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



spine of the terminal joint, the inner one in having only 2 natatory setae 

 inside the last joint ^. 



The 4th pair of legs (fig. 12) have the outer ramus exactly as in the 3rd 

 pair, ^\'hereas the inner ramus is much narrower, and projects considerably 

 beyond the outer. This ramus also differs in having only a single natatory 

 seta inside the terminal joint, attached at a short distance from its base. 



The last pair of legs (see figs. 13 & 14), as in other Cyclopoida, are 

 very small and simple in structure, issuing somewhat laterally from the 

 basal segment of the trunk. In most other Cyclopoida the legs of this pair 

 are biarticulate ; but in the present form, the proximal joint is completely 

 consolidated with the segment, and is only indicated by the slender bristle 

 belonging to it, which in this case issues from the segment itself, outside the 

 base of the distal joint. The latter is rather unlike that in the other known 

 species of this genus, forming a slender cylindric piece provided at the tip with 

 2 subequal setae. This piece extends obliquely upwards, so as to project 

 dorsally, when the animal is viewed laterally (fig. 2): hence the specific 

 name notopus, proposed by Dr. Giesbrecht for this species. 



The adult male is much smaller than the female, and on the whole 

 resembles that of the next species (conf. fig. 15). It is easily to be distinguished 

 from the female by the more powerfully developed posterior maxillipeds, and 

 by the structure of the tail. The latter is composed of 5 well-defined seg- 

 ments, the 1st of which, the genital segment, is greatly tumefied, and gener- 

 ally contains, within its lateral parts, 2 vesicular spermatophores ready to be 

 evacuated. During copulation, the male grasps the female with his powerful 

 posterior maxillipeds dorsally at the boundary between the last segment of 

 the trunk and the genital segment; the 2 sexes are not infrequently found 

 locked together in this manner even after having been preserved in alcohol 

 (conf. fig. 15). 



Occurrence. This form occurred very abundantly in some samples 

 taken on the 13th October, 1893, north of the New Siberian Islands, the tow- 

 net having been lowered to a depth of 50 metres. 



Distribution. Pacific Ocean, between 90° and 124° W., W N. and 3° S., 

 down to 1000 metres (Giesbrecht). 



1 In the figure here given, 3 such setee are, hy a mistake, delineated. 



