NO. 6.] ACCOUNT OF THE SPECIES. 119 



Fam. OITHONID.E. 

 Gen. Oithona, Baird. 



Remarks. Of this genus, 2 distinct species occur off the Norwegian 

 coast, one of them being more than twice as large as the other. Boeck 

 records these 2 species under the names 0. spinifrons and 0. pygmcea. 

 The first-named form is most probably identical with 0. plumifera, Baird, 

 the 2nd with 0. helgolandica, Glaus, both these names having the priority 

 to those proposed by Boeck. In Dr. Giesbrecht's opinion, both the Norwegian 

 forms recorded by Boeck are identical with the Mediterranean species described 

 by Glaus as 0. similis. This is evidently erroneous, since, as stated above, 

 the 2 Norwegian forms are very distinct the one from the other. Nor can I 

 admit the assumption of Dr. Giesbrecht, that 0. helgolandica and 0. similis 

 are identical, as it seems hardly probable that Glaus would have described 

 the very same species under 2 different names. In the Polar Sea, this genus 

 is represented by a single species, which has turned out to be identical with 

 one of the 2 forms occurring off the Norwegian coast. 



27. Oithona helgolandica, Glaus. 



Syn : Oithona pygmcea, Boeck. 

 spinifrons, Brady (not Boeck). 



spinirostris, Giesbrecht (not Claus). 



Some few specimens of this form were found in 2 samples taken 

 October 12th and 13th, north of the New Siberian Islands. 



Distribution. Coast of Norway (very common), British Isles, Heligoland, 

 Bay of Kiel. 



Fam. MORMONILLID.K. 

 Gen. Mormonilla, Giesbrecht. 



Remarks. The systematic position of this remarkable genus, established 

 by Dr. Giesbrecht, appears somewhat doubtful, since only one sex, the 

 female one, is as yet known. I think, however, that Dr. Giesbrecht is quite 



1 I think the establishment of this family is necessary. Dr. Giesbrecht refers the 

 genus Oithona to the family Cydopidce, 



