80 G. 0. SARS. CRUSTACEA. [NORW. POL. EXP. 



male comparatively shorter, left antenna distinctly geniculate, but with the 

 part preceding the geniculation only slightly dilated. Posterior antennae, 

 mandibles, maxillae, and anterior maxillipeds about as in H. spinifrons. 

 Posterior maxillipeds very narrow, with the 1st basal joint much shorter than 

 the 2nd, and carrying, about in the middle of the anterior edge, an exceedingly 

 long and slender, flexuous spine, exceeding half the length of the maxilliped. 

 Last pair of legs in female with the incurved spine of the 2nd joint of the 

 outer ramus cultriform, and shorter than the terminal joint; those in male 

 with the 2nd basal joint of right leg produced inside to a falciform, ciliated 

 process, terminal joint of outer ramus in the right leg oblong lamellar, in the 

 left leg rounded, with a slender apical claw and 2 short lateral spines. 

 Length of adult female 4'56 mm., of male 4'20 mm. 



Remarks. This species is certainly very closely allied to H. spinifrons 

 of Glaus, but cannot, in my opinion, be regarded as identical with this species, 

 since it seems to differ not only in its much larger size, but also in some of 

 the structural details. The form recorded by Prof. Moebius from the North Sea 

 as H. spinifrons, Glaus, is unquestionably Boeck's species. 



Description of the Female. 



The average length of adult specimens is from 4'50 to 4'60 mm., and 

 there is no difference in this respect between polar and Norwegian specimens. 

 On the other hand, the length of H. spinifrons is indicated by Dr. Giesbrecht 

 to be only from 3'00 to 3'15 mm., and that of the other species to be far less. 

 The northern species accordingingly grows to a much larger size than does 

 any of the other known species. 



The general form of the body (figs. 1 & 2) is rather slender, with the 

 anterior division about twice the length of the posterior. Seen dorsally (fig. 1), 

 the former division exhibits a rather regular oblong oval form, with the 

 greatest width in the middle, and about equalling 2 /5 of the length. The 

 anterior extremity appears obtusely rounded, the posterior somewhat broader, 

 and slightly emarginated in the middle. On a closer inspection, the anterior 

 extremity is found to be surmounted in the middle by a sharply defined 

 knob-shaped prominence, which in a lateral view of the animal (figs. 2 & 3) 

 appears abruptly bent downwards, forming an angular rostrum. To the tip 

 of this rostrum, 2 very long and delicate, perfectly straight filaments are 



