302 Mr. J. Gwyn Jeffreys on Dredging 



How is this concordance to be accounted for ? I have care- 

 fully read again Forbes's elaborate essay '^ On the Connexion 

 between the distribution of the existing Fauna and Flora of 

 the British Isles, and the Geological changes which have 

 affected their area, especially during the epoch of the Northern 

 Drift " (Memoirs of the Geological Survey of Great Britain, 

 vol. i. 1846) ; but I cannot find in it a satisfactory solution of 

 the question. He, indeed, mentions the continuance of some 

 " arctic" species in the British seas, the rest having "retired 

 for ever," and that certain other species which he called 

 " Boreal or Celtic " occurred in a fossil state in Sicily ; and 

 he states (p. 390) that " in the deepest of the regions of depth 

 in the ^gean " the same representation of a northern fauna as 

 exists in our own seas is maintained, " partly by identical and 

 partly by representative forms." The instances he gives do 

 not support such a view ; and I am not a believer in " repre- 

 sentative forms." He evidently was not aware of the fact 

 that boreal (not arctic) species still live in the Mediterranean. 

 I, however, fully agree with him that at some former time 

 (which he designates "the newer pliocene epoch") there was 

 an open communication between the Atlantic (according to 

 him the "North Seas") 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 remained open during the 

 glacial epoch, which affected not only the north of Europe 

 but also Naples, Sicily, and probably Ehodes. Dr. Tiberi 

 showed me a fine valve of Pecten Islandicus which had lately 

 been fished up in the Gulf of Naples at a depth of 50 fa- 

 thoms, and with it a valve of P. opercularis quite as large as 

 northern specimens ; both the valves were in a semifossil state, 

 and the former was covered with the same Greenland species 

 of Spirorhis {8. canceUatus, Fabr.) as I noticed on valves of 

 P. Islandicus dredged in the Shetland seas at depths varying 

 from 75 to 170 fathoms. Sir Charles Lyell has not adverted, 

 in the last edition of his '■ Principles of Geology,' to the re- 

 markable occurrence of such glacial fossils in the Shetland 

 sea-bed, to which I called the attention of geologists in my 

 former Reports as well as in the 2nd volume of ^ British Con- 

 chology,' p. 58 ; and he seems to have strangely overlooked 

 the observations of Philippi and Seguenza on the fossils of 

 Calabria and Sicily, when he stated (Princ. Geol. i. p. 298) 

 that " deposits filled with arctic species of marine shells are to 



