98 



61. Idyopsis dilatata, G. 0. Sars, n. sp. 



(PI. LVii. fig. 1). 



Specific Characters. Female. Anterior division of body much dilated, 

 with the cephalic segment very largely expanded, and about twice as long as the 

 3 succeeding segments combined, lateral edges boldly curved, front bluntly 

 rounded. Epimeral plates rather narrow, acutangular at the tips. Last segment 

 of metasome extremely small, but wholly exposed. Urosome comparatively short, 

 not attaining half the length of the anterior division, genital segment rather large 

 and expanded, its lateral edges minutely indented in the middle and finely cili- 

 ated. Caudal rami about as long as they are broad, and obtusely truncated at 

 the tip; apical setse of moderate length. Eye well developed. Anterior antenna 1 

 comparatively slender, though not nearly attaining the length of the cephalic seg- 

 ment, 2nd joint much the largest, terminal part considerably shorter than the last 

 2 joints of the proximal part combined. Posterior antenna? with the first 2 joints 

 imperfectly defined, outer ramus 3-articulate. First pair of legs with the outer 

 ramus scarcely exceeding in length the 1st joint of the inner, and having all 3 

 joints of about equal size. Last pair of legs very narrow, with the proximal joint 

 scarcely at all expanded inside, distal joint narrow fusiform in outline, with one 

 of the marginal setae attached to about the middle of the outer edge. Ovisac 

 rounded, containing only a limited number of comparatively large ova. 



Body of a pale yellowish colour, with a slight rosy tinge; ovarial tubes 

 reddish brown, forming on each side, within the cephalic segment, a remarkably 

 large csecal dilatation. 



Length of adult female about half a millimetre (0.48 mm.). 



Remark*. This form may be easily recognised by the remarkably broad 

 and flattened cephalic segment, a character which has given rise to the specific 

 name here proposed. 



Occurrence. Some few female specimens of this species have been found 

 at different times off the west coast of Norway (Skjerjehavn, Sauesund) in depths 

 ranging from 10 to 30 fathoms. 



Distribution. Polar Islands north of Grinnell Land (2nd Fram Exped.). 





