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. 1. 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 Aigean”’ 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 [ am not a believer in ‘ repre- 
sentative forms.’’ He evidently was not aware of the fact 
that boreal (not arctic) species still live im 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 Rhodes. 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 Spirorbis (S. cancellatus, Faby.) 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, 
im 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. 1. p. 298) 
that “ deposits filled with arctic species of marine shells are to 
