50 



Body in both sexes rather pellucid, of an uniform whitish grey colour, 

 without any obvious pigment. 



Length of adult female 0.63 mm. 



Remarks. The present species is closely allied to H. gracilis Glaus, 

 but of somewhat smaller size, and on the whole of a rather more delicate 

 appearance. On a closer examination some well-marked differences are also 

 found in the structural details, as pointed out in the above diagnosis. 



Occurrence. I have met with this species in several places both on 

 the west and south coasts of Norway, but have formerly not been aware of 

 its specific difference from H. graeilis Glaus. It is only found in depths ranging 

 from 20 to 60 fathoms, never, as is the case with H. gracilis and most other 

 species of the present genus, in the littoral zone. 



Fam. Idyaeidae. 



Gen. Idyaea, Philippi (Idya). 

 39. Idyaaa graciloides, G. O. Sars, n. sp. 



(PI. XXXI). 



Specific Characters. Female. Body comparatively slender, resembling 

 somewhat in shape that of /. gracilis Scott. Cephalic segment about equalling 

 in length the 3 succeeding segments combined and rather broad behind; rostral 

 prominence very small. Epimeral plates of the 3 succeding segments laterally 

 expanded and closely contiguous. Last trunkal segment, as usual, very small 

 and without any distinct epimeral plates. Urosome about equalling in length 

 2 /3 of the anterior division and much narrower; genital segment fully as long 

 as the 3 succeeding segments combined and somewhat fusiform in outline, 

 being conspicuously dilated in the middle. Caudal rami about as long as they 

 are broad, and sub-quadrangular in form; apical setae very slender, the outer- 

 most and innermost ones rather thin and considerably longer than in /. gracilis. 

 Anterior antennae slender and elongated, exceeding somewhat in length the 

 cephalic segment, 3rd joint longer and narrower than the 2nd and about twice 

 the length of the 4th; terminal part, composed of the 4 outermost joints, 

 occupying about V* of the length of the antenna. Posterior antennae and oral 

 parts of the usual structure. 1st pair of legs resembling somewhat those in 



