TRANSACTIONS OF SECTION E. 803 



very much wider range tlian those of Mesozoic and latei" ages, and were characterised 

 above all by the presence of many cosmopolitan species, and we can hardly resist 

 the conclusion that it was the comparative shallowness of the ancient sea8 that 

 favoured that wide dispersal of species, and enabled currents to distribute sedi- 

 ments the same in kind over such vast regions. As the oceanic area deepened and 

 contracted, and the land surface increased, marine faunas were gradually restricted 

 in their range, and cosmopolitan marine forms diminished in numbers, while sedi- 

 ments, gathering in separate regions, became more and more diflerentiated. ]<"or 

 these and other reasons, which need not be entered upon here. I see no necessity for 

 supposing that a Palreozoic Atlantis connected Europe with North America. The 

 broad ridge upon which the Fserije Islands and Iceland are founded seems to 

 pertain as truly to the oceanic depression as the long Dolphin Ridge of the Soutli 

 Atlantic. The trend of the continental plateau in high latitudes is shown, aa I 

 think, by the general direction of the coast-lines of North-western Europe and East 

 Greenland, the continental shelf being submerged in those regions for a few hundred 

 fathoms only. How the Icelandic ridge came into existence, and what its age may 

 be, we can only conjecture. It may be a wrinkle aa old as the oceanic troufrh 

 which it traverses, or its origin may date back to a much more recent period. We 

 may conceive it to be an area which has subsided more slowly than the floor 

 of the ocean to the north and south ; or, on the other hand, it may be a belt of 

 positive elevation. Perhaps the latter is the more probable supposition, for it 

 seems very unlikely that crustal disturbances, resulting in axial and regional 

 uplifts, should have been confined to the continental plateau only. Ba that as it 

 may, there is little doubt that land connection did obtain between Greenland 

 and Europe in Cainozoic times, along this Icelandic ridge, for relics of the same 

 Tertiary flora are found in Scotland, the Fieroe Islands, Iceland, and Greenland. 

 The deposits in which these plant-remains occur are associated with great sheets 

 of volcanic rocks, which in the FseriJe Islands and Iceland reach a thickness of 

 many thousand feet. Of the same age are the massive basalts of Jan Mayen, 

 Spitzbergen, Franz Joseph Land, and Greenland. These lavas seem seldom to 

 have issued from isolated foci in the manner of modern eruptions, but rather to 

 have welled up along the lines of rectilineal fissures. From the analogy of similar 

 phenomena in other parts of the world it might be inferred that the volcanic action 

 of these northern regions may have been connected with a movement of elevation, 

 and tliat the Icelandic ridge," if it did not come into existence during the Tertiary 

 period, was at all events greatly upheaved at that time. It would seem most likely, 

 in short, that the volcanic action in question was connected mainly with crustal 

 movements in the oceanic trough. Similar phenomena, as is well known, are met 

 with further south in the trough of the Atlantic. Thus the volcanic Azores rise 

 lilce Iceland from the surface of a broad ridge which is separated from the conti- 

 nental plateau by wide and deep depressions. And so again, from the back of the 

 great Dolphin Ilidge, spring the volcanic islets of St. Paul's, Ascension, and Tristan 

 d'Acunha. 



I have treated of the Icelandic bank at some length for the purpose of sbowincr 

 that its volcanic phenomena do not really form an exception to the rule that such 

 eruptions ceased after Palreozoic or early Mesozoic times to disturb the Atlantic 

 coast-lines of Europe and North America. As the bank in question extends 

 between Greenland and the British Islands, it was only natural that both those 

 regions should be affected by its movements. But its history pertains essentially 

 to that of the Atlantic trough ; and it seems to show us how transmeridional 

 movements of the crust, accompanied by vast discharges of igneous rock, may come 

 in time to form land connections between what are now widely separated areas. 



Let us next turn our attention to the coast-lines of the Gulf of Mexico and the 

 Caribbean Sea. These enclosed seas have frequently been compared to the Medi- 

 terranean, and the resemblance is self-evident. Indeed, it is so close that one may 

 say the Mexican-Caribbean Sea and the Mediterranean are rather homologous than 

 simply analogous. The latter, as we have seen, occupies a primitive depression, 

 and formerly covered a much wider area. It extended at one time over much of 

 Southern Europe and Northern Africa, and appears to have had full communica- 



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