100 



Posterior antennae comparatively slender, 3-articulate, with the outer ramus short, 

 inarticulate. Mandibles, maxillae and anterior maxillipeds resembling in structure 

 those parts in Idyopsis. Posterior maxillipeds, however, much more slender, and 

 having a very movable articulation between the first 2 joints, last joint carrying 

 an elongated claw accompanied by 2 or 3 slender setae. First pair of legs with 

 the outer ramus about as in Idyopsis, inner ramus, however, only composed of 2 

 joints very movably articulated together, the last one carrying outside 3 short 

 setse and at the tip 2 very slender claws. Natatory legs with the rami rather 

 slender and subequal in length, middle joint of inner ramus carrying in the 2 

 anterior pairs 2 setae, in the posterior pair 1. Last pair of legs slender and, as 

 in Idyopsis, extended laterally. 



Remarks. This genus is nearly allied to Idyopsis, but differs in some 

 particulars, especially as regards the structure of the posterior maxillipeds and 

 that of the 1st pair of legs. Of this genus also, 2 well-defined species have been 

 found off the Norwegian coast. 



63. Idyella pallidula, G. 0. Sars, n. sp. 



(PI. LVIII, fig. 1). 



Specific Characters. Female. Anterior divisioli of body rather broad and 

 depressed; seen dorsally. oval fusiform in outline, with the greatest width some- 

 what behind the middle. Cephalic segment very large, about twice as long as 

 the 3 succeeding segments combined, and gradually tapering anteriorly, front 

 conically produced. Epimeral plates sub-contiguous, obtuse at the tips. Last 

 segment of metasome very small. Urosome not attaining half the length of the 

 anterior division, genital segment produced on each side, somewhat in front of 

 the middle, to an obliquely posteriorly-pointing triangular lobe; 2nd segment 

 simple. Caudal rami short, with the usual number of setae, one of them issuing 

 from the middle of the outer edge, the 2 middle apical setae rather slender. Eye 

 wholly absent. Anterior antennae scarcely attaining half the length of the cephalic 

 segment and clothed with comparatively short setae, 2nd joint the largest, terminal 

 part about the length of the 2 preceding joints combined. Posterior maxillipeds 

 with the middle joint scarcely at all dilated, sublinear in form. First pair of 

 legs with the outer ramus much curved and somewhat exceeding half the length 

 of the inner, proximal joint of the latter rather broad, lamellar, with a strong 

 plumose seta in- the middle of the inner edge, distal joint much narrower than 

 the proximal one, and more than half its length. Last pair of legs very narrow, 



