154 DISCOVERY REPORTS 



worked farther north. From the material at our disposal it has therefore not been 

 possible to do more than identify most of the species roughly and note the stations at 

 which they occurred. The analyses upon which this paper is based were all made before 

 the recent important paper of N. Peters (1932), on the Ceratia of the South Atlantic, 

 was published. Some of his findings will doubtless lead to a clearer conception of the 

 distribution of this group, notably his observations on their relation to the concentrations 

 of nutrient salts present in the sea water. 



In compiling the references, preference has been given where possible to works to 

 which plankton workers are likely to have access. In many cases where more than one 

 reference has been given, this has been done for the sake of the figures. Thus Mangin 

 has usually little to add to the earlier descriptions, but his simple line drawings are often 

 much more useful in working through large samples preserved in bulk, than other more 

 elaborate figures. It will be realized that the distributional notes are based on material 

 collected prior to 1932, and that further work may lead to considerable modifications. 



Class DIATO MALES 



Family MELOSIRACEAE, Schroder, 191 1 



Genus Melosira, Agardh, 1824 

 Melosira sol, Ehrb. 



Karsten, 1905, pp. 70-72, pi. i, figs. 3-9. 



A littoral Antarctic form observed in moderate numbers on one occasion at the South 

 Sandwich Islands, and elsewhere only occasionally in Bransfield Strait and off Adelaide 

 Island, close inshore. In Bransfield Strait it was present in the eddy of Weddell Sea 

 water round Joinville Island, having apparently drifted north with other littoral forms, 

 in the current through Antarctic Sound. 



Melosira sphaerica, Karst. 



Karsten, 1905, p. 70, pi. i, fig. 2. 

 Rarely and in small numbers in old Antarctic surface water. 



Genus Hyalodiscus, Ehrenberg, 1845 

 Hyalodiscus chromatoaster, Karst. 

 Karsten, 1905, p. 74, pi. ii, figs. 4, 5. 

 Observed at one station only during the spring survey round South Georgia. 



Hyalodiscus kerguelensis, Karst. 

 Karsten, 1905, p. 74, pi. ii, figs. 6, 7. 



At two stations on the spring survey round South Georgia, abundant at St. WS 531 

 on the Burdwood Bank, just to the north of the Antarctic convergence; rare and 

 sporadic farther south. 



