among the Shetland Isles. 303 
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. Terebratula cranium, T. sep- 
tata, Lima excavata, Mytilus modiolus, Cyprina Islandica, Mya 
truncata, var. Uddevallensis, Saxicava Norvegica, Puncturella 
Noachina, Emarginula crassa, Buccinum undatum, and Natica 
affinis or clausa), and from the Rhodian deposits Terebratula 
septata and Lima Sarsit. 
My old companion, Mr. Waller, picked up on the beach in 
a small bay on the west coast of Shetland a shell of Sprrula 
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 Hyalea brought from southern latitudes. 
Dr. Mérch informs me that several shells of the Spzrula have 
this year been found in the Faroe 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 northerly and north-easterly direc- 
tion, 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. 
xevill and xcix. 
I will add a short summary of the observations recorded in 
my Reports on Shetland dredgings and in the work last cited. 
1. The bathymetrical zones have been too much divided by 
Risso and subsequent authors. There are two principal zones, 
21* 
