MEDUSA. I. 



2 9 



Channel (under the name of Laodice calcarata] in the International Plankton Catalogues (Catalogue, 

 1906, 1909, and 1916). We have to be very cautious, it is true, in employing these catalogues, as the 

 identifications of the species have, as a rule, not been made by specialists; in the present case, how- 

 ever, I believe the identification to be correct. In one particular instant I have been able to verify the 

 identification directly, some specimens being present in the type collection of the plankton laboratory 

 in Copenhagen. During the years from 1903 to 1908 the species has been taken in the Channel 

 almost every year in the month of August, and sometimes also in May; only once it was found in 

 November (1905). It was found in the Bristol Channel in August 1905, 1906, and 1907, and in May 

 1908. It has also on one occasion been found in the North Sea off the coast of Belgium, viz. in Au- 

 gust 1905. 



As far as I am aware, Laodicea undulata has never been recorded from the east coast of Great 

 Britain south of St. Andrews. 



Neither has it been mentioned from Heligoland. 



I have worked through a very considerable material of plankton from the Horns Rev light- 

 vessel off the southern part of the west coast of Jutland, but I have only found one single, small 

 specimen of this species. 



It seems also to be scarce in the Skagerrak, in so far as it has only been observed twice in 

 that sea; it does' not penetrate into the Kattegat. 



I have never seen this species recorded from the west coast of Norway, and it seems, on the 

 whole, to be altogether lacking in the Norwegian Sea 1 . 



Nor is it known to occur off the Atlantic coasts of Europe south of the British Channel. 



If we compare the records of the literature with the data derived from the material examined 

 by me, we will gain the following general picture of the horizontal distribution of Laodicea undulata 

 in the North-East Atlantic area: The species occurs off the southern coasts of Iceland, is numerous 

 around the Rockall plateau and Scotland ; it is also found, though apparently in smaller quantities, off 

 the western coasts of Ireland and England, in the Channel, and in the south-western part of the North 

 Sea. Finally it may be found, occasionally, off the western and northern coasts of Jutland. 



All records agree, that this species does not occur in any great distance from the coasts, that 

 the distance from the shore, accordingly, sets a limit to the horizontal distribution. On the other hand, 

 the actual depth is without importance with regard to the occurrence. Some of the specimens 

 here dealt with have been taken in shallow water near the coasts or above the Rockall Bank, 

 others have been found above very deep water, as for instance on the "Thor" stat. 180(04), where the 

 depth was 2160 in, and several specimens have been found in the Rockall Channel, the Faeroe-Shet- 

 land Channel, and the Norwegian Channel. 



With regard to the vertical distribution we will find, that the species may occur in very diffe- 

 rent depths below the surface, it having been found in all strata between the surface and about 800 m 

 below the surface. The results of the cruise of the "Armauer Hansen" in 1913 are particularly instruc- 

 tive with regard to the occurrence of this species. Laodicea undulata was lacking on all of the 



') Hartlaub (1900, p. 172) mentions numerous specimens "der schonen, scheinbar magenloseu Laodice crucfata", found 

 during the expedition of the "Olga' 1 at Tromso (northern Norway) on June 28th 1898. If the identification be correct, we have 

 here an isolated find of high interest. 



