24 



DISCOVERY REPORTS 



The distribution of this particular form has been considered at length, partly because 

 Mangin's perfectly sound observations are liable to misinterpretation in the light of his 

 text, and partly because the occurrence of the species in large numbers may be of 

 assistance in the interpretation of future work, its maximum being reached near the 

 boundary between sub-Antarctic and sub-tropical surface waters. Its distribution in 

 the material examined for this paper is shown in Table 4, which illustrates the points 

 raised above. 



Table 4 



Returning to a more general consideration of the phytoplankton of the sub-Antarctic 

 surface water, there is no doubt that it is moderately rich at times, as described later 

 (p. 73). Despite its comparative poverty on this occasion, the total number of organ- 

 isms, very much smaller than in Antarctic surface water, was still higher than those 

 found farther north in sub-tropical and tropical surface waters. Thus the relative 

 abundance in the major types of surface water is quite fairly represented in Table 2. 

 This table also shows very clearly the gradual increase in the proportion of dinoflagellates 

 as one proceeds northwards. 



The following is a list of all the species found at the stations worked in sub-Antarctic 

 surface water in 30° W. Those printed in heavy type were exclusively confined to the 

 sub-Antarctic Zone ; of the others, all the diatom species were found also in the Antarctic 

 surface water, to which they properly belong. The cosmopolitan species Rhizosolenia 

 alata, R. styliformis and Cerathim fusus were also found in sub-tropical surface water. 



Coscinodiscus sp. 

 Dactyliosolen antcurticiis, Castr. 

 Corethron valdiviae, Karst. 

 Rhizosolenia alata f . gracillima 

 R. curva, Karst. 

 R. styliformis, Btw. 

 /?. torpedo, Karst. 

 Chaetoceros atlanticiis, Cleve 

 Ch. criophilum, Castr. 



Chaetoceros ? concavicornis, Mangin 



Nitzscliia scriata, Cleve 



Nitzschia sp. 



Goniaulax polygratntna, Stein 



Peridiniutn elegans, Karst. 



Peridiniuni spp. 



Ceratiiim fusus, Ehrb. 



C. tripos f. truncata, Lohm. 



