28 ARKIV FÖR ZOOLOGI. BAND 7. N:0 4. 



during a period with a warmer climate than at present, and 

 similar to tbat of the norvvegian north coast nowadays. 



The opinion of a maximum of climate is quite consi- 

 stent with the conclusions drawn by Bårdarson on the 

 basis of geological investigations. He has shown that some 

 Southern mollusca, such as Purpura lapilhis, Zirphcea cris- 

 paia and Gyamium minutum, living at present only in the 

 western coast-districts, occur in a fossil state in some north- 

 ern fiords. From this fact he has concluded a higher tem- 

 perature during the corresponding period. 



The fauna of Thistilfjord is consequently in all probabi- 

 lity a remnant from this time. 



Besides the fact that some southern mollusca are living 

 on northern parts of Iceland, the western and southern coasts 

 are, on the other hand, remarkable for the ab-ence or the 

 rareness of some northern forms, above all Pecten islandicus, 

 a fact, that is also pointed out by Bårdarson. To the same 

 group might be referred M argarita Valilii, Naiica nana, Scala- 

 ria groenlandica, Volutomitra groenlandia, Cerithiopsis costidata, 

 and Thracia septentrionalis, all these with the main distribu- 

 tion off Greenland, and probably also Trophon craticulatus, 

 Buccinum tenue, Cardium groenlandicum and others. 



Of such northern forms many occur in Berufjord on the 

 south coast, a district, which thus proves to have a fauna of 

 mixed character. Whether its northern constituents have 

 been added by the influence of the present hydrographical 

 conditions or they are perhaps to be explained by the assump- 

 tion of a cooler period from which they should be relics, this 

 is a question, which at present it is unable to answer. 



This short paper is not the place to compare exhausti- 

 vely the fauna of Iceland with that of other northern districts. 

 But some facts are of such interest as to be worthy of atten- 

 tion. The fauna comprises a good many species with a wide 

 distribution, belonging to the genera Boreochiton, Puncturella^ 

 Lunatia, Leda, Tellina, Saxicava and others, in all about 40 

 species. Besides these there are some forms which are ejse- 

 where found only in southern districts: Nacella pellucida, 

 Tectura virginea, Gibbida tumida, Cijprina islaiidica etc, but 

 these amount only to 10 a 15 species. On the other hand 

 many species have their principal distribution in the arctic 

 area, of which ca 40 occur both in the western and the east- 



