Calanoida. 

 Fam. Phaennidae. 



Gen. Xanthocalanus, Giesbr. 



Remarks. Of this genus, in addition to the 2 species originally recorded 

 by Giesbrecht from the Mediterranean, several new forms have been described 

 in recent time from the northern Ocean, some of them being, however, so 

 nearly related, the ones to the others, that they, without a very close examina- 

 tion, may easily be confounded. As moreover, owing to the great britlleness 

 of the appendages, most specimens obtained are more or less defective, the 

 determination of the species belonging to the present genus is connected with 

 no small difficulty. I have myself formerly, under the name X. borealis, con- 

 founded 3 different species. The one originally described by the present author 

 under that name from the Nansen Expedition is a true arctic form, which does 

 not occur off the coast of Norway. It has recently been identified, though 

 with some doubt, by Mr. With with X. hirtipes Vanhoeffen. The Norwegian 

 form recorded in Vol. IV of the present work as X. borealis is quite certainly 

 not identical with the arctic species, differing, as it does, both by its much 

 inferior size and by the rather unlike structure of the last pair of legs. I was 

 seduced to this erroneous identification by the occurrence in my material of 

 some few specimens, in which the last pair of legs, by the complete fusion 

 of the 2 outer joints and the presence of only 3 apical spines, exhibited a 

 certain resemblance to these appendages in the arctic form. These specimens 

 I supposed to be young, not yet fully developed females, and that accordingly 

 the last pair of legs changed their character according to age. This supposition 

 has, however, turned out to be quite wrong. I have subsequently found fully 

 adult specimens with the very same structure of the last pair of legs, and I 

 have convinced myself that they are referable to a well defined species, which 

 will be described below. For the other Norwegian species I propose the name 



