The relationship between the palaearctic and nearctic faunas 



FIG. 32. Distribution of the Staphylinid beetle Micralymma 

 marinum Strom {stimpsoni Lee), inhabiting the tidal zone, in 

 relation to the Gulfstream. The figured specimen is from 

 Newfoundland. 



(From LiNDROTH, 1931, revised.) 



(Photo P. Ardo.) 



4. A fourth group would consist of warm-blooded animals, active in winter 

 and therefore possibly able to traverse the sea between arctic islands and continents 

 on the ice. This group is well represented among Circumpolar (p. 291), but not 

 among Amphiatlantic animals, except perhaps once, temporarily, by the Muskox 

 (Ovibos moschatus L.) (vide map by Ekman, 1922, p. 396). 



5. Freshwater species with stage of development adapted to passive transport 

 with birds. The Sponge Heteromeyenia ryderi. Like others of the fresh-water 

 Spongillids, this species forms "gemmulae", less than i mm. in diameter, which 



