426 



Occurrence. - Off the coast of Norway, this species would seem to be 

 wholly restricted to the arctic region, being found occasionally off the Finmark 

 coast, in depths ranging from 50 to 100 fathoms. 



Distribution. Arctic Ocean, widely distributed: Greenland (Hansen), 

 Spitsbergen (Goes), Arctic America (Lepechin), Labrador (Packard), Jan Mayen 

 (Norw. North Atl. Exp.), Franz Joseph's Land (Heller), the Barents Sea 

 (Hoek), the White Sea (Lepechin), the Kara Sea (Stuxberg), the Siberian 

 Polar Sea (Stuxberg). 



7. Rhachotropis Helleri, Boeck. 



(PL 150). 

 Tritropis Helleri, Boeck, Crust, amph. bor. & arct. p. 79. 



Body considerably more slender than in the preceding species, and 

 having the subdorsal keels restricted to the metasome only. The first 3 

 segments of mesosome with the posterior edge slightly raised dorsally; last 

 segment of mesosome and those of metasome each with a distinct, though not 

 very large dorsal projection, the posterior one much smaller and more obtuse 

 than the 2 preceding ones; projections of the subdorsal keels well-defined. 

 First segment of urosome produced at the end dorsally to a single acuminate 

 projection. Cephalon about the length of the first 2 segments of mesosome 

 combined, and evenly vaulted above, rostral projection quite short, lateral 

 corners narrow triangular, and defined posteriorly by a rectangular incision. 

 First pair of coxal plates narrowly produced anteriorly, with the distal edge 

 straight, and none of the corners pointed; the 2 succeeding pairs rounded, with 

 the posterior corner somewhat angular; 4th pair a little broader than the 

 preceding ones and slightly emarginated posteriorly; penultimate and ante- 

 penultimate pairs without any lateral ridge. Last pair of epimeral plates of 

 metasome with the posterior edge evenly curved and serrated throughout. 

 Eyes rather large, rounded oval in form, with the visual elements distinct, 

 though somewhat less conspicuous than in the preceding species, pigment light 

 brown. Antennae in female considerably less elongated than in II. acideata, 

 and carrying scattered, partly plumose setse; the superior ones scarcely 

 exceeding l /a of the length of the body, 1st joint of the peduncle not attaining 

 the length of the other 2 combined, last joint about half as long as the 

 penultimate one, both edged inside with calceolee, flagellum scarcely exceeding 

 the length of the peduncle, and composed of 12 15 articulations only, each 

 carrying a small calceola. Same antennae in male more than twice as long as 

 in female, with the flagellum very slender and elongated, and provided at the 



