38 G. 0. SARS. CRUSTACEA. [norw. pol. exp. 



Description of the Female. 

 (PL VII, VIII). 



The length of fully adult specimens, measured from the front to the end 

 of the caudal rami, amounts to about 5 mm., and this form is accordingly 

 very much larger than any of the previously described species belonging to 

 this family. 



The body (see PI. VII, figs. 1 & 2), as in other Calanoids, has the 

 anterior division very sharply marked off from the posterior, and of much 

 larger size, exhibiting an oblong oval, or more properly navicular form, the 

 greatest width occurring rather behind the middle. This division is composed 

 of 5 segments, the foremost of which is more than twice as long as all the 

 others combined, and more properly represents 2 coalesced segments, the 

 cephalic and 1st pedigerous ones. Anteriorly this segment is gradually nar- 

 rowed, and is surmounted in front by a very conspicuous median crest, 

 appearing, in a lateral view of the animal (fig. 2), as a narrowly rounded, 

 helmet-shaped expansion, projecting considerably beyond the rostral prominence. 

 The latter is but very slight, and carries at the tip 2 very small tentacular 

 appendages. From this prominence, on each side, a distinctly marked, some- 

 what flexuous line is seen extending obhquely back as far as the base of the 

 posterior maxillipeds, where it abruptly curves straight backwards. As far 

 as these lines are obHque, they constitute the inferior edges of the cephalic 

 part of the segment, and below them the soft ventral face is somewhat pro- 

 tuberant, exhibiting, about in the middle, the oral aperture, and on each side 

 the antennae and the several oral appendages. The remaining part of the seg- 

 ment is somewhat shorter than the cephalic part, but still nearly as long as 

 all the exposed pedigerous segments combined. Of these the 3 anterior 

 shghtly diminish in size, whereas the last is very small and imperfectly defined 

 from the preceding one. In the middle, this latter segment is deeply emargin- 

 ated, the lateral parts projecting behind as obtuse protuberances. 



The posterior division of the body, or the tail, is scarcely more than Vs 

 the length of the anterior, and is very much narrower, subcylindric in form. 

 It is composed (see fig. 9) of 4 well-defined segments, the 1st of which, or the 

 genital segment, is much the largest, though shorter than the 2 succeeding 

 ones combined. It is somewhat dilated in front, and forms below a slight 

 protuberance, carrying the genital opening. Of the succeeding segments, the 



