104 DISCOVERY REPORTS 



them have a circumglobal distribution in the warm and temperate zones, where they generally occur 

 in company with the five species mentioned above. Rhopalonema funerarium was taken some distance 

 north of South Georgia, 50^ 18' S, in the intermediate layers (340-150 m., temperature 2-5-i-5° C). 

 It is not strictly bathypelagic, being sometimes taken at less than 200 or 300 m. below the surface, 

 but usually deeper down (e.g. at St. 2064 in a haul 1600-1050 m.). In the waters west of Africa it 

 was taken at temperatures between about 4° and 9° C. Halitrephes maasi, which mainly belongs to 

 the southern hemisphere, may likewise be taken nearer the surface (e.g. at St. 893, south of Australia, 

 in iio-o m.); but as a rule it occurs at considerable depths. The lowest temperature at which it was 

 found by the Discovery Investigations was about 4° C, at St. WS 127, south of Gough Island, in 

 1000-650 m. Colohotiema sericeum was taken in deep water in numerous localities, partly west of the 

 tropical part of Africa, partly in the Atlantic and Indian Oceans, west and east of South Africa, at 

 temperatures from about 3° C. upwards. Aeginura grimaldii was only found in the tropical regions 

 west and east of Africa. With the exception of Halitrephes maasi, these species occur in the northern 

 Atlantic at temperatures similar to those at which they were found near their southern limits of 

 distribution. Though in their principal areas of distribution, horizontal as well as vertical, these 

 species concur with the other bathypelagic Trachylina, they evidently require a slightly higher 

 temperature than species which are able to penetrate into the deep water of the antarctic region. 



SUMMARY OF THE ZOOGEOGRAPHICAL RESULTS 



The Discovery Investigations have greatly augmented our knowledge of the geographical distribution 

 of the Hydromedusae ; in all the areas examined some species were found which had not been observed 

 there before. The numbers are seen in the tables, but it should be noted that the number of species 

 taken in each region is not an index of the variety of the medusan fauna, for the intensitv of sampling 

 was very uneven in the different regions. Nevertheless, the figures tell us something about the results 

 obtained. 



According to the maps of distribution produced by Thiel (1936), some species of Trachylina might 

 previously have been taken in areas whence in the present paper they are designated as new, but, as 

 already mentioned, Thiel has in several cases united two or more species which makes his maps 

 unreliable. 



A number of species are endemic in the antarctic region, most of them neritic species of Leptolina, 

 and we can now state that their distribution is circumpolar (Table 2). Two of them, together with two 

 species previously known only from the Falkland Islands, are found to inhabit the coastal waters of 

 South Africa. Among the bathypelagic Trachylina three species presumably belong to the antarctic 

 seas, but two of them were taken in deep water within a restricted area farther north, 32° S, in the 

 Indian Ocean (Table 4). Altogether ten species were found as new to the antarctic region, four of 

 them are new species, and three of them are bathypelagic Anthomedusae which are widely distributed 

 in the Atlantic Ocean from north to south (Table 4). Most of the species new to antarctic waters were 

 found in the Atlantic sector, which was much more thoroughly investigated than the other sectors. 



Our previous knowledge of the fauna of Hydromedusae in the waters off the east coast of South 

 America was deficient. Twenty-eight species were collected in the antiboreal part of the south-western 

 Atlantic, fifteen of them new to the region. The neritic and epipelagic fauna of Hydromedusae in this 

 region is a mixture of species of very different origins ; some few of them may be designated as true 

 warm-water species, but most of them occur both in tropical and boreal waters (Tables 2 and 3). 

 There are, however, also a number of neritic Leptolina which are characteristic of this region, though 

 some of them have extended their distribution into the South African region. It is of particular 



