38 AUGUSTA ÄRNBÄCK-CHRISTIE-LINDE, NORTHERN AND ARCTIC INVERTEBRATES. 



General Distribution. 



P. libera has been collected, though a few specimens only, on the coast of Nor- 

 way: in Komagefjord, Öxfjord, off Vadsö (ef. Kiaer 1893); at Gaasvaer off Tromsö, 

 300 m; in Porsangerfjord; in Vestfjord off Bodö, 105—160 m; W. of Aalesund; in 

 the North Sea; N. of the Faroe Islands (Bjerkan 1905, 1908); in the North Atlan- 

 tic, depth, 836 m (Bonnevie 1896). One specimen has been reported from Spitz- 

 bergen: King Charles Land (Hartmeyer 1903), and 10 specimens have been dredged 

 off West Taimyr, Nansen Island, 18 — 30 m (Redikorzew 1910). 



Remarks. 



If we compare the descriptions of the following four species of Polycarpa: P. 

 libera Kiaer, P. comata Ålder, P. pusilla Herdman, P. fibrosa Stimpson, it is 

 evident that they are closely allied forms and it seems dubious whether they are 

 distinct species. 



According to Hartmeyer (1903, p. 228), P. comata and P. libera cannot be 

 regarded as synonymous species, owing to differences in the internal strueture: the 

 number of tentacles, the dorsal tuberele, the branchial sac, and the alimentary canal 

 do not agree. The geographical distribution, too, is different, P. comata being con- 

 fined to the coasts of western Europé. Michaelsen, however, who has found an 

 intermediate individual from the coast of Portugal, has united the two species under 

 the name of P. comata (1911). Låter (1912) the first-mentioned author has discussed 

 the difficult question again without answering it definitively. Van Name (1912) is 

 of opinion that it is not unlikely that P. libera Kiaer is identical with P. fibrosa 

 which occurs on the north-eastern coast of N. America from the Gulf of St. Law- 

 rence to Nantucket. 



As I have not had any opportunity of re-examining and comparing the species, 

 the question must be left open. It should only be pointed out that, if the three 

 species in question would prove to be identical, which seems most probable, the 

 name should be P. fibrosa which, as far as I can see, has priority, having been 

 used by Stimpson in 1852. 



Only a few specimens of Pohjcarpa libera are at present known from the 

 Arctic region and they have been dredged at three localities: West Taimyr, King 

 Charles Land and East Greenland. Its distribution extends, along the north- 

 western coast of Norway, into the Boreal region where it is not rarely met with 

 off the coast of Bohuslän especially in Gullmarfjorden. If it would prove to be 

 identical with P. fibrosa and P. comata its range within those southern zones should 

 be wider, comprising the coasts of western Europé, where P. comata occurs, and the 

 north-eastern coast of N. America where P. fibrosa is abundant. 



Polycarpa libera is generally found on bottoms of clay or on muddy bottom 

 with sand and stones. In Norway and the N. Atlantic it has been dredged from 

 considerable depth, from 60 down to 836 m, in the Arctic Sea of Siberia from more 



