CRUSTACEA MALACOSTRACA. III. 



in the cold deep-sea area, while 2 species have besides been taken in lesser depths. As to the limit- 

 ation of the warm deep-sea area, I proposed in 1913 that the stations with a depth between 300 and 

 600 fathoms and the temperature not below 3, and all stations with depths from 600 to 1870 fathoms 

 and the temperature above zero, might be considered as belonging to the warm area. About 56 of the 

 species (a few merely pelagical species not included) have been taken exclusively in this warm deep- 

 sea area by our Danish expeditions, but of these 8 species are also known from some lesser depths in 

 the Norwegian Fjords or Skager Rak. But a small number of species: Acanthaspidea typhlops G. O. 

 Sars, Munna acanthi/era n. sp., Haplomesus quadrispinosus G. O. Sars and H. angustus n. sp., Ilyarachna 

 hirticeps G. O. Sars, Eurycope inermis n. sp., Eur. brcvirostris n. sp., E. producta G. O. Sars, Munnopsis 

 typica M. Sars, Pleuroprion hystrix G. O. Sars, Astacilla granulata G. O. Sars and Calathura brachiata 

 Stimps. have been taken both in the real cold deep-sea area and at rather deep or very deep stations 

 in the warm area; three of these species, viz. Eurycope producta, Munnopsis typica and Calathura 

 brachiata, have besides been taken in depths of less than 100 fathoms either near Iceland, Norway, 

 East Greenland or in the Kara Sea, while a fourth species, Ilyarachna hirticeps, has been taken at 100 

 fathoms in Davis Strait and in 10 fathoms at Spitzbergen. Eurycope inermis has been taken seven 

 times in the warm area between 362 and 806 fathoms, and nine times in the cold area, in 293 to 1010 

 fathoms; Eur. brcvirostris has been taken twice in the cold area and once in the typical warm area. 

 As to the species mentioned of the genera Ilyarachna, Eurycope and Munnopsis, the hypothesis that 

 the animals sometimes live pelagically could at least to some degree explain their occurrence, and that 

 the animals have three pairs of natatory legs, and can swim, is well known, but unfortunately no 

 observation has ever been recorded that any species has been taken pelagically, and the three most 

 common and widely distributed species, Ilyarachna hirticeps, Eurycope inermis and especially Munnopsis 

 typica, are so large, that they could scarcely escape or be overlooked. Munna acanthi/era has been 

 captured nine times in the warm, and three times in the cold, area, and these stations are very far 

 from the limits between the areas; Haplomesus quadrispinosus was taken by the "Ingolf" six times in 

 the cold area in depths from 371 to 1309 fathoms, and three times at some of the deepest stations, 

 1199 to 1870 fathoms, in the warm area, and as to these two species even the possibility of swimming 

 must be excluded. Pleuroprion hystrix G. O. Sars is known from stations decidedly belonging to both 

 areas, but all the stations are not very far from the limits between the areas; as to several of the 

 localities the same is the case with Astacilla granulata. 



In the report on the Tanaidacea I pointed out similar facts, viz. that i species of Apseudidae 

 and 7 species of Tanaidae had been taken in both areas; the females of two of these species have no 

 pleopods. In his Conspectus (1913), K. Stepheusen attempted to give an explanation of this inter- 

 esting distribution. He pronounced the submarine ridge between the Shetlands, the Faeroes, south- 

 eastern Iceland, and between North-west Iceland and East Greenland to constitute an "absolute line of 

 separation between two deep-sea faunas", so that no deep-sea form living in the warm area can be 

 found in the cold area, and vice-versa; the only exception being some few Echinodennata. Stephensen 

 therefore assumed that the Tanaidacea in question had been taken pelagically when they had been 

 secured in the area, where they normally did not live. In order to support this hypothesis he put 

 together the few records in the literature showing that animals of that order had been taken pelagi- 



