51 



/. gracilis, the distal joint of the inner ramus being very narrow, though less 

 elongated than in that species, only slightly exceeding in length the proximal 

 joint. The 3 succeeding pairs of legs of quite normal appearance. Last pair 

 of legs much smaller than in /. gracilis, with the distal joint rather narrow, 

 sub-linear in form, and less densely hairy, all the setae issuing from the outer- 

 most part of the joint. 



Male of nearly same size as female, but comparatively still more 

 slender, with the urosome distinctly 5-articulate. Anterior antennae only slightly 

 transformed, being a little thicker than in female, with a small joint intercalated 

 between the 3rd and 4th; hinge rather imperfect. 2nd pair of legs with none 

 of the setae transformed. Last pair of legs much reduced in size. 



Colour of the living animal not yet ascertained. 



Length of adult female 0.86 mm. 



Remarks. This form is nearest allied to /. gracilis Scott, but is 

 evidently specifically distinct, differing in the comparatively less produced caudal 

 rami, as also rather conspicuously in the structure of the anterior antennae and 

 the last pair of legs. 



Occurrence. Several specimens of this form were picked up from 

 samples taken at Korshavn from a depth of about 60 fathoms, muddy sand. 

 I have not met with it in other places on the Norwegian coast. 



40. Idyaea compacta, G. O. Sars, n. sp. 



(PI. XXXII). 



Specific Characters. Female. Body unusually short and compact, with 

 the anterior division rather broad and somewhat depressed. Cephalic segment 

 considerably exceeding in length the exposed part of the trunk, and only very 

 slightly contracted in front. Epimeral plates of the 3 succeeding segments con- 

 siderably expanded laterally and closely contiguous, sub-imbricate. Last trunkal 

 segment, as usual, much narrower than the preceding ones, and without any 

 epimeral plates. Urosome unusually short, only sligtly exceeding in length Va of 

 the anterior division, its segments scarcely at all spinulose at the lateral corners, 

 and densely crowded. Anal opercle rather prominent, semilunar, and coarsely 

 denticulated at the edge. Caudal rami scarcely as long as they are broad at 

 the base, and somewhat obliquely truncated at the end, the outer corner being 

 the more prominent; apical setae very slender and elongated, the innermost 

 but one almost attaining the length of the whole body; innermost and outer- 

 most setae much thinner than the 2 middle ones and rather prolonged; seta 



