102 TB. GWTN JEPrBETS ON 



The stream and drift currents of the Atlantic and Pacific Oceans, 

 with the surface temperature, are, indeed, most carefully laid down 

 in the ' Pilot Charts ' which have been lately published by our 

 Admiralty under the superintendence of its eminent Hydrogra- 

 pher ; but the direction and force of the abyssal currents ought to 

 be fully investigated before we can explain the distribution of deep- 

 water Mollusca, especially of the bivalves and such of the uni- 

 valves as cannot swim, and whose fry do not rise to the surface 

 and become for a short time oceanic. Voluntary migration seems 

 to have little, if any, share in the work of diifusion. It is to be 

 hoped that the present expedition of H.M.S. ' Challenger ' will 

 contribute much information on this very important and interest- 

 ing subject, in the same way that to a limited extent was done in 

 the ' Porcupine ' expeditions. It is difl&cult to account for the 

 occurrence of so many of the same species in the seas of Japan 

 and the North Atlantic Ocean. Probably those species which 

 inhabit deep water may have had a common origin or birthplace 

 in high northern latitudes, and have found their way to Japan on 

 the one side and Europe on the other by means of a bifurcation 

 of the great Arctic current. Their entry into the Mediterranean 

 from the Atlantic may have taken place through a wide channel 

 which formerly existed between the lower part of the Bay of 

 Biscay and the Grulf of Lyons, and which has been satisfactorily 

 shown on geological grounds to have been made since the Ter- 

 tiary epoch. The present communication through the Straits of 

 G-ibraltar seems to be also of a comparatively modern date. 



With respect to the fishes which are common to Japan and 

 the Mediterranean or the North Atlantic, I have been favoured 

 by Dr. Albert Griinther, P.R.S., with a list and note, which, with 

 the permission of the Society, I will append to this paper. His 

 authority as an ichthyologist is so great that his communication 

 will be valuable on its own account, as well as in showing the 

 distribution of the species not only among the invertebrates but 

 also in the vertebrate fauna in the northern divisions of the 

 Atlantic and Pacific Oceans. 



Subkingdom MOLLUSCA. ' 

 Bbachiopoda. 



Rhynchonella psittacea, Gmelin ; young. 



35 fathoms. Lat. 41° 41' N. ; long. 141° 0' E. Circumpolar. 



