OF THE ' SOUTHERTf CROSS ' EXPEDITION. 39 



I have no intention of putting forward any theory to account 

 for the similarity of the two Polar Amphipodal faunas : our 

 knowledge of this class of animals and the material at our 

 disposal are quite insufficient for generalization. But it is worth 

 while to consider the distribution of the small genus Orclio- 

 menopsis, established by Gr. 0. Sars in his beautiful work on the 

 Amphipoda of Norway in 1805. So far as I know, the following 

 are all the species yet obtained : — 



0. ohtiisa^ Gr. O. Sars. The tyjie, Trondhjemsfiord, lOOfath. 



O. {Orcliomene) miisculosus (Stebbing). ' Challenger.' S. of 

 Japan, N. lat. 2G°, E. long. 138^ 2425 fath. Temperature 35°-6.* 



0. ahyssorum (Steb.). ' Challenger.' E. of Buenos Ayres, 

 S. lat. 36°, W. long. 51°. 1900 fath. Temp. 33°. 



Do. G. Murray in the ' Oceana,' Nov. 1898 [Ann. & 

 Mag. Nat. Hist. ser. 7, xii. (1903) p. 232, iued.]. N. lat. 52° 18', 

 A¥. long. 15° 53', 1610 and 1410 faths. 



Do. Chevreux (Camp. Sci. de I'Hirondelle, p. 23). N. lat. 

 48°, W. long. 51°. 1103 fatli. [Chevreux has also described 

 (Bull. Soe. Zool. France, xxviii. (1903) pp. 93-96) two new 

 species from the North Atlantic] 



O. nodimanus, A. 0. Walker. Cape Adare. 26 fath. Temp. 

 28°-8. 



0. Bossi, A. 0. Walker. Franklin Island. Surface; lat. 78° 35'. 



If to these we add, as Gr. 0. Sars is inclined to, Orcliomene 

 cavimanus, Stebbing, from Kerguelen Island, we shall probably 

 have all the known species. It wall be seen that Orchomenopsis 

 is distributed over a very large part of the world's area, and that in 

 every case it has been taken in water at a low temperature. In 

 fact this, and not light, appears to be essential to the existence 

 of its species. 



Another deep-sea form which has not yet been found in 

 Antarctic waters, but which, I confidently expect, will be, is 

 Cyphocaris anonyx from the Greenland coast. In the ' Challenger ' 

 Heport, Mr. Stebbing describes a species, Cyphocaris mtcronyx, 

 from near Tristan da Cunha, taken in 1425 fath., temp. 37°, which 

 I believe he now considers identical with Liitken's species. And 

 in Mr. G. Murray's ' Oceana' gatherings the same species occurs 

 at depths of 510, 1300, and 1670 faths. These facts appear to 

 support the theory of a connection between the Poles by the 

 cold abyssal stratum of the Ocean. 



* Bottom temperature is always to be understood. 



