156 



small, each with 4 subequal apical setse. Anterior antennae more or less slender, 

 composed in female of 24 articulations, and in male transformed in much the 

 same manner as in Pseudocalanus. Posterior antennae and oral parts resembling 

 in structure those parts in the said genus. Posterior maxillipeds, however, more 

 slender, and having the terminal part reflexed. Natatory legs on the whole built 

 upon the same type as in Pseudocalanus. Last pair of legs in female wholly 

 absent, in male comparatively small and very asymmetrical, left leg slender, 

 6-articulate, right very small, 3-articulate, last joint not styliform. 



Remarks. As I stated on page 20, it is now my opinion that the small 

 Calanoid described from Nansen's Polar Expedition as Pseudocalanus pygmceus 

 should more properly be regarded as the type of a separate genus, for which 

 the name Microcalanus was proposed. The correctness of this view has now been 

 still further confirmed by the discovery off the Norwegian coast of another still 

 smaller Calanoid, which is evidently congeneric with the polar form, though ap- 

 parently specifically distinct. This form is described below. 



Microcalanus pusillus, G. 0. Sars, n. sp. 

 i. PI. ii, & PI. m, fig. i). 



Specific Characters. Female. General form of body resembling that of 

 M. pygmmus, the anterior division being rather tumid and, seen dorsally, of oval 

 form, greatest width almost attaining half the length, both extremities abruptly 

 contracted, the anterior one narrowly rounded at the tip. Cephalosome together 

 with the united 1st pedigerous segment occupying 2 / 3 of the anterior division, 

 dorsal margin evenly curved in front. Lateral lobes of last segment of metasome 

 somewhat appressed and rounded off at the tip. Urosome about equal in length 

 to 1 / 3 of the anterior division, genital segment conspicuously dilated in the 

 middle. Caudal rami scarcely longer than they are broad, apical setse of moderate 

 length, Eye wholly absent. Anterior antennae much shorter than in the typical 

 species, scarcely reaching, when reflexed, beyond the genital segment. Natatory 

 legs less slender than in M. pygmceus. terminal joint of outer ramus in 2nd to 

 4th pairs comparatively broader, with the apical spine remarkably dilated, cul- 

 tellate in shape, and very coarsely serrate outside. 



Male rather unlike the female in general appearance, the anterior division 

 being still shorter and more tumid, whereas the urosome is much more slender 

 than in female, fully equalling half the length of the anterior division. Anterior 

 antennas with the proximal part rather dilated and clothed anteriorly with large 



