1 1 :; 



as the type of the genus, and is easily recognizable from most other Calanoids 

 by its very slender and elongated form. 



Occurrence. I have met with this form along the whole Norwegian coast, 

 from the Christiania Fjord to Vadso. hut as a rule only in greater depths, below 

 100 fathoms. This form often occurs in great abundance, especially in the 

 deep fjords; and it was also found rather frequently in some of the samples of 

 plankton taken from deep water in the open sea during the cruise of the "Mi- 

 chael Sars". In the living state it is so exceedingly pellucid, that in spite of its 

 comparatively large size, it is not easy to detect. It moves in the usual manner, 

 now proceeding at quite an even rate by rapid vibrations of the posterior antennae, 

 now jumping along abruptly by powerful strokes of the natatory legs and urosome. 

 When disturbed, it sends out from its body a bright flash of a bluish colour. This 

 flash is so intense, that even by full day-light it can easily be seen. 



Distribution. Faroe Channel (Norman), Baffin's Bay (Hansen), Spitsbergen 

 (Tjilljeborg), the Kara Sea (Hansen), Polar basin crossed by Nansen (the present 

 author), Atlantic Ocean from lat. 56 to 76 N. (Giesbrecht). 



49. Metridia lueens, Boeck. 



(PI. LXXVII). 



Metridia lucens, Boeck. Oversigt over de ved Norges Kyster forekomne Copepoder. 

 Chr. Vid. Selsk. Forh. 1864, p. 238. 



Syn: Metridia armata, Brady (not Boeck). 

 Paracalanus hibernicus, Brady & Roberts. 

 Metridia hibernica, Giesbrecht. 



Specific Characters. Female. Body somewhat less slender than in the 

 preceding species. Cephalosome about the length of the metasome. and remarkably 

 vaulted above in the middle, rostral projection less prominent than in M. longa. 

 Lateral parts of last segment of metasome acutangular at the tip. Urosome 

 comparatively shorter than in M. longa, genital segment not attaining the length 

 of the other 2 combined. Caudal rami scarcely as long as the anal segment, 

 and of nearly uniform breadth throughout, outermost seta situated about in the 

 middle of the outer edge. Anterior antennae, when reflexed, reaching but slightly 

 beyond the anterior division of the body, structure about as in M. longa, except 

 that the dentiform projection is wanting in the 10th articulation. Last pair of 

 legs composed of only 3 joints, the last 2 being united. 



Male resembling that of M. longa, but having the cephalosome more 

 strongly vaulted above. Left anterior antenna (more rarely the right) genicnlate. 



16 Crustacea. 



