484 DISCOVERY REPORTS 



been recorded from these islands except at an abyssal station. There are thus some 

 grounds for regarding the Cellularine Polyzoa of the islands of the South Indian Ocean 

 as sub-Antarctic rather than Antarctic. 



It has seemed best to count Tristan da Cunha as sub-Antarctic, for the purposes of 

 Table 3, although Deacon (1937, p. 59) shows that the subtropical convergence some- 

 times runs to the north and sometimes to the south of the island, which is thus not fully 

 sub-Antarctic. Of the five species from Tristan in this report, two, Caberea darwinii 

 and Cornucopina pectogemma, are real Antarctic-sub- Antarctic species; two, Scrupo- 

 cellaria ornithorhyncus and Aetea anguina, are found at various sub-Antarctic localities, 

 but also extend more or less widely north of the area; and one, Caberea rostrata, is 

 known from New Zealand. 



In the Antarctic area the Weddell and Victoria Quadrants are on opposite sides of 

 the Antarctic continent, and nearly half the species have only been found at one side or 

 the other. 



Table 3 A shows the distribution of the abyssal species known from the Antarctic 

 and sub-Antarctic areas (o in Table 3). The heavy lines A and B again represent the 

 subtropical and Antarctic convergences respectively. Species from both sides of the 

 Antarctic convergence have been recorded at localities north of the subtropical con- 

 vergence, but there are only two species, Himatitozoum sinuosum and Cornucopina 

 infundibulata, that are known from both the Antarctic and the sub-Antarctic areas. 



The three zones separated by the convergences have been subdivided geographically 

 so that the table comprises eight sections. Considering the nine species that have been 

 recorded from more than one of these sections, one notices, in the first place, that the 

 more northerly records of the sub- Antarctic South Indian Ocean species are from the 

 geographically adjacent Malay Archipelago, but that the species south of the Antarctic 

 convergence have been found in the Atlantic Ocean or the northern part of the Indian 

 Ocean, both of which are separated from the Antarctic localities by areas in which the 

 species have not been found. 



Deacon (1937, fig. 1) gives a diagram of the meridional circulation in the Atlantic 

 Ocean, and has found a very similar circulation throughout the Southern Ocean (1937, 

 pp. 3 etc. and figs. 5, 8). 



Comparing Table 3 A with Deacon's diagram it appears that two of the Atlantic 

 stations at which the Antarctic species were found, being below 4000 m. in the region 

 north of the subtropical convergence, may well have been under the influence of the 

 Antarctic bottom current and therefore comparable hydrologically to the Antarctic 

 abyssal stations. (The third station was in only 3477 m.) Similarly the South Indian 

 Ocean station with Malayan species was at 2938 m. in the region between the two con- 

 vergences and was probably in the warm deep layer (see Deacon, 1937, pp. 3, 81). The 

 Pacific station off Valparaiso is just south of the subtropical convergence in 3953 m., 

 and may also have been in the warm deep layer. Its species are known from Malayan 

 and South Indian localities, like the last group, and also from a relatively shallow station 

 off Brazil, for which I have no hydrological data. The only marked discrepancy is the 

 two Antarctic forms found off East Africa. 



