238 REPORT 1868. 



Canal, which extends from one coast to the other, and is very little ahove 

 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 fathoms, 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, Eabr.) 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 remarkable 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 second volume of * British Conehology,' p. 58 ; and he 

 seems to have 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 be seen in full force 

 on the North American continent ten or more degrees further south than in 

 Europe." Possibly he was misled by one of Forbes's conclusions (Rep. Geol. 

 Surv. p. 402), that " no glacial beds are known in Southern Europe." This, 

 however, was more than twenty years ago. I have myself identified from 

 the Calabrian and Sicilian deposits several high-northern shells (e. g. Tere- 

 bratula cranium, T. septata, Lima excavata, Mytilm modiolus, Ci/prina Islan- 

 dica, Mya truncata, var. Uddevallensis, Saxicava Norvegica, Puncturella Noa- 

 china, Emarginula crassa, Buccinum undatwn, and Natica affinis or clausal), 

 and from the Rhodian deposits Terebratula septata and Lima Sarsii. 



My old companion, Mr. Waller, picked up on the beach in a small bay on 

 the west coast of Shetland a shell of Spirula australis. It is a tropical 

 Cephalopod, and is not unfrequently thrown up by the waves on the southern 

 and western shores of England, Wales, and Ireland, together with exotic 

 species of Teredo, lanthina, and Hyalcea brought from southern latitudes. 

 Dr. Morch informs me that several shells of the Spinda have this year been 

 found in the Earoe Isles. The transport of such tropical productions to 

 northern latitudes has been usually attributed to the Gulf-stream. It now, 

 however, appears more probable that this is the consequence, not of the direct 

 action and course of the Gulf-stream, but of the prevalence of westerly and 

 south-westerly winds, which waft onwards to northern latitudes, in a north- 

 erly and north-easterly direction, the floating objects carried .to a certain 

 distance by the Gulf-stream. The direct course of the Gulf-stream has not 

 been observed further north than about 45 N. lat. ; from that point it would 

 seem to dwindle into a north-easterly surface drift. A chart will shortly be 

 published by the Admiralty in explanation of this view of the case ; and the 

 following papers on the subject ought to be consulted by physical geographers : 

 Dr. Stark " On the Temperature of the Sea around the coasts of Scotland 

 during the years 1857 and 1858, and the bearing of the facts on the theory 

 that the mild climate of Great Britain during winter is dependent on the 

 Gulf-stream " (Trans. R. S. Edin. 1859), and Capt. Thomas's tables and re- 

 marks in Mr. Alex. Buchan's Report " On the Temperature of the Sea on 

 the Coast of Scotland" (Journ. Scottish Meteor. Soc. Oct. 1865). See also 

 <Br. Conch.' vol. i. (Introd.) pp. xeviii and xcix. 



I will add a short summary of the observations recorded in my Reports on 

 Shetland drcdgings and in the work last cited. 



1. The bathymetrical zones have been too much divided by Risso and sub- 

 sequent authors. There are two principal zones, littoral and submarine ; the 

 nature of the habitat and the supply of food influence the residence and mi- 



