gg DISCOVERY REPORTS 



and has now been taken in South African waters. The nineteen other Discovery species all occur in 

 the East-Atlantic-tropical region, and fifteen of these are also found in the Mediterranean-Atlantic 

 region and seventeen in the West-Atlantic-tropical region. Only seven species are distributed farther 

 north into boreal waters in the North Atlantic, all of them as more or less stray visitors from the 

 south; among them Solmaris corona which occurs in the eastern Atlantic, from South Africa to 



Norway. 



Of particular interest is the southward distribution of the eighteen species which are more or less 

 generally distributed in the warm parts of the Atlantic, most of them being also known to occur in the 

 Indian and Pacific Oceans. With two exceptions {Pegantha triloba and Pegantha rubiginosa) they are 

 all found in the South African region. In the western Atlantic eight of the species occur in the 

 antiboreal region; as stated on page 96 this region receives a considerable admixture of neritic 

 medusae from the tropical region. On the other hand, the Antarctic Convergence seems to establish 

 as efi'ective a barrier to the southward distribution of the holopelagic, epipelagic TrachyUna as in 

 the case of the neritic Leptolina. According to some diagrams given by Dilwyn John (1936, fig. 6, 

 p. 203 and fig. 29, p. 246) the Antarctic Convergence seems to establish an equally sharp barrier to 

 the distribution of the southern species of Euphausia. None of the epipelagic TrachyUna are charac- 

 teristic of the antarctic region, and only two of the species belonging to warmer seas have been found 

 in antarctic waters, Solmiindella bitentaculata which is circumpolar, and Pegantha martagon which 

 was taken in the Pacific as well as in the Atlantic sector of the antarctic region. These two species must 

 accordingly be very eurythermal, whereas none of the other species are able to cross the Antarctic 

 Convergence. 



Oceanic species of Leptolina and Trachylina 



PREDOMINANTLY BATHYPELAGIC (Table 4) 



Most species of bathypelagic medusae have a more or less circumglobal distribution, and several of 

 them also have an extensive distribution from north to south. Submarine barriers may prevent them 

 from penetrating into enclosed deep-sea areas, otherwise they are independent of the coasts. A survey 

 of their geographical distribution may therefore be given by means of comparatively few, wide regions. 

 It is, however, insufficient merely to distinguish between warm- water and cold-water regions, so I have 

 subdivided them in order to give a clearer impression of the distribution of the species, with special 

 regard to the results obtained by the Discovery Investigations. 



With the exception of the semibenthic Ptychogastria polaris, none of the bathypelagic species collected 

 by the Discovery Investigations occurs in arctic deep-sea areas. It therefore seems best to exclude the 

 Arctic region and to divide the great oceans into boreal, tropical, and antiboreal belts. The Antarctic 

 region with its three sectors must, however, be kept separate. The interesting series of stations oflF 

 the east coast of Africa also calls for a separate treatment of this region, as do the waters around 

 South Africa, because the latter form a transitional area between the Atlantic and the Indian Oceans, 

 and because extensive collections were made there. 



Leptolina predominantly bathypelagic. Besides the new species Euphysora gigantea, which was 

 taken in deep water in the Atlantic sector of the antarctic region and in the antiboreal part of the 

 south-western Atlantic, six species belonging to this group were collected, all of them Anthomedusae. 

 Calycopsis bigelowi was previously known from the East-African-tropical region only ; now it has been 

 taken in deep water west of the Cape of Good Hope. The five other species are widely distributed in 

 the deep parts of the Atlantic Ocean, in tropical as well as boreal regions. With the exception of 

 Pandea rubra, which occurs in the northern Pacific, none of these species are recorded with certainty 

 from Indo-Pacific waters; this is remarkable, considering the wide distribution of almost all species 



