ZOOGEOGRAPHICAL REMARKS 99 



of bathypelagic Trachylina. It is very interesting that three of the species, Pandea rubra, Chromatonema 

 rubrum and Tiaranna rotunda, were taken in the antarctic region (see fig. 5, p. 26) in company with 

 several bathypelagic species of Trachymedusae. They were taken in the deep water below the antarctic 

 surface water at temperatures ranging between about 0° and i-y'^C. Hydrographical observations 

 are not available from all the localities where these species were collected, but from observations at 

 neighbouring stations the temperatures may approximately be stated as follows : 



Pandea rubra 



St. 151. North of South Georgia. Jan. 1927. 1025-127501. i-i-5°C. 

 St. 1131. East of South Georgia. Feb. 1933. 1000-800 m. i-6-i7°C. 

 St. 1989. South-east of South Georgia. Mar. 1937. 1500-120001. o-2-o-4°C. 



Tiaranna rotunda 



St. 1702. Off Wilkes Land. Mar. 1936. 2000-125001. o°C. 



St. 1723. Off Queen Mary Land. Mar. 1936. 800-50001. i-6-i7°C. 



Chromatonema rubrum 



St. 1719. Off Knox Land. Mar. 1936. 950-5501. o-3-o-5°C. 

 St. 1780. South-west of Bouvet Islaod. June 1936. 700-450 m. i-5°C. 

 St. 1871. East of Graham Land. Nov. 1936. 1450-1000 m. o-o-4°C. 

 St. 2006. Off Coats Land. Mar. 1937. 1750-140001.? 



The temperatures in the deep and intermediate layers in the warm seas, where these medusae also 

 occur, are not much higher, usually below 4° or 5° C, and from the North-Atlantic basin Tiaranna and 

 Chromatonema penetrate far up into the Davis Strait west of Greenland; they may therefore be desig- 

 nated as bathypelagic cold-water species. Apparently Annatiara affinis and Bythotiara murrayi do 

 not penetrate into the subantarctic or antarctic regions. They are not so strictly bathypelagic as the 

 other species mentioned above, but belong rather to the intermediate layers, about 200-400 m. or 

 so below the surface, where the water-temperatures are somewhat higher than in the deep-sea proper. 



Trachylina predominantly bathypelagic. Ptychogastria polaris occupies a separate position ; it is 

 therefore not included in Table 4. It is partly benthic, for it clings to the sea-bottom by means of 

 the suckers on its tentacles, but may occasionally swim upwards in the water. It has a bipolar 

 distribution, occurring in arctic and northern-boreal as well as in antarctic areas. It was collected 

 by the Discovery Investigations, at the bottom in two localities in the neighbourhood of the South 

 Shetland Islands, St. 177, depth 1080 m. and St. 1958, depth 830 m. We have no information of the 

 bottom-temperatures at these stations; they have presumably been about 0-5-1° C. 



The distribution of the two species at the bottom of Table 4, Crossota alba and Tetrorchis erythro- 

 gaster, is imperfectly known and needs no discussion here. 



Haliscera racovitzae and the three species of Arctapodema have a predominantly antarctic distribu- 

 tion, though A. amplum also occurs in the tropical Atlantic and in the Mediterranean; the others were 

 previously known only from antarctic seas, where they occur at intermediate depths, not m the deepest 

 layers. Haliscera racovitzae was taken at St. 355, east of South Georgia, in a haul 750-500 m., tem- 

 perature unknown, probably abouti-y^C, and was previously recorded from the Weddell Sea and near 

 the Antarctic Continent, about 70° S, 82° W. Arctapodema amplum was taken at St. WS 160, north of 

 South Georgia, 550-250 m., temperature 2-0-1 -9° C, and at St. WS 388, off the South Shetland Islands, 

 400-250 m., temperature - 1-1° to - i-3°C. Since this species occurs in the tropical Atlantic and in 



13-2 



