LAMELLIBRANCHIATA. 



Information with regard to the Molhiscan fauna of our North Atlantic islands was also obtained 

 from another side. The Icelandic botanist, Dr. Helgi Jonsson, who was dredging for algae at the 

 Faeroes and Iceland during the years 1897, 1898 and 1901, in response to ra}- request, preserved the 

 Molluscs collected at the same time and with great liberality presented them to the Zoological Museum 

 of Copenhagen University. His countryman, the zoologist Bjarni Scemundsson, has also assisted 

 me, among other ways, by lending material from the Natural Histor\- Collection at Reykjavik. 



A very considerable collection has been brought home from the Faeroes by Dr. Th. Morten sen, 

 who in 1899 carried out a series of dredgiugs from the gunboat "Guldborgsund" partly in the fjords, 

 partly on the banks down to a depth of ca. 150 fm. 



Lastly, Dr. Joh.s. Schmidt, the leader of the cruises with the research-steamer "Thor", has 

 during several years made collections at the Faeroes and Iceland and brought home a considerable 

 and very valuable material, from the littoral right down to the abyssal region, which he has preserved 

 for science by presenting it to the Zoological Museum of Copenhagen. 



For the sake of completeness I may further mention, that during my participation in the 1902 

 cruise of the research-steamer "Michael Sars" under the direction of Dr. J oh an Hjort, I was given 

 the opportunity of collecting a quantity of Mollusca on the banks round about the Faeroes, on the 

 east coast of Iceland as well as north and south of the Wyville Thomson Ridge. During ni}- voyages 

 in West-Greenland in 1906, 1908 and 1909 I also collected a great number of Molluscs. 



The present part of the work on the entire material will show, that my endeavours have been 

 directed first and foremost to the disentanglement of the species. The determinations have been made 

 as carefully as possible; that we can not be sufficiently critical regarding the determinations made 

 by our predecessors, even of common and apparently well-known species, I have alread\- shown in my 

 small papers on Mya and TclUiia. 



With respect to Greenland, I have restricted myself to give a brief review of the distribution, 

 as the works of Posselt and others have already discussed the details. For Iceland and the Faeroes, 

 on the other hand, each single place of occurrence has been mentioned, as there is a need here for 

 all the information we can obtain — better to have too much detail than the reverse. 



With regard to the synonym)' lists I may remark here, that they have been intentionally 

 divided into two sections, the first referring to the most necessary, systematic literature, wliilst the 

 second contains references to the principal, local fauna-lists. 



The region dealt with here — the "bridge" between Europe and America across the North 

 Atlantic Ocean and the slopes down to two deep-sea basins very different in hydrographical regards 

 — offers more than ordinary interest, and many and varied problems have presented themselves for 

 discussion as the work advanced. But the treatment of these and other conditions I shall postpone 

 meantime, until the systematic elaboration of the material is completed. 



Copenhagen, Zoological Miiscnni, 



October igii. Ad. S. Jensen. 



