SCYPHOMEDUSAE 361 



Geographical distribution (Fig. 2). Our knowledge of the distribution of the 

 genus Periphylla in the Atlantic Ocean has been augmented rather extensively by the 

 Michael Sars and the Discovery Expeditions. The former explored the Atlantic from 

 Baffin Bay to Cape Verde, the latter from Cape Verde to the Antarctic; thus both 

 expeditions together explored the whole Atlantic from the far north to the far south. 

 A gap still exists in the Western Atlantic between 30° N and 30° S, because both ex- 

 peditions worked in these regions mainly in the eastern part along the African coast ; 

 but this gap has at least partially been filled recently by Bigelow's Arcturus explorations 

 (1928). The tropical waters above the South Atlantic ridge are still poorly explored. 



Periphylla has been found by the ' Discovery ' on its entire course from the tropics 

 to the Antarctic Continent (Fig. 2 represents mainly the hauls between 30 and 70° S). 

 It is very abundant in the neighbourhood of the West African coast (Cape Verde, 

 Gulf of Guinea, South Africa), and has been collected quite often in a region between 

 30 and 60° S. A few specimens only have been taken in Antarctic waters (St. 590, 

 Bellingshausen Sea, and St. 592, South Shetlands). 



This agrees with the records of previous expeditions, which found Periphylla in the 

 Pacific from the Sandwich Islands and California to Cape Adare and in the Indian 

 Ocean from Aden and east of Sumatra to the border of the Antarctic Continent. 



Our three forms, however, are not equally distributed over the Atlantic. An inspection 

 of Broch's chart (fig. 4) and mine reveals the fact that the largest specimens of the 

 hyacinthina and regina types have never been taken in the neighbourhood of the coast. 

 Our small dodecabostrycha, however, have with a few exceptions only been found in the 

 neighbourhood of the coast. As to hyacinthina and dodecabostrycha both charts are not 

 directly comparable, because the " hyacinthitia" of Broch contains our small dodecabo- 

 strycha and pointed hyacifithina and our regina embraces all large dodecabostrycha and 

 regina. According to the present hauls the forms hyacinthina and regina are pelagic 

 forms of the open sea (" Hochsee formen ") and are caught as a rule far from the coast. 

 This agrees with the results of the Michael Sars Expedition (chart 4) with the exception 

 of the one specimen from the Straits of Gibraltar. It seems rather strange that between 

 30° N and 30° S no regina is known in the Atlantic Ocean. This fact can, I believe, 

 only be explained by the circumstance that in this region the open sea is practically un- 

 explored. In the other oceans forma regina has been found in the tropics (Maas, 1897 ; 

 Bigelow, 1909, 1928) near the Galapagos and in the Gulf of Aden. All other occurrences 

 are from sub-Antarctic waters. How Broch can presume (p. 9) that P. regina has only 

 been found in the tropical and sub-tropical parts of the ocean I cannot understand, but 

 it seems very probable that later expeditions will find it in these regions. 



Another fact of interest is that small dodecabostrycha do not occur in deep-sea hauls 

 except in the neighbourhood of the Continental slope : for instance the Valdivia hauls 

 from Sts. 55, 746, 85, etc. (see Vanhoeffen, 1903, p. 23), and the Discovery Sts. 87, 

 256, 590. This makes it probable that the small stages of Periphylla have their origin on 

 the continental slope or near the coast (for instance, in the vicinity of South Georgia) and 

 that they are driven into the open sea and sink slozvly to greater depths. 



