of British Mollusca. 453 



Association of the United Kingdom ; and there was also some 

 good trawling off the south-west of Ireland, conducted during 

 a week's cruise in a hired steamer, the ' Flying Fox,' by the 

 Rev. W. Spotswood Grceiij the deepest trawl being in 1000 

 fathoms. 



In all these expeditions Mollusca have been found either 

 hitherto undescribed or not before known to exist in the sea 

 around the British Islands. 



Dr. Gwyn Jeffreys was at the time of his death engaged in 

 publishing a series of papers in the ' Proceedings of the 

 Zoological Society ' on the Mollusca obtained in the more 

 important of these expeditions. He died before these papers 

 were finished, and we therefore still remain in ignorance of 

 what was found among many families of the Gastropoda. It 

 is to be hoped, however, that Mr. E. A. Smith will before 

 long complete the work with the help of MS. left by Jeffreys 

 and such specimens as are in the British Museum. 



Reference is, however, made in various papers publishe I by 

 Dr. Jeffreys to species of those families which were procured 

 in the i Porcupine ' expedition. My friend, had his life been 

 prolonged, would have drawn up a fresh list of the Mollusca 

 which inhabit the British area. In attempting to do this now 

 I shall have to mainly rely in the earlier part of this revision 

 upon notes scattered through Dr. Jeffreys's various papers, 

 while for the rest his account of " The Mollusca procured 

 during the ' Lightning ' and 'Porcupine' Expeditions" will 

 supply the chief material as regards the deep-sea fauna. 



It may be stated with respect to my purpose and revision 

 generally — 



1. That there were many cases of nomenclature adopted in 

 ' British Gonchology ' with which I felt unable to agree at the 

 time of its publication and am equally unable to acquiesce in 

 now. 



2. Many works have since been published, and the light 

 which has been thrown from many sides on groups of Mol- 

 lusca necessitates numerous alterations in nomenclature and 

 arrangement. 



3. Many recent malacological investigators of the Ptero- 

 poda (Boas, Pelseneer, Grobben, &c.) are agreed that these 

 Mollusca should not be maintained as a distinct Class, but 

 rather as an order or as families of the Gastropoda. That 

 view is here followed. 



4. Jeffreys not having studied the Nudibranchiate Mol- 

 lusca requested Mr. Alder to draw up the account of that 

 order. As Mr. Alder did not give the geographical distribu- 

 tion of the species, I have supplied this as far as I am able. 



