ßjg к. Stephensen. 



The whole of this group seem to be species which come from 

 the Pacific, migrating from there eastwards round the north of 

 America. As they are boreal on the whole and most do not occur 

 at arctic America, the migration cannot have taken place under the 

 present climatic conditions, but probably during an earlier, post- 

 glacial period, when Greenland had a warmer climate than now^ as 

 shown by Ad. S. Jensen (On the Mollusa of East Greenland, I. Lamelli- 

 branchiata; On the fossil quaternary Mollusc-Fauna of Greenland; 

 Meddel, om Grønland, vol. 29, 1909, pp. 289—305. — Ad. S. Jensen 

 and Poul Harder: "Postglacial changes of climate in arctic regions 

 as revealed by investigations on marine deposits"; Postglaciale Klim- 

 averanderungen (Geologorum conventus), Stockholm 1910, p. 399). 

 It is interesting, that Dr. Th. Mortensen has shown the same thing 



in regard to certain Echinoderms (Echinoderms — Danmark 



Exped., Meddel, om Grønland, vol. 45, 1910, pp. 298—300). Chionoecetes 

 opilio, Spirontocaris Fabricii and Sp. macilenta have not come further 

 than to W. Greenland, Neciocrangon lar and Spirontocaris groenlandica 

 have also reached E.Greenland; the remainder have come much 

 further. 



The Atlantic deep-water fauna (including the plankton) seems 

 for a great part to be cosmopolitan (except naturally in the cold 

 polar basin). The Danish "Ingolf Expedition first showed the differ- 

 ence in the deep-water fauna of the Atlantic and Polar Sea (H. Jun- 

 gersen, "Fra "Ingolf" Expeditionen", Geografisk Tidsskrift, vol. 14, 1898, 

 p. 36). It will have been noticed in the lists above, how many of 

 the Greenland deep-water species have been found in the Pacific or 

 even in the Indian Ocean, 



Our knowledge of the Greenland plankton has been obtained 

 mainly, as already indicated, from the Danish "Tjalfe" Expedition 

 to W. Greenland under the direction of Ad. S. Jensen in 1908—09. 

 This Expedition, which was sent to Greenland to study the possib- 

 ilities of a profitable fishery, brought home a very large material, 

 also of Crustacea. A paper on the Malacostraca of the Expedition 

 will very soon appear (in Vid. Medd. fra Naturh. Foren. Kbhvn., 

 vol. 64, 1912), and it will be shown therein, that many of the plank- 

 ton forms, which were known earlier from the Atlantic between the 

 Azores and S. W. Ireland (see especially Bull. Mus. Océanogr. Monaco; 

 Result, des camp. sc. — — — Albert I, Monaco; Fisheries, Ireland, 

 Sei. Invest.) have also now been found right up at the ridge in the 

 Davis Strait; this material, however, has also been used in the pre- 

 sent work. 



