40 BRITISH COPEPODA. 



constitute no inconsiderable part of the food of the 

 whale. 



The three species, C. magnus, borealis, and elegans, 

 described by Sir John Lubbock (loc. cit.) from speci- 

 mens taken in the Arctic Seas, seem to be founded, 

 as pointed out to me by Mr. Norman, on different 

 stages of development of the present species. 



Having had no opportunity of seeing the old 

 descriptions given by Gunner and Leach, I here follow 

 M. Boeck who seems to have examined the literature 

 of the subject with much care. The conclusion is 

 that Gunner's description has been wholly misunder^ 

 stood or overlooked by modern writers ; his Monoculus 

 finmarchicus (which has usually been identified with the 

 Temora longicornis of the present monograph) being 

 really the species now under consideration, Calanus 

 finmarchicus. Leach's genus Calanus was established 

 in order to receive Gunner's species, though the name 

 has been used by recent authors (Dana, Lubbock, 

 Glaus) to include species wholly different. If this 

 view be correct it is only right that the term Calanus 

 should revert to the species for which it was first 

 proposed ; the genus CetocMlus being at the same time 

 discarded. 



Genus 2. METRIDIA, Boeck (1865). 



(? Pleuromma, Glaus.) 



Head separate from the first ring of the thorax, and 

 produced into a cloven rostrum : fourth and fifth 



