97 



ably more elongated than the Norwegian species. Well-marked differences also 

 seem to exist between the 2 species fn the structure of the 1st and last pair 



of legs. 



Occurrence. Several specimens of this interesting form were found in 

 some samples kindly forwarded to me by Mr. Nordgaard, who took them off 

 the Finmark coast, partly at Repvaag, partly at Mehavn. Farther south this 

 species does not seem to occur, being in all probability a true arctic form. 



Gen. 25. IdyOpSlS, G. 0. Sars, n. 



Generic Characters. Body short and depressed, somewhat resembling in 

 form that in Idya, the anterior division being more or less expanded, the poste- 

 rior abruptly much narrower. Rostral projection small, not defined at the base. 

 Anterior antennae not much elongated, 8-articulate, sensory filament of 4th joint 

 much smaller than in Idya. Posterior antennae with the outer ramus well devel- 

 oped, 3- or 4-articulate. Anterior lip of usual form. Mandibles with the palp 

 rather fully developed, biramous. Maxillae of quite normal structure, the epipodal 

 lobe being well defined. Anterior maxillipeds of rather compact form, with all 

 the lateral lobes distinctly developed, the outermost armed with one or two strong 

 claws; terminal part distinct, 3-articulate, setiferous. Posterior maxillipeds well 

 developed, 3-articulate, carrying on the tip 3 strong claws. First pair of legs 

 with the outer ramus much shorter than the inner, and somewhat resembling that 

 in Idya, the lateral and apical spines being provided along the outer part of 

 one edge with slender cilia, inner ramus distinctly 3-articulate, with the 1st joint 

 rather large, the other 2 much smaller and subequal in size, last joint carrying 

 2 slender claws on the tip, and inside 2 short setae. Natatory legs resembling 

 in structure those in Idya, middle joint of inner ramus, however, in the posterior 

 pair with only a single seta. Last pair of legs, as in Idya, extended laterally, 

 distal joint narrow and elongated. 



Remarks. This new genus somewhat resembles Idya, as regards the 

 general form and composition of the body, but differs rather essentially in some 

 of the anatomical details, especially in the structure of the oral parts. Two well- 

 defined species of this genus occur off the Norwegian coast. 



Crustacea. 



