland, whose age I have already demonstrated to be no less open 

 to question.^ Not only has our knowledge of Cretaceous and Cretaceo-Eocene Eloras 

 enormously expanded since their ages were first defined, but we are also gradually 

 becoming aware that the Eocene Eloras were far more changing and varied than had 

 been supposed. We no longer believe that all Eloras comprising modern and temperate- 

 looking genera, such as the Plane, Hazel, Beech, Alder, Poplar, Willow, Elm, Liquid- 

 ambar. Sassafras, Pine, Redwood, and Swamp Cypress must be Miocene, nor that Eloras 

 containing Palms, Proteacege, Eigs, Aralias, Podocarps, and Araucarias, are the only ones 

 distinctive of the Eocenes. 



The time has not yet arrived for entering more deeply into a question which can only 

 be fully discussed when all the plants have been determined ; and it would be useless to 

 attempt now either to point out the actual evidence connecting the plants of the Basalts 

 with the Eocene period, or to dwell upon the absolute insufficiency or rather total 

 absence of evidence connecting them with the Miocene. I will now terminate this 

 digression, rendered necessary at this stage of the work by the progress of our researches 

 and the new series of plants that have in consequence to be incorporated, by a brief 

 description of the actual localities whence they are being obtained. They are so far 

 entirely confined in Ireland to the middle zone of the Basalts. The amygdaloids of which 

 this is largely composed are closely similar to those of the Faroes and Iceland, and are 

 probably of the same age. The plants are already known to occur in white clay, in lignite, 

 in clay-iron-ore, nodular iron, and as silicified wood, at several places ; and it is generally 

 conceded that the three former varieties of matrix are on or about the same horizon, 

 estimated at some 600 feet from the base and 400 feet from the top of the formation. 



Irish bauxite, or hydrate of alumina, is a nearly white aluminous earth which 



1 ' Quart. Journ. Geo]. Soc.,' vol. vii, p. 103. 



^ Sequoia Langsdorjiii, according to Heer. ^ See before, p. 3. 



