the said species, the innermost but one scarcely attaining half the length of the 

 urosome, seta of the outer edge placed near the tip, and, like the outermost of 

 the apical setse, reduced to a small, knob-like spine. Anterior antennae with the 

 2nd joint somewhat shorter than in T. longimana, terminal part nearly half the 

 length of the proximal part. Posterior maxillipeds less powerfully developed than 

 in that species, with the hand less dilated and the palm only slightly concaved, 

 being defined in front by an obtuse angle. First pair of legs resembling in struc- 

 ture those in T. longimcma, but with the rami somewhat narrower, apical claws 

 scarcely at all denticulate. Last pair of legs well developed, though not nearly 

 as large as in T. longimana, extending only somewhat beyond the middle of the 

 genital segment, distal joint rounded oval in form and somewhat exserted at the 

 tip, inner expansion of the proximal joint broadly rounded at the end, and scarcely 

 extending as far as the distal joint; marginal setse of both joints comparatively 

 more elongated, some of them spiniform and minutely ciliated. 



Male differing from the female in a manner analogous to that in the 

 preceding species. Last pair of legs rather similar, but having the distal joint 

 more attenuated towards the end, and the inner expansion of the proximal joint 

 still shorter, with the 3 marginal setae very unequal, the middle one being much 

 elongated, whereas the outermost one is much reduced in size. 



Colour of body, except the dorsal face of the cephalic segment, very dark 

 bluish grey or almost black. 



Length of adult female 1.50 mm. 



Remarks. This form was first figured (but not described) by Kr0yer in 

 the above-quoted work as Harpacticus gilbus. It was subsequently described by 

 Th. Scott as a new species under the name of Thalestris polaris, he not having 

 been aware of the fairly recognizable figures given of this species by Kr0yer. It 

 is nearly allied to T. longimana, though easily distinguishable by its more slender 

 form, and especially by the much more produced caudal rami. When alive, it 

 is also recognized at once by the very dark colour of its body. 



Occurrence. I have found this form in several localities on the west coast 

 of Norway, and northwards along the whole Finmark coast as far as Vads0. In 

 some places it occurred in great numbers on a muddy bottom covered with de- 

 caying algae, the depth being about 20 fathoms. 



Distribution. Franz Josef Land (Scott). 



