THE PLIOCENE BEDS OF ST. ERTH. 209 



The tract of land between the mouth of the Garonne and Per- 

 pignan attains a maximum elevation of 600 feet, according to Prof. 

 Prestwich*, who quotes M. Yirlet d'Aoust, to the effect that Pliocene 

 beds occur on the ^Xlediterranean slope at an elevation of 540 feet. 



Dr. Gwyn Jeffreys remarkedf : — " I, however, fully agree .... 

 that at some former period .... there was an open communication 

 between the Atlantic and the Mediterranean by which the fauna 

 became diffused. I should be inclined to place the Atlantic point 

 of communication at Bordeaux, and that of the Mediterranean at 

 Narbonne, in the line of the Languedoc Canal, which extends from 

 one coast to the other, and is very little above the present level of 

 the sea. This communication must have been very wide, and it re- 

 mained open during the Glacial epoch, which affected not only the 

 N. of Europe, but also Naples, Sicily, and probably Rhodes." The 

 Straits of Gibraltar appear to have been closed during the late 

 Pliocene times. 



Many recondite problems concerning the present and past distri- 

 bution of life will, we think, be elucidated by the application of 

 these hypotheses ; and to one or two of these we may perhaps be 

 permitted to refer, while others must be reserved for consideration 

 in a future paper. 



The speculations of the late Edward Forbes regarding a former great 

 western extension of the continent should, we think, be carefully 

 examined in connexion with the subject of which we are treating ; 

 but it would be foreign to our present purpose to do more than draw 

 attention to them and suggest the propriety of such an inquiry. 



His (Forbes's) theory was that a continuous or only slightly inter- 

 rupted land-surface extended from Ireland to Spain in late Tertiary 

 times, permitting of the free migration of Spanish plants to Ireland, 

 where about 20 species still survive. 



The western shores of this land he placed along the line of the 

 Sargasso Weed. 



Much additional evidence in favour of this view is to be obtained 

 from the study of the distribution of Recent Mollusca, both marine 

 and terrestrial, in the Azores, Canaries, and on the western shores of 

 the Spanish Peninsula. 



The position of the beds at St. Erth shows that some considerable 

 movements have taken place subsequently to their accumulation ; 

 thus the beds occur at an altitude at least 200 feet above their 

 original position of deposition, and dip about 5° to the N.jST.W. 



The movement which raised them was clearly not one of equal 

 elevation, otherwise they would have no dip ; so that it seems safe 

 to assume that it was an undulatory or tilting movement, like in 

 kind, though in less degree, to that now affecting the Scandinavian 

 peninsula. 



Reversing this movement to restore the beds to their original 

 position, we should have a broad gulf at St. Erth and to some 

 distance eastward. The fulcrum would be about 1 mile to the W. ; and 



* Quart. Journ. Geol. Soc. vol. xxvii. 

 t Shetland Keport, Brit. Assoc. 1868. 



