272 С. H. Ostenfeld. 



in others they stand intermediate and in others again they were 



typical (fig. 127 c); thus the f. atlaniica has probably a very restricted 



value. 



Distrib. Arctic neritic species; known from tlie coasts of arctic coun- 

 tries; also (rarely) found at Boliuslen, Scotland and in the Norwegian Sea. 



Chætoceras Ehrbg., 1844. 



20. Chætoceras atlanticum Cleve, Bib. K. Svenska Vet. Akad. 

 Handl., Bd. I, No. 13, lcS73, p. 11, pi. 2, fig. 8 ; Gran, Nord. Plankton, XIX, 

 1905, p. 64, fig. 74. 



This species is found in several samples from Danmarks Havn, 

 the coast water and the pack-ice, but always in single specimens. 

 July-September 1906-1908. 



Distrib. Widely distributed in the Atlantic Ocean and its tributaries, 

 also in the Antarctic Ocean; oceanic species. 



21. Chætoceras convolutum Castracane, Report of the Challenger 

 Exp., Botany, II, 1886, p. 78; Gran, Fauna Arctica, III, Heft 3, 1904, 

 p. 530, fig. 1 ; Nord. Plankton XIX, 1905, p. 69. 



In the pack-ice this species was dominant in some samples from 

 August 1906; in 1908 it was also present, but not in greater quan- 

 tities. It was further found in samples from the coastal water and 

 from Danmarks Havn, but only sporadically and in single specimens. 



Distrib. Northern oceanic species, known from the Nortli Atlantic 

 and the Antarctic Oceans. 



22. Chætoceras criophilum Castracane, Report of the Challenger 

 Exp., Botany, II, 1886, p. 78; Gran, Fauna Arctica, III. Heft 3, 1904, 

 p. 532, fig. 3; Nord. Plankton XIX, 1905, p. 71. 



If we follow Gran (1. c.) in the distinctive marks between this 

 and the foregoing species, i. e. С criophilum has none or a very 

 rudimentary connecting zone and С conuolatum a v,'ell developed 

 one, it results that this species is very rare in the area, only some 

 solitary specimens were found in two samples from the pack-ice, one 

 in 1906 and one in 1908. It is rather unexpected that it is so rare, 

 as it is one of the characteristic and dominant species of the sea 

 between Iceland and Jan Mayen. 



Distrib. Northern oceanic species, widely distributed in the northern 

 parts of the Atlantic and its tributaries, further known from the Antarctic. 



23. Chætoceras boréale Bailey, Smitsonian Contrib. to know- 

 ledge, vol. 7, 1854, p. 8, figs. 22 — 23; Gran, Fauna Arctic. Ill, Heft 3, 

 1904, p. 533, fig. 5, Nord. Plankton XIX, p. 73. 



One of the most common species in the area. Both in 1906 

 and 1908 it was the dominant species in many samples from the 



