PELAGIC ANIMAL LIFE 625 



Three species of pteropoda [Peraclis divcrsa, Limacina 

 helicoides and Clio falcata) live below 500 metres, but accord- 

 ing to Bonnevie, the first of these seems to avoid the cold 

 bottom water, while the second species seems to prefer this 

 water and the third seems indifferent. All three forms are 

 dark -coloured, and their structure differs from that of the 

 surface forms, being of a more archaic type. 



All the large groups of squids include bathypelagic species, 

 of which the following may be mentioned : — 



CEgopsidge : Calliteuthis reversa, Mastigoteuthis flammea, M. grhnaldi and 



M. hjorti, Grivialditeuthis bonplandi, Toxeuma belone. 

 Myopsidas : larvje of Spirula. 

 Octopoda : Ekdonella pygmcBa^ Vampyroteuthis infernalis, Cirrothauma murrayi. 



Many peculiar species of fish were found at and beyond 750 

 metres, for instance : Malacosteus indicus and M. niger, 

 GastrostomiLS bairdii, Cyema atrum, Gonostoma grande, 

 Melainphaes mizolepis, Cetomimus storeri and a closely allied 

 new genus. Of eight species of Ceratiidae seven have been 

 taken only beyond 500 metres. Acei^atias inacrorhinus indicus 

 may also be mentioned. 



Proceeding to consider the horizontal or geographical dis- Horizontal 

 tribution of these forms, we commence with the most abundant 

 species of fish, Cyclothoiie signata and C. microdon. The chart 

 (Fig. 476) shows the localities where these species have been 

 taken previous to and during the " Michael Sars " Expedition, 

 and it is seen that the records are so numerous that these 

 fishes may be said to occur all over the area examined, wherever 

 a fishing appliance was lowered to a depth of 500 metres. 

 They are found everywhere, from the Wyville Thomson Ridge 

 in the north to beyond the Azores in the south, and from the 

 slopes of Africa and Europe to the slopes of America ; but the 

 distribution of the two species is not identical. Cyclothone 

 microdon has been captured by previous expeditions ^ on both 

 sides of Greenland, in Davis Straits, in Denmark Straits, and 

 also south of Iceland, whereas C. signata is unknown in these 

 localities ; and outside the Atlantic C. microdon occurs in the 

 Pacific, in the Indian Ocean, and in the Antarctic south 

 of lat. 50° S., whereas C. signata is much more restricted in 

 its southern distribution, having been taken at only one locality 

 to the south of lat. 40° S. 



The peculiar vertical and horizontal distribution of the two 



^ This information is derived from a chart in Brauer's paper on the deep-sea fishes of the 

 " Valdivia " Expedition. 



2 S 



distribution of 

 Cyclothone. 



