NOTES ON SPECIES 165 



north-east of the South Sandwich Islands, early in spring. The only other stations at 

 which Ch. radiculum was observed were in the old water of Bellingshausen Sea origin 

 in the western part of the Scotia Sea. There it occurred at one early spring station and 

 at three worked in late autumn. 



Chaetoceros schimperianus, Karst. 



Karsten, 1905, p. 117, pi. xv, fig. 2; Mangin, 1915, p. 48, figs. 30-2. 



Abundant on the spring survey round South Georgia, mainly to the south-west. 

 Fairly frequent, but in much smaller numbers, farther south in both the Weddell and 

 the Bellingshausen Seas. Rare in Bransfield Strait. 



Chaetoceros socialis, Lauder. 



Lebour, 1930, p. 166, fig. 128; Gran, 1905, p. 96, fig. 123. 

 Extremely sporadic in its occurrence, but usually dominant when present. The 

 colonies in rich samples are so closely intermingled that counting is impossible even 

 at great dilutions, and they frequently render the counting of the other species present 

 very difficuk. Dominant to the south-west of South Georgia during the spring survey, 

 in the eddy of Weddell Sea water round Joinville Island in December, in the far south 

 of the Weddell Sea, at two stations at the Palmer Archipelago and at one in the Bellings- 

 hausen Sea. 



Chaetoceros tortissimus. Gran. 

 Mangin, 1915, p. 49, fig. 33. 



Very local in its distribution, but one of the dominant forms in inshore waters to the 

 north-east of the Bellingshausen Sea and at the Palmer Archipelago. Abundant also in 

 the eddy of Weddell Sea water into the eastern end of Bransfield Strait. Present at only 

 one station off South Georgia, and one (far south) in the Weddell Sea. 



Family BIDDULPHIACEAE, Lebour, 1930 

 Genus Biddulphia, Gray, 1832 



Biddulphia (Triceratium) arcticum, Btw. 

 Karsten, 1905, p. 121, pi. xvi, fig, 7. 

 This littoral form was observed at one station to the north of Joinville Island, where 

 there was apparently a current flowing northward through Antarctic Sound. 



Biddulphia polymorpha, Mangin. 

 Mangin, 1915, pp. 23-7, figs. 2-5. 



Another littoral form, observed on only three occasions, twice in the vicinity of the 

 Biscoe Islands and once in East Cumberland Bay, South Georgia. 



Biddulphia striata, Karst. 



Karsten, 1905, p. 122, pi. xvii, figs. 2, 3; Mangin, 1915, p. 22, fig. i. 

 Widely distributed in all types of Antarctic surface water, but rare in the eastern 

 Weddell Sea. Abundant round South Georgia on the spring survey, mainly to the 



