NOTES ON SPECIES 157 



Rare and sporadic in Antarctic surface water, chiefly in old water in comparatively 

 low latitudes. 



Actinocyclus corona, Karst. 



Karsten, 1905, p. 92, pi. ix, fig. 6. 



Observed in srriall numbers at one station only, near the South Sandwich Islands, also 

 at one of the inshore stations in East Cumberland Bay, South Georgia. 



Actinocyclus spp. 



Indeterminate species of this genus were encountered in small numbers at a very few 

 stations, all within the Antarctic Zone. 



Genus Hemidiscus, WaUich, i860 

 Hemidiscus (Euodia) cuneiformis, WaUich. 

 Gran, 1905, p. 45, fig. 51. 



This, the Euodia cuneiformis of Schiitt, 1896, was encountered at one station just 

 north of the Equator, in long. 30° W. 



Family THALASSIOSIRACEAE, Lebour, 1930 



Genus Thalassiosira, Cleve, 1873 



Thalassiosira antarctica. Comber. 



Cleve, 1900, p. 919; Karsten, 1905, p. 73, pi. ii, figs. 2, 3; Mangin, 1915, p. 77, figs. 56, 57. 



Mangin has already drawn attention to the fact that the name of this species was pre- 

 occupied by Cleve (1900), who described it from the manuscript with photograph sent 

 to him by Comber. Karsten described it as a new species — under the same name ! It was 

 very widely distributed in all types of Antarctic surface water, and particularly abundant 

 in the older mixed water, mainly of western Weddell Sea origin, to the south-west of 

 South Georgia in spring. The spring maximum was very clearly shown by this species 

 in all regions for which we have any seasonal data. It is a very variable form sometimes 

 occurring in vast masses of gelatinous colonies, as depicted by Mangin, which render 

 its numerical estimation impossible. 



Genus Coscinosira, Gran, 1900 



Coscinosira antarctica, Mangin. 

 Mangin, 1915, pp. 55-7, fig. 39. 



Observed at a few stations to the south-west of South Georgia in spring only. Very 

 difficult to distinguish from the last named when it occurs in bulk. 



Family SKELETONEMACEAE, Lebour, 1930 

 Genus Stephanopyxis, Ehrenberg, 1844 

 Stephanopyxis spp. 



Frequent round South Africa and to the east of Patagonia, referred to incidentally 

 on p. 25. 



