NOTES ON SPECIES 291 



Asteromphalus parvulus Karsten. 



A small species that might perhaps be better placed in Group I, for it may well be 

 oceanic as Hendey maintains. It is frequently found living in pack-ice, however, and 

 from its time distribution in the plankton fits in well with the neritic/ice-edge group. 

 I have included extremely minute individuals, common along the ice-edge, with this 

 species in the qualitative counts. Some day these may prove to be distinct. This form 

 and the undoubtedly oceanic A. hookerii have a much more southerly distribution than 

 other members of the genus. 



Biddulphia striata Karsten. 



A strongly neritic species, very rare along the ice-edge in oceanic regions. It is 

 present in enormous numbers in the rich mixed plankton of neritic areas during the 

 main increase and has twice been seen to form very dense local concentrations during 

 the sporadic secondary autumnal increase. The formation of resting spores, more 

 heavily silicified and with punctate valves, was observed during a double crossing of the 

 Scotia Arc near the South Orkney Islands at the end of March 1938, and at South 

 Georgia a week later. These were very irregular in shape, and I think it probable that 

 some of the forms described by Van Heurck, which Mangin united under the name 

 B. polymorpha but which Hendey (1937, p. 277) has shown should be referred to as 

 B. anthropomorpha Van Heurck, will eventually turn out to be nothing more than 

 resting spores, or ' winter phases ', of B. striata Karsten. 



Eucampia balaustium Castracane, Hendey, 1937, pp. 285-6 = £". balanstium and 

 MoeUeria ontarctica Castracane (1886, pp. 97-8) = £'. antarctica Mangin (1915); 

 Hardy (Hardy and Gunther, 1935); Hart, 1934. 

 A typical neritic/ice-edge species with the characteristic time distribution of the 

 group, but in neritic areas it persists in some quantity later in the season. Like the 

 others, it is very abundant round South Georgia, in the channels of the Palmer Archi- 

 pelago, and, still farther south, around the Balleney Islands. The winter {balaustium or 

 type) phase is rarely found in chains of more than four frustules, but when the summer 

 (moelleria) phase is propagating rapidly extremely long spiral chains are formed which 

 coil up like corkscrews. These soon break up in preserved samples. Intermediates 

 between the two distinct phases are common in short chains of varying lengths and 

 isolated pairs of frustules. 



Chaetoceros flexuosum Mangin. 



A strictly neritic species mainly confined to the more southerly ice-fringed coasts, 

 and encountered at the open ice-edge only late in the year, when it lies far south near 

 the Antarctic continent. 



Chaetoceros neglectum Karsten. 



A typical neritic/ice-edge species in its distribution both in time and space. This 

 form has probably been confused with the smallest phases of Ch. dichaeta in the past, 



