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nutus and Eurycercus glacialis. The distribution of these species is 
northern. In Iceland they have all their optimum in gr. III (the 
coldest part of the island). 
The Iceland species with a predominant Southern distribution 
occur only scarcely and with optima in the lowland (gr. I), while 
the five arctic species named above are found in large quantities. 
The Icelandic fauna of Entomostracians is arctic-sub- 
arctic. 
In other arctic and subarctic countries the Entomostracians here 
dealt with are found in the following number of species. 
High-Sweden 45. Greenland 32. 
Jamal. 39. Iceland . . 32. 
The reason why Iceland and Greenland have a lower number 
of species than High-Sweden and Jamal is surely due to the faet 
that the possibilities of immigration are far smaller for Iceland 
and Greenland than for High-Sweden and Jamal. To the former 
countries the immigration can only be passive, while for the latter 
it can also be active. 
In Iceland (as well as in Greenland) no endemic species are 
found. On the whole the Entomostracians are widely spread, which 
is in good accordance with the faet that the Sub-class geologically 
seen is an old one. 
Of the Diaptomidae, the most locally distributed family of the 
Entomostracians, a nearctic species {Diaptomus minutus) and a palæ- 
arctic species {Diaptomus glacialis) are found in Iceland. The im¬ 
migration has thus taken place both from America and from Europe. 
Iceland has besides 24 species in common with Europe and 22 with 
Greenland. With regard to the Entomostracians Iceland 
must therefore be said to be a boundary where the 
faunas of the old and the new world are meeting 
each other. 
