ZOOGEOGRAPHICAL REMARKS 97 



the Other hand yields important results. Among the eleven neritic species taken there by the Investiga- 

 tions, two were previously known only from the tropical Indian and Pacific Oceans: Heterotiara fni?ior 

 has now been taken off the south-east coast of Africa, and Zygocanna vagans west of the Cape of Good 

 Hope. Neoturris pileata, regarded as a North Atlantic species, has been found considerably farther 

 south than before off the west coast of Africa. All the other species found in the South African region 

 also occur in the West-Atlantic-antiboreal region or in the Antarctic and three of them are widely 

 distributed in the Atlantic Ocean. One of these, Phialidiuni simplex, has a scattered distribution and 

 is known from North-East Australia, Brazil and the Falkland Islands. On the whole, the South 

 African neritic Leptolina evidently do not constitute a local fauna but are a mixture of species, widely 

 distributed and of different origins. 



However, in this region the most interesting finds are undoubtedly those of Sarsia gracilis and 

 Halithohis intermedins, previously known only from the Falkland Islands, and those of the two 

 antarctic circumpolar species, Mitrocomella frigida and Cosmetirella davisi, the last also occurring in 

 subantarctic waters near the Falkland Islands. All these medusae are so small that presumably their 

 pelagic life is of short duration and they have little chance of being carried long distances by the 

 currents. The nearest shallow-water area is the plateau of Bouvet Island, which is about 1300 miles 

 away from South Africa. We must presume, therefore, that there is an indigenous, local population 

 of these species in South African coastal waters. 



In the neighbourhood of South Georgia, Cosmetirella davisi was abundant in the surface water at 

 temperatures varying between about 0-5^ C. and 3° C. ; in subantarctic waters it lives at temperatures 

 of about 5-6° C., sometimes perhaps as high as (f C. (e.g. St. WS 832, near Patagonia). At St. 102, 

 a short distance south of the Cape of Good Hope, it was taken in October 1926 in about 54 m. below 

 the surface, where the temperature was about 14° C. Sarcia gracilis was taken at St. 91, in False 

 Bay, near Capetown, in September 1936, at 35 m. and in temperatures of about i3'5° C. Halithohis 

 intermedins was found in two South African localities, St. 1374 (May 1934) near the south-east coast, 

 and St. 100 (October 1926) west of Capetown, and Mitrocomella frigida occurred at St. 256, some- 

 what farther west of the Cape of Good Hope, in June 1927. Unfortunately we do not know the exact 

 depth of these finds, nor the temperatures, but the medusae were undoubtedly taken in the upper 

 layers in fairly warm water. The hydrographical conditions round the South African coasts are very 

 complicated, and the occurrence of these southern species must presumably be explained as being 

 due to the cooling influence of the Benguela Current. 



Very few neritic species of Leptolina were collected in the East- African-tropical region, where 

 Octophiahiciiim aphrodite occurred, or in the Peru-Chilensic region where Aequorea coerulescens and 

 A. macrodactyla were taken. The occurrence of these three species in these regions presents nothing 

 of particular interest. 



Oceanic species of Leptolina and Trachylina 



PREDOMINANTLY EPIPELAGIC (Table 3) 



Of the oceanic Leptolina, predominantly epipelagic, four species were taken by the Discovery Inves- 

 tigations. All of them occur in the warm parts of the oceans, although Phialopsis diegensis is also 

 recorded from boreal waters. Bougainvillia platygaster and Euphysora furcata have so far only been 

 taken in the Atlantic and in the westernmost parts of the Indian Ocean. None of the four species are 

 found in antiboreal or antarctic seas. 



Of the oceanic Trachylina, predominantly epipelagic, twenty species were collected by the Discovery 

 Investigations, the majority of them being widely distributed in all the great oceans, mainly in the 

 tropical regions. One species, Ciinina globosa, was previously known only from the tropical East Pacific 

 13 ""'^ 



