22 Agefifrj? fj ie Tertiary Basalts of the Atlantic. [Dec. 18, 



is in An^ r | mj an( j f rom a n the newer floras of the Eocene. I have 

 chos-, en the commonest and most striking types to base my argument 

 n P°jn, for the sake of brevity, but I could support them by reference 

 to ^he other plants which, so far as I have examined them, entirely 

 support them. 



Were the belief in the Miocene ages of these beds not so deeply 

 rooted, it would be unnecessary to prove what is self-evident. Where 

 the ages of Tertiary rocks have been decided upon plant evidence 

 alone, we should, I think, accept them for the present with great 

 reserve. MacGlintocMa seems, so far as we know, to be an extinct 

 and striking type which had a definite range in time, but many of 

 the plants associated with it have persisted to the present day almost 

 without modification. Still, their presence in England may be equally 

 indicative of a definite age of rock, though it would not do to extend 

 the use of their presence as standards of antiquity to strata in their 

 own existing habitats. Thus, Onoelea sensibilis represents a definite 

 stage in Mull, but as a United States fossil, where it still lives, we 

 cannot say that its occurrence proves strata to be contemporary with 

 those of Mull. So with Osmunda javanica, Chrysodium aureum, 

 Araucaria Cunninghami, Cryptumeria japonica, Taxodium disticlinm, 

 and many others, still living ; they mark a definite horizon here, or 

 period at which they flourished, and then disappeared, but in course of 

 their subsequent migrations they may have appeared in other countries 

 at quite different dates, and to draw comparisons as to the relative 

 ages of rocks from their presence in them might be most misleading. 



I have not been to Greenland, and I do not therefore know how the 

 plant-beds occur there. Some of the plants are identical with those of 

 the Antrim Basalts, some with those of Mull, and some with plants from 

 Lough Neagh. Whether these are from one horizon or from several I 

 do not know, but they are embedded in different qualities of rock, and 

 presumably therefore come from different levels. Not a shadow of 

 stratigraphical evidence has been brought forward for assigning them 

 to any particular stage of the Tertiaries, but it would seem natural to 

 classify them rather with the most tropical of the Eocene periods, that 

 of the London Clay, than with any other, as their presence so far 

 north, when so high a temperature prevailed in our latitude, presents 

 little or no physical improbability. The London Clay period was pre- 

 ceded in England by a relatively very temperate climate, and the 

 plant-beds of Greenland are preceded by an unfossiliferous zone, 

 marking a period when no floras were in existence so far north. 

 There is already abundant evidence that many plants and animals 

 passed from Europe to America by way of these high latitudes during 

 the Eocene, and evidence of every kind points to some of the plant- 

 beds at least being of early Eocene age. The Icelandic fossil plant- 

 beds I have ascertained to be on an altogether different and far newer 



