odhner: marine mollusca of iceland. 27 



Thus most of the forms, that may be named as boreal 

 or at least not high-arctic, are found on the west and the 

 south coasts of Iceland, at Reykiavik and Berufjord, such as 

 Nacella pellucida, Lacuna pallidula, Onoha acideiis, Älvania 

 scrohicidata, Skenea planorbis, Limatula siihaiiriculata, Cyamiimi 

 miiiutum and others. 



Some of these more temperate forms, however, also ocour 

 on the north coast, and in this respeet an especially remar- 

 kable locahty is met with in Thistilfjord (with Raufarhofn). 

 Though this fiord is situated in the NE part of the island, 

 where the temperature of the sea is relatively low through 

 the brancli of the Gulf Stream, setting in from the west, just 

 ending at this district and being succeeded by an arctic 

 current, that often blocks the north coast with drift-ice, we 

 find here a good many more temperate molluscs, namely 

 Tectura virginea, Onoba acideus and striata, Skenea planorbis, 

 Anomia aculeata, Limafula subauriculata, Cardium fasciatum, 

 Mactra ellipiica, and Cyprina islandica besides a more infJa- 

 ted variety of the last shell. 



Of such forms there are also found a few in other loca- 

 lities on the north coast, e. g. Onoba striata in Öfjord, Buc- 

 cinum undatum in Siglafjord and Cardium fasciatum and Ano- 

 711 ia ephippiufn in both these fiords. 



The cause of the occurrence of such a number of south- 

 ern mollusca a t the north eastern part of Iceland, is hardly 

 to be looked for in the present hydrographical states, which 

 are not favourable for the existence of the named species at 

 this place; therefore they must be assumed as constituting a 

 relic fauna, that has had a wider distribution during a 

 warmer period, from which it has been left here, isolated 

 from the environments. If there are any grounds for this 

 supposition, it may also be possible, that other southern forms 

 on the north coast, such as Cardium fasciatum, are of a relic 

 nature too. There are some facts seeming to support this 

 assumption about the fauna of Thistilfjord. The named spe- 

 cies, which are distributed on tho southern and western 

 coasts of Iceland, ha ve their northern limits in Norway with- 

 in the arctic region, in Finmarken. But there the influence 

 of the Gulf Stream is considerably higher than on the north- 

 eastern Iceland coast. This circumstance makes it probable 

 that the mollusca in question might be immigrated here 



