108 G. 0. SARS. CRUSTACEA. [NORW. POL. EXP. 



Description of the Female. 



The average length of the body in fully adult specimens is 0'70 mm. 

 Dr. Giesbrecht, on the other hand, gives the length as 0'95 mm., and this 

 difference in size might perhaps give rise to some doubt about the identity of 

 the 2 forms. As, however, in the next species also, the length given by Dr. 

 Giesbrecht considerably exceeds that of polar specimens, and, moreover, Dr. 

 Giesbrecht himself has proved, in the case of some other species, rather a 

 wide range of variation in this respect, no great stress can, in my opinion, 

 be laid upon this difference. 



The general form of the body (see figs. 1 & 2), as compared with that 

 of the other known species, is rather short and robust, subpyriform. The 

 anterior division is somewhat tumefied and, seen dorsally (fig. 1), of oblong 

 oval form, with the greatest width equal to about half the length, and occur- 

 ring rather in front of the middle. It is composed of 6 well-defined segments, 

 the 1st of which is much the largest, exceeding in length the 2 succeeding ones 

 combined, whereas the last segment is extremely small and sharply marked off 

 from the others, being, as in other Cydopoida, very movably connected with 

 the preceding one, so that it has more the appearance of belonging to the 

 posterior than to the anterior division. The cephalic segment is evenly 

 rounded anteriorly, and projects in front in a small deflexed rostral promi- 

 nence, behind which the lower edges of the segment form on each side a 

 perfectly even curve. 



The tail (see fig. 4) is scarcely half as long as the anterior division, and is 

 much narrower, sub-cylindric in form. It is composed of 4 segments, the 1st 

 of which, the genital segment, is much larger than all the others combined. 

 This segment is gradually somewhat dilated in front, and, unlike what is 

 generally the case, has the 2 genital orifices on the dorsal side. In a few 

 specimens, the 2 ovisacs were still adhering to them, each containing a very 

 limited number of ova, generally only 4. The anal segment is a little larger 

 than the next preceding one, and exhibits at the end dorsally a quad- 

 rangular, thin-skinned area, containing the anal orifice. The caudal rami are 

 rather small, not nearly twice as long as they are broad, and are separated 

 in the middle by a distinct interspace. Each ramus carries 5 setee, 4 of 

 which issue close together from the transversely truncated tip, the 5th from 



