2^^ DISCOVERY REPORTS 



which it is almost impossible to describe.^ Some of the large species possess charac- 

 teristic structures and rich colourings that make them easy to recognize with the naked 

 eye- E superba may be recognized by its densely plumose thoracic legs and strong red 

 colouring, E. triacantha by its brilliant red and orange and its three abdominal spines. But 

 the smaller species without such obvious structures or such conspicuous markings may be 

 as readily distinguished from one another by their general appearance when many have 



been seen and handled. 



The majority of the specimens that form the basis of a part of this report were 

 identified at sea the day after they were taken. They were examined under a dissecting 

 microscope and a large number of them were sexed and measured. The data so obtained 

 will, it is hoped, be used for the preparation of another paper on the life histories of the 



'^ Kght of the ten species described here are the only Euphausia found in the Antarctic 

 and sub-Antarctic Zones. Each of them, with the exception of E. triacantha, is normally 

 confined not only to one of the two zones but to a part of one zone. But most of them 

 may occur throughout the zone of which they normally occupy only a part, and some 

 may be found even outside the zone to which they are usually confined. The more 

 abnormal occurrences can mostly be explained by water movements that are local and 

 peculiar for reasons of place or time, as the many examples described later in this report 



' The normal and the possible range of latitudinal distribution of each of the species 

 is shown diagrammatically in Fig. 6. , • • u 



The figure shows that the usual number of Euphausia to be found at one point in the 

 sub-Antarctic is two, three or four. In the warmer sub-Antarctic E. shmlis, E. lucens 

 and E lorigirostris occur. A little farther south E. vallentini is added to the number. 

 Farther still E. lucens and E. similis cease to occur and E. triacantha appears. E 

 longirostris is sometimes absent from the coldest water leaving only E. vallentim and 



E. triacantha. , ^ . ^, , 



In the ice-free part of the Antarctic Zone there are usually only E. triacantha and 

 E frigida though in some large areas E. superba occurs too, widely distributed as far 

 north as the convergence. Along and among the ice itself only E. superba is ound 

 Farthest south of all is E. crystallorophias, a neritic species confined to the coast-line ot 



the Antarctic continent. 



The warmer sub-Antarctic species may be brought as far south as the Antarctic con- 

 vergence and E. frigida and E. superba may be carried a short way north of the con- 

 vergence' from the Antarctic. In this way it is possible that seven of the eight species 

 may occur in one place, immediately north of the Antarctic convergence, and taken in 

 one net This is indicated by the section AB in the figure. The largest number taken 

 at any of the 200 stations shown on the distribution charts in this report was five; that 

 number occurred at six stations all immediately north of the Antarctic convergence. 



1 I have not seen E. hanseni nor many specimens of E. crystallorophias in a fresh condition. 



