ATLANTIC COXTIXKXT. 225 



suppose that during the Miocene epoch there was an extension 

 of an Atlantic continent from the Arctic zone far towards the 

 south, so as to unite America and Europe, from Iceland to the 

 United States of North America *. Such an Atlantic continent 

 would account for the fact that, of 56 species of Miocene plants 

 that Prof. Heer knows from Alaska f, 17 occur in the Swiss 

 Miocene flora. In this number there are 3 species of poplar, 

 3 willows, the liquidambar, a walnut, &c. Under these circum- 

 stances it may be understood how the planes and the sabal 

 palm established themselves everywhere in Europe, how the 

 tulip-tree migrated into Iceland and Switzerland, and how Swiss 

 fossil remains comprise gigantic frogs, long-necked tortoises, 

 Belastomata, and Gyrlm, such as are now only to be met wfth 

 in American waters. 



The hypothesis of an Atlantic continent would explain in a 



* The objection urged, that this Atlantic continent would have occupied 

 nxactly the deepest parts of the ocean, is not well founded ; for the greatest 

 depth of the ocean occurs much further south, namely between Southern 

 Africa and South America. The greatest breadth of this continent would 

 correspond to the line of the- transatlantic telegraph, which lies at a mean 

 depth of 0-439 of a geographical mile. The identity of the Miocene corals of 

 the south-west of Europe with those of the Antilles is a proof of the exist- 

 r-nce of shallow shores running from one continent to the other, as the corals 

 will not build in a deep sea. If the southern shores of the supposed Atlantis 

 were fringed with coral-reefs, such as are now met with in the Miocene 

 rif Porto-Santo, the identity between the coral fauna of Miocene Europe and 

 that of America is easily explained, whilst if the two continents were sepa- 

 rated by a vast and deep sea this explanation would be very difficult (see 

 the 'Flore Fossile des pays arctiques,' by Prof. Heer, i. p. 52). 



f Dr. Newberry has just discovered several species which belong in com^ 

 mon to the Miocene of Fort Union, Dacotah, and to that of Europe, e. g, 

 Onoclea semibilis, Linn. (Filirites hebridicus, Forbes, from the island of Mull), 

 Olyptostrobus enropceus, and a fan-palm very nearly allied to the Sabal major. 

 The Arctic zone having been, in Miocene times, a very important vegetable 

 focus from which plants could spread in all directions, many species probably 

 had from thence their origin, such as the Taxodium, Sequoia Lanysdorfii, 

 Glyptostrobus, and others. It is not unimportant to observe that the species 

 common to the Swiss Miocene flora and to that of North America are especi- 

 ally species of the temperate zone j these species probably originated in the 

 North. Nevertheless tropical forms are not wanting ; but such plants as the 

 sabal palm could not come from Arctic countries. 



VOL. IT. Q 



