odhner: marine mollusca of iceland. 29 



ern regions. A few specimens ha ve their principal distribu- 

 tion in the eastern districts, for example: Margarita striata, 

 Vejius fluctuosa and Bela angulosa, of which the lastnamed 

 is wholly lacking off Greenland. Other forms belong to the 

 western area; these are: Natica nana, Cerithiopsis costidata, 

 Bela Pingelii, Volutomitra groenlandica, Trophon craticulatus, 

 Philiyie qiiadrata and Mytilus edidis; thus more species show- 

 ing relation to the Greenland fauna. 



From the above statements the conclusion is to be drawn, 

 that Tceland is in faunistic respects most nearly related to 

 the arctic region and that its fauna is composed of both west- 

 ern and eastern elements. Besides these some southern con- 

 stituents have been assimilated with the fauna, these being 

 immigrated in a låter time and some of them a t present ex- 

 tinct again, and Iceland consequently proves in faunistic 

 respects, as in geographical, an intermediate district betvveen 

 the western, eastern and southern departements of the boreo- 

 arctic region. 



In some cases the measurements of the shells give the 

 same jesuits as to the relations of the fauna. Here only one 

 example of this fact may be pointed out. Margarita helicina 

 of south Iceland ( Ber uf jord) has a maximal diameter of 4,8 

 mm. Specimens from Spitzbergen are generally considerably 

 larger, their medium size amounting to 6—7 mm and their 

 maximum diameter to above 9 mm. Off Greenland both the 

 medium and the maximum size is somewhat higher than that 

 of the Iceland forms. The West-scandinavian species are in 

 contrary of a smaller size ; thus Margarita helicina of Iceland 

 in its measurements shows more resemblance to the western 

 and southern than to the north-eastern fauna. 



A further example of this kind is M. groenlandica. The 

 Iceland form has a greater resemblance to Norwegian and 

 Greenland specimens and it differs more from the forms 

 occurring off Spitzbergen. 



The present material is, however, too incomplete to allow 

 quite certain conclusions in faunistic respects, and more de- 

 tailed investigations must be carried out before the problem 

 of the relations and the origin of the Iceland fauna can be 

 conclusively decided. 



