Marine Plankton from the East-Greenland Sea. 271 



Rhizosoleuia (Ehrbg.) Brightw. 1858. 



16. Rhizosolenia styliformis Brightw., Quart. Journ. Microsc. 

 Science, VI, 1858, pi. V, fig. 5; Peragallo, in Le Diatomisle, vol. I, 1892, p. 

 Ill, pi. 4, figs. 1—5; Gran, Rep. Nonveg. Marine- and Fishery-Investig., 

 vol. 2, No. 5, 1902, pi. 1, figs. 1—9; Nord. Plankton, 1905, XIX, p. 54. 



Found in Danmarks Havn (September— October 1906, August 

 1907) and in the coastal water (1906 and 1908), but nearly absent 

 from the pack-ice. It occurs in most samples very rarely, but in 

 a single one not uncommon. 



D i strib. Widely distributed oceanic speeies. often character organism 

 over large areas of water, mostly a temperate species, but here and in some 

 other exceptional cases behaving as an arctic organism. 



17. Rhizosolenia hebetata Bailey, American Journ. of Sc. and 

 Arts, Ser. 2, vol.22, 1856, pi. 1, figs. 18, 19; Cleve, Vega-Exp. vetensk. 

 iakttag., Bd. 3, 188.3, pi. 6, fig. 69; Gran, Fauna Arctica, Bd. 3, Lief. 3, 

 1904, p. 524; Nord. Plankton 1905, XIX, p. 55, fig. 67. 



f. semispina (Hensen) Gran, 1. c, p. 55; Rh. semispina Hensen, 

 V. Ber. Komm. Unters. Deutschen Meere, 1887, p. 84, pi. 5, fig. 39. 



Only found in the pack-ice and here — especially in August 

 1906 — the dominant species in some samples. In July— August 

 1908 not so common. 



Only the f. semispina was seen. 



Distrib. Northern oceanic species of wide distribution. 



18. Rhizosolenia obtusa Hensen, V. Ber. Komm. Unters. Deut- 

 schen Meere, 1887, p. 86, pi. 5, fig. 41 ; Gran, Nord. Plankton XIX, p. 56; 

 R. alata, var. triincata Gran, Norske Nordhavs Exp., Protophyta, 

 1897, p. 6, pi. 4, fig. 67. 



Only found in the pack-ice and in the same samples where 

 R. hebetata, f. semispina was present. Dominant in some samples from 

 August 1906, not common in 1908. 



Distrib. Northern oceanic species known from the colder parts of 

 the North Atlantic and the Norwegian Sea, etc. 



Eucampia Ehrbg., 1839. 



19. Eucampia groenlandica Cleve, Bib. K. Svenska Vet. Akad. 

 Handl., Bd. 12, afd. 3, No. 4, 1896, p. 10, pi. 2, fig. 10; Jørgensen, Ber- 

 gens Museum Skrifter, 1905, p. 99, pi. 6, fig. 8; Gran, Nord. Plankton, 

 XIX, 1905, p. 99, fig. 127. 



Single chains were found in four samples of July 1908 from 

 Danmarks Havn and the coastal water, not in the pack-ice. 



In some cases the chains were like Gran's f. atlantica (fig. 127 d), 



