86 



Occurrence.— The species has a distribution along the Norwegian coast 

 similar to that of 1. negleeta, and is generally found in company with that species. 

 It is, however, on the whole, less frequent, though in one locality, at Fser.cler, in 

 the outermost part of the Christiania Fjord, I found it in considerable abundance 

 among decaying alga?, in a depth of about 20 fathoms. 



Distribution. — British Isles (Sp. Bate), Kattegat. (Meinert). 



Fam. 2. Arcturidae. 



Characters. — Body narrow, scarcely at all depressed, approaching to a 

 cylindric form. Coxal plates small, though distinct. Metasome with the segments 

 more or less consolidated, the last one rather large. Superior antenna? small, 

 with the flagellum uniarticulate. Inferior antenna? very strongly developed, jiedi- 

 form, the outer joints of the peduncle being much elongated and connected by 

 geniculated bends, flagellum comparatively short. Oral parts on the whole re- 

 sembling those in the Idotheidce. The 4 anterior pairs of legs very unlike the 3 

 posterior ones, and not ambulatory, nor strictly prehensile; the 1st pair very 

 small and closely applied to the oral parts, so as to exhibit more the appearance 

 of maxillipeds; the 3 succeeding pairs of very feeble structure, and fringed with 

 long delicate seta?. The 3 posterior pairs of legs normally developed, and rather 

 strongly built, diminishing somewhat in length posteriorly. Pleopoda present in 

 the normal number, the 2 anterior pairs being natatory, with narrow and densely 

 setifcrous plates, the 3 posterior pairs exclusively branchial; 2nd pair in male 

 with a long bi-setose stylet appended to the inner plate. Uropoda, as in the Ido- 

 theidce, valve-like, arching over the lower face of the metasome, and having a small 

 secondary plate inside the terminal one. Male much smaller than female. 



Remarks. — In external appearance, the forms belonging to this family are 

 very unlike those of the preceding one, and were, indeed, by some of the earlier 

 authors, widely separated from them, and associated with a very different family, 

 viz., the Anthuridce. On a closer examination, however, they are, in fact, found 

 to show nothing in common with the latter family, except the narrow, cylindric 

 form of the body, whereas they exhibit a close relationship to the Idotheidce, both 

 as regards the structure of the oral parts, and that of the metasome. The chief 

 difference consists in the strong development of the inferior antenna?, and in the 



