DISTRIBUTION OF ANTARCTIC MACROPLANKTON 103 



In the coastal region of the South Orkneys and South Shetlands and in the Bellings- 

 hausen Sea it occurs sometimes in small numbers. It was not taken at stations in the 

 eastern Weddell Sea. In general it occurs in varying quantities but appears never to 

 form shoals. 



Euphausia crystallorophias. Like Antarclomysis this must be regarded as a neritic 

 species. It is found, however, only in the colder regions such as the Bransfield Strait 

 and the coastal waters of the eastern part of the Bellingshausen Sea. 



Euphausia triacantha. This species occurs in a more strictly limited zone than perhaps 

 any other. To the north it is found only a little way beyond the convergence and to the 

 south it is bounded normally by a line from the South Shetlands running north- 

 eastwards and passing a little to the south of South Georgia. It is thus a typically 

 warm-water species, but it is curious that it does not normally extend far into the 

 sub-Antarctic Zone as do most of the other species typical of the warmer parts of the 

 Antarctic. This fact may perhaps be in some way due to the depth at which it lives. 

 There is no reason for supposing that it forms shoals or local concentrations. 



Euphausia vallentini. This is reallv a sub-Antarctic species, but it sometimes strays 

 south of the convergence and has even been taken off South Georgia on one or two 

 occasions. Zimmer (1914) records a specimen from 58 29' S, 89 58' E, a very high 

 latitude for this species. 



Thysanoessa spp. There have been very few samples which did not contain repre- 

 sentatives of this genus. It seems always to be scarce in the Bellingshausen and eastern 

 Weddell Seas, but in the warmer parts of the outer Antarctic, in the outflowing Weddell 

 water and around South Georgia it is often taken in thousands. As a genus it is very 

 variable and patchy, and this characteristic is probably shared by T. macrura and 

 T. vicina. 



Cleodora sulcata. Distributed everywhere from the Bellingshausen Sea to the coldest 

 regions. In most places it is taken normally in ones and twos, but it is more plentiful 

 in the Weddell Sea water in the neighbourhood of the South Sandwich Islands. Here 

 there have been single hauls containing several hundred specimens, and such hauls 

 might be regarded as indicating at least a local concentration. It is distinctly a cold- 

 water species. 



Limacina helicina. This is pre-eminently a cold-water species, but at times it is found 

 as far north as the convergence. There are no very definite limits to its distribution, but 

 its occurrence seems to vary according to the time of year. There is no indication that it 

 forms shoals or dense local aggregations such as we find in the case of L. balea. 



Limacina balea. The distribution of this species is quite different from that of 

 L. helicina. The two are sometimes found together, but L. balea is more of a warm- 

 water species and seems to reach its greatest development near the convergence. No 

 specimens have been taken in the Bellingshausen Sea or in the eastern Weddell Sea, 

 though it occurs in the outflowing Weddell water. In the warmer parts of the Antarctic 

 water it has occasionally been found in enormous swarms. Some big catches have also 

 been taken off South Georgia and between South Georgia and Bouvet Island. 



