The relationship between the palaeartic and nearctic faunas 237 



the distribution of which could not be explained either by active or passive oversea 

 dispersal or as a relict of a former circumpolar area. 



Besides Cepaea hortensis, 0kland (1927, p. 353-355) regards three species of 

 terrestrial Arthropods as primary Amphiatlantic: the Wood-louse Oniscus asellus 

 L. and two Ground-beetles of the genus Carabus, nemoralis Miill. and problema- 

 ticus Hbst. {catenulatus auctt.). The two first mentioned, without any doubt, are 

 European introductions into North America; the proposed endemic North Ameri- 

 can form of Carabus nemoralis is a fiction {vide Lindroth, 1955 a, p. 27), and the 

 records of Carabus problematicus, as "sbsp. californicus Mtsch.", from western 

 North America are based on specimens with wrong locality labels {vide Lindroth, 

 1954a, p. 46). 



There are a few more Eur- American animals, belonging to different taxonomical 

 groups, which have a more or less pronouncedly Amphiatlantic distribution but 

 which may be explained either by insufficient knowledge of the actual area and/or 

 by early introduction with man into North America. Instances are the Click- 

 beetle {Elateridae) Corymbites sjaelandicus Miill., the Moth {Noctuidae) Amphipyra 

 tragopogonis L., the Spiders Gonatium rubens Blackw. and Haplodrassus signifer 

 C. L. Koch, and the Snail Vallonia excentrica Sterki. These are to be found among 

 species preceded by a cross in brackets (f) in the list given in Chapter I. 



"Westarctic" species 



The concepts "Westarctic" and "Amphiatlantic" overlap, and certain members 

 of the first-mentioned group were enumerated above (and marked with a "W") 

 among the Amphiatlantic species.' The name "Westarctic" was, however, given 

 from a Scandinavian point of view^ in order to cover species of a northern or 

 alpine character with affinities towards the west, to North America. The word was 

 created by Th. Fries (1913) on a botanical basis and was soon applied to insects 

 {Lepidoptera) by Wahlgren (1919). For more recent views on Westarctic plants, 

 the reader is referred to Hansen (1929, p. 224 a.f.), Nordhagen (1935, p. 143 a.f.), 

 and Nannfeldt (1940, p. 39). 



The definition of a Westarctic plant or animal is that its occurrence in north- 

 western Europe (Fennoscandia) is cut off towards the east but more or less con- 

 nected with an area in North America by means of occurrences in Greenland, pos- 

 sibly also in Iceland and/or Spitzbergen. The concept i not merely a descriptive 

 one, it contains implicitly the idea that these organisms have reached Fennoscandia 



^ In North America this group would be termed "Eastarctic"! 



